rgpio(3)

NAME
rgpio - A C library to manipulate a remote SBC's GPIO.

SYNOPSIS
#include <rgpio.h> gcc -Wall -o prog prog.c -lrgpio ./prog

DESCRIPTION
rgpio is a C library which allows remote control of the GPIO and other functions of Linux SBCs running the rgpiod daemon.
The rgpiod daemon must be running on the SBCs you wish to control.

  Features
o reading and writing GPIO singly and in groups
o software timed PWM and waves
o GPIO callbacks
o pipe notification of GPIO alerts
o I2C wrapper
o SPI wrapper
o serial link wrapper
o simple file handling
o creating and running scripts on the rgpiod daemon
o a simple interface to start and stop new threads

  Usage
Include <rgpio.h> in your source files.
Assuming your source is in prog.c use the following command to build
    gcc -Wall -o prog prog.c -lrgpio
to run make sure the rgpiod daemon is running
    rgpiod&
     ./prog
For examples see the lg archive file.

  Notes
All the functions which return an int return < 0 on error

OVERVIEW

  ESSENTIAL
rgpiod_start Connects to a rgpiod daemon
rgpiod_stop Disconnects from a rgpiod daemon

  FILES
file_open Opens a file
file_close Closes a file
file_read Reads bytes from a file
file_write Writes bytes to a file
file_seek Seeks to a position within a file
file_list List files which match a pattern

  GPIO
gpiochip_open Opens a gpiochip device
gpiochip_close Closes a gpiochip device
gpio_get_chip_info Gets gpiochip information
gpio_get_line_info Gets gpiochip line information
gpio_get_mode Gets the mode of a GPIO
gpio_claim_input Claims a GPIO for input
gpio_claim_output Claims a GPIO for output
gpio_claim_alert Claims a GPIO for alerts
gpio_free Frees a GPIO
group_claim_input Claims a group of GPIO for inputs
group_claim_output Claims a group of GPIO for outputs
group_free Frees a group of GPIO
gpio_read Reads a GPIO
gpio_write Writes a GPIO
group_read Reads a group of GPIO
group_write Writes a group of GPIO
tx_pulse Starts pulses on a GPIO
tx_pwm Starts PWM on a GPIO
tx_servo Starts servo pulses on a GPIO.
tx_wave Starts a wave on a group of GPIO
tx_busy See if tx is active on a GPIO or group
tx_room See if more room for tx on a GPIO or group
gpio_set_debounce_time Sets the debounce time for a GPIO
gpio_set_watchdog_time Sets the watchdog time for a GPIO
callback Starts a GPIO callback
callback_cancel Stops a GPIO callback

  I2C
i2c_open Opens an I2C device
i2c_close Closes an I2C device
i2c_write_quick smbus write quick
i2c_read_byte smbus read byte
i2c_write_byte smbus write byte
i2c_read_byte_data smbus read byte data
i2c_write_byte_data smbus write byte data
i2c_read_word_data smbus read word data
i2c_write_word_data smbus write word data
i2c_read_block_data smbus read block data
i2c_write_block_data smbus write block data
i2c_read_i2c_block_data smbus read I2C block data
i2c_write_i2c_block_data smbus write I2C block data
i2c_read_device Reads the raw I2C device
i2c_write_device Writes the raw I2C device
i2c_process_call smbus process call
i2c_block_process_call smbus block process call
i2c_zip Performs multiple I2C transactions

  NOTIFICATIONS
notify_open Request a notification handle
notify_close Close a notification
notify_pause Pause notifications
notify_resume Start notifications for selected GPIO

  SCRIPTS
script_store Store a script
script_run Run a stored script
script_update Set a scripts parameters
script_status Get script status and parameters
script_stop Stop a running script
script_delete Delete a stored script

  SERIAL
serial_open Opens a serial device
serial_close Closes a serial device
serial_read_byte Reads a byte from a serial device
serial_write_byte Writes a byte to a serial device
serial_read Reads bytes from a serial device
serial_write Writes bytes to a serial device
serial_data_available Returns number of bytes ready to be read

  SHELL
shell Executes a shell command

  SPI
spi_open Opens a SPI device
spi_close Closes a SPI device
spi_read Reads bytes from a SPI device
spi_write Writes bytes to a SPI device
spi_xfer Transfers bytes with a SPI device

  THREADS
thread_start Start a new thread
thread_stop Stop a previously started thread

  UTILITIES
lgu_get_sbc_name Get the SBC name
lgu_get_internal Get a SBC configuration value
lgu_set_internal Set a SBC configuration value
lgu_time Returns the number of seconds since the epoch
lgu_timestamp Returns the number of nanoseconds since the epoch
lgu_sleep Sleeps for a number of seconds
lgu_set_user Set the user (and associated permissions)
lgu_set_share_id Set the share id for a resource
lgu_use_share_id Use this share id when asking for a resource
lgu_rgpio_version Get the rgpio library version
lgu_error_text Get the error text for an error code

FUNCTIONS

int rgpiod_start(const char *addrStr, const char *portStr)

    Connect to the rgpiod daemon. Reserving command and notification streams.
        addrStr: specifies the host or IP address of the SBC running the
                 rgpiod daemon.  It may be NULL in which case localhost
                 is used unless overridden by the LG_ADDR environment
                 variable.
        portStr: specifies the port address used by the SBC running the
                 rgpiod daemon.  It may be NULL in which case "8889"
                 is used unless overridden by the LG_PORT environment
                 variable.
    If OK returns a sbc (>= 0).
    On failure returns a negative error code.
    This sbc value is passed to the other functions to specify the SBC to be used.
    If the LG_USER environment variable exists that user will be "logged in" using lgu_set_user. This only has an effect if the rgpiod daemon is running with access control enabled.

void rgpiod_stop(int sbc)

    Terminates the connection to a rgpiod daemon and frees resources used by the library.
        sbc: >= 0 (as returned by rgpiod_start).

int file_open(int sbc, const char *file, int mode)

    This function returns a handle to a file opened in a specified mode.
    This is a privileged command. See permits.
         sbc: >= 0 (as returned by rgpiod_start).
        file: the file to open.
        mode: the file open mode.
    If OK returns a handle (>= 0).
    On failure returns a negative error code.
    File
    A file may only be opened if permission is granted by an entry in the [files] section of the permits file. This is intended to allow remote access to files in a controlled manner.
    Mode
    The mode may have the following values.
    Macro Value Meaning
    LG_FILE_READ 1 open file for reading
    LG_FILE_WRITE 2 open file for writing
    LG_FILE_RW 3 open file for reading and writing
    The following values may be or'd into the mode.
    Macro Value Meaning
    LG_FILE_APPEND 4 Writes append data to the end of the file
    LG_FILE_CREATE 8 The file is created if it doesn't exist
    LG_FILE_TRUNC 16 The file is truncated
    Newly created files are owned by the user who launched the daemon with permissions owner read and write.
    Example
        #include <stdio.h>
        #include <rgpio.h>
        int main(int argc, char *argv[])
        {
           int sbc, handle, c;
           char buf[60000];
           sbc = rgpiod_start(NULL, NULL);
           if (sbc < 0) return 1;
           handle = file_open(sbc, "/ram/lg.c", LG_FILE_READ);
           if (handle >= 0)
           {
              while ((c=file_read(sbc, handle, buf, sizeof(buf)-1)))
              {
                 buf[c] = 0;
                 printf("%s", buf);
              }
              file_close(sbc, handle);
           }
           rgpiod_stop(sbc);
        }

int file_close(int sbc, int handle)

    This function closes the file.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by file_open).
    If OK returns 0.
    On failure returns a negative error code.
    Example
        file_close(sbc, handle);

int file_write(int sbc, int handle, const char *buf, int count)

    This function writes count bytes from buf to the the file.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by file_open).
           buf: the array of bytes to write.
         count: the number of bytes to write.
    If OK returns 0.
    On failure returns a negative error code.
    Example
        if (file_write(sbc, handle, buf, 100) == 0)
        {
           // file written okay
        }
        else
        {
           // error
        }

int file_read(int sbc, int handle, char *buf, int count)

    This function reads up to count bytes from the the file.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by file_open).
           buf: an array to receive the read data.
         count: the maximum number of bytes to read.
    If OK returns the count of bytes read and updates buf.
    On failure returns a negative error code.
    Example
           bytes = file_read(sbc, handle, buf, sizeof(buf));
           if (bytes >= 0)
           {
              // process read data
           }

int file_seek(int sbc, int handle, int32_t seekOffset, int seekFrom)

    This function seeks to a position within the file.
               sbc: >= 0 (as returned by rgpiod_start).
            handle: >= 0 (as returned by file_open).
        seekOffset: the number of bytes to move.  Positive offsets
                    move forward, negative offsets backwards.
          seekFrom: one of LG_FROM_START (0), LG_FROM_CURRENT (1),
                    or LG_FROM_END (2).
    If OK returns the new file position.
    On failure returns a negative error code.
    Example
        file_seek(sbc, handle, 123, LG_FROM_START); // Start plus 123
        size = file_seek(sbc, handle, 0, LG_FROM_END); // End, return size
        pos = file_seek(sbc, handle, 0, LG_FROM_CURRENT); // Current position

int file_list(int sbc, const char *fpat, char *buf, int count)

    This function returns a list of files which match a pattern.
          sbc: >= 0 (as returned by rgpiod_start).
         fpat: file pattern to match.
          buf: an array to receive the matching file names.
        count: the maximum number of bytes to read.
    If OK returns the count of bytes read and updates buf with the matching filenames (the filenames are separated by newline characters).
    On failure returns a negative error code.
    Example
        #include <stdio.h>
        #include <rgpio.h>
        int main(int argc, char *argv[])
        {
           int sbc, handle, c;
           char buf[60000];
           sbc = rgpiod_start(NULL, NULL);
           if (sbc < 0) return 1;
           c = file_list(sbc, "/ram/p*.c", buf, sizeof(buf));
           if (c >= 0)
           {
              buf[c] = 0;
              printf("%s", buf);
           }
           rgpiod_stop(sbc);
        }

int gpiochip_open(int sbc, int gpioDev)

    This returns a handle to a gpiochip device.
    This is a privileged command. See permits.
            sbc: >= 0 (as returned by rgpiod_start).
        gpioDev: >= 0
    If OK returns a handle (>= 0).
    On failure returns a negative error code.
    Example
        h = gpiochip_open(sbc, 0); // open gpiochip0
        if (h >= 0)
        {
           // open ok
        }
        else
        {
           // open error
        }

int gpiochip_close(int sbc, int handle)

    This closes a gpiochip device.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
    If OK returns 0.
    On failure returns a negative error code.
    Example
        status = gpiochip_close(sbc, h); // close gpiochip
        if (status < 0)
        {
           // close failed
        }

int gpio_get_chip_info(int sbc, int handle, lgChipInfo_p chipInfo)

    This returns summary information of an opened gpiochip.
             sbc: >= 0 (as returned by rgpiod_start).
          handle: >= 0 (as returned by gpiochip_open).
        chipInfo: address to store returned chip info.
    If OK returns a list of okay status, number of lines, name, and label.
    On failure returns a negative error code.

int gpio_get_line_info(int sbc, int handle, int gpio, lgLineInfo_p lineInfo)

    This returns detailed information of a GPIO of an opened gpiochip.
             sbc: >= 0 (as returned by rgpiod_start).
          handle: >= 0 (as returned by gpiochip_open).
            gpio: the GPIO.
        lineInfo: address to store returned line info.
    If OK returns a list of okay status, offset, line flags, name, and user.
    The meaning of the line flags bits are as given for the mode by gpio_get_mode.
    On failure returns a negative error code.

int gpio_get_mode(int sbc, int handle, int gpio)

    This returns the mode of a GPIO.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
          gpio: the GPIO to be read.
    If OK returns the mode of the GPIO.
    On failure returns a negative error code.
    Bit Value Meaning
    0 1 Kernel: In use by the kernel
    1 2 Kernel: Output
    2 4 Kernel: Active low
    3 8 Kernel: Open drain
    4 16 Kernel: Open source
    5 32 Kernel: Pull up set
    6 64 Kernel: Pull down set
    7 128 Kernel: Pulls off set
    8 256 LG: Input
    9 512 LG: Output
    10 1024 LG: Alert
    11 2048 LG: Group
    12 4096 LG: ---
    13 8192 LG: ---
    14 16384 LG: ---
    15 32768 LG: ---
    16 65536 Kernel: Input
    17 1<<17 Kernel: Rising edge alert
    18 1<<18 Kernel: Falling edge alert
    19 1<<19 Kernel: Realtime clock alert
    The LG bits are only set if the query was made by the process that owns the GPIO.

int gpio_claim_input(int sbc, int handle, int lFlags, int gpio)

    This claims a GPIO for input.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
        lFlags: line flags for the GPIO.
          gpio: the GPIO to be claimed.
    If OK returns 0.
    On failure returns a negative error code.
    The line flags may be used to set the GPIO as active low, open drain, open source, pull up, pull down, pull off.
    Example
        status = gpio_claim_input(sbc, h, 0, 23); // open GPIO 23 for input

int gpio_claim_output(int sbc, int handle, int lFlags, int gpio, int value)

    This claims a GPIO for output.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
        lFlags: line flags for the GPIO.
          gpio: the GPIO to be claimed.
         value: the initial value for the GPIO.
    If OK returns 0.
    On failure returns a negative error code.
    The line flags may be used to set the GPIO as active low, open drain, open source, pull up, pull down, pull off.
    If value is zero the GPIO will be initialised low (0). If any other value is used the GPIO will be initialised high (1).
    Example
        status = gpio_claim_output(sbc, h, 0, 35, 1); // open GPIO 35 for high output

int gpio_free(int sbc, int handle, int gpio)

    This frees a GPIO.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
          gpio: the GPIO to be freed.
    If OK returns 0.
    On failure returns a negative error code.
    The GPIO may now be claimed by another user or for a different purpose.

int group_claim_input(int sbc, int handle, int lFlags, int count, const int *gpios)

    This claims a group of GPIO for inputs.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
        lFlags: line flags for each GPIO.
         count: the number of GPIO to claim.
         gpios: the group GPIO.
    If OK returns 0.
    On failure returns a negative error code.
    The line flags may be used to set the group as active low, open drain, open source, pull up, pull down, pull off.
    gpios is an array of one or more GPIO. The first GPIO in the array is called the group leader and is used to reference the group as a whole.

int group_claim_output(int sbc, int handle, int lFlags, int count, const int *gpios, const int *values)

    This claims a group of GPIO to be used as outputs.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
        lFlags: line flags for each GPIO.
         count: the number of GPIO to claim.
         gpios: the group GPIO.
        values: the initial value for each GPIO.
    If OK returns 0.
    On failure returns a negative error code.
    The line flags may be used to set the group as active low, open drain, open source, pull up, pull down, pull off.
    gpios is an array of one or more GPIO. The first GPIO in the array is called the group leader and is used to reference the group as a whole.
    values is a list of initialisation values for the GPIO. If a value is zero the corresponding GPIO will be initialised low (0). If any other value is used the corresponding GPIO will be initialised high (1).

int group_free(int sbc, int handle, int gpio)

    This frees all the group GPIO.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
          gpio: the group leader.
    If OK returns 0.
    On failure returns a negative error code.
    The GPIO may now be claimed by another user or for a different purpose.

int gpio_read(int sbc, int handle, int gpio)

    This returns the level of a GPIO.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
          gpio: the GPIO to be read.
    If OK returns 0 (low) or 1 (high).
    On failure returns a negative error code.
    This command will work for any claimed GPIO (even if a member of a group). For an output GPIO the value returned will be that last written to the GPIO.

int gpio_write(int sbc, int handle, int gpio, int value)

    This sets the level of an output GPIO.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
          gpio: the GPIO to be written.
         value: the value to write.
    If OK returns 0.
    On failure returns a negative error code.
    This command will work for any GPIO claimed as an output (even if a member of a group).
    If level is zero the GPIO will be set low (0). If any other value is used the GPIO will be set high (1).

int group_read(int sbc, int handle, int gpio, uint64_t *groupBits)

    This returns the levels read from a group.
              sbc: >= 0 (as returned by rgpiod_start).
           handle: >= 0 (as returned by gpiochip_open).
             gpio: the offset of a member of the GPIO group to be read.
        groupBits: a pointer to a 64-bit memory area for the returned value.
    If OK returns the group size and updates groupBits.
    On failure returns a negative error code.
    This command will work for an output group as well as an input group. For an output group the value returned will be that last written to the group GPIO.
    Note that this command will also work on an individual GPIO claimed as an input or output as that is treated as a group with one member.
    After a successful read groupBits is set as follows.
    Bit 0 is the level of the group leader. Bit 1 is the level of the second GPIO in the group. Bit x is the level of GPIO x+1 of the group.

int group_write(int sbc, int handle, int gpio, uint64_t groupBits, uint64_t groupMask)

    This sets the levels of an output output group.
              sbc: >= 0 (as returned by rgpiod_start).
           handle: >= 0 (as returned by gpiochip_open).
             gpio: the offset of a member of the GPIO group to be written.
        groupBits: the level to set if the corresponding bit in groupMask is set.
        groupMask: a mask indicating the group GPIO to be updated.
    If OK returns 0.
    On failure returns a negative error code.
    The values of each GPIO of the group are set according to the bits of group_bits.
    Bit 0 sets the level of the group leader. Bit 1 sets the level of the second GPIO in the group. Bit x sets the level of GPIO x+1 in the group.
    However this may be overridden by the group_mask. A GPIO is only updated if the corresponding bit in the mask is 1.

int tx_pulse(int sbc, int handle, int gpio, int pulse_on, int pulse_off, int pulse_offset, int pulse_cycles)

    This starts software timed pulses on an output GPIO.
                 sbc: >= 0 (as returned by rgpiod_start).
              handle: >= 0 (as returned by gpiochip_open).
                gpio:  GPIO to be written.
            pulse_on: pulse high time in microseconds.
           pulse_off: pulse low time in microseconds.
        pulse_offset: offset from nominal pulse start position.
        pulse_cycles: the number of pulses to be sent, 0 for infinite.
    If OK returns the number of entries left in the PWM queue for the GPIO.
    On failure returns a negative error code.
    If both pulse_on and pulse_off are zero pulses will be switched off for that GPIO. The active pulse, if any, will be stopped and any queued pulses will be deleted.
    Each successful call to this function consumes one PWM queue entry.
    pulse_cycles cycles are transmitted (0 means infinite). Each cycle consists of pulse_on microseconds of GPIO high followed by pulse_off microseconds of GPIO low.
    PWM is characterised by two values, its frequency (number of cycles per second) and its duty cycle (percentage of high time per cycle).
    The set frequency will be 1000000 / (pulse_on + pulse_off) Hz.
    The set duty cycle will be pulse_on / (pulse_on + pulse_off) * 100 %.
    E.g. if pulse_on is 50 and pulse_off is 100 the frequency will be 6666.67 Hz and the duty cycle will be 33.33 %.
    pulse_offset is a microsecond offset from the natural start of the pulse cycle.
    For instance if the PWM frequency is 10 Hz the natural start of each cycle is at seconds 0, then 0.1, 0.2, 0.3 etc. In this case if the offset is 20000 microseconds the cycle will start at seconds 0.02, 0.12, 0.22, 0.32 etc.
    Another pulse command may be issued to the GPIO before the last has finished.
    If the last pulse had infinite cycles then it will be replaced by the new settings at the end of the current cycle. Otherwise it will be replaced by the new settings when all its cycles are compete.
    Multiple pulse settings may be queued in this way.

int tx_pwm(int sbc, int handle, int gpio, float pwmFrequency, float pwmDutyCycle, int pwmOffset, int pwmCycles)

    This starts software timed PWM on an output GPIO.
                 sbc: >= 0 (as returned by rgpiod_start).
              handle: >= 0 (as returned by gpiochip_open)
                gpio: the GPIO to be pulsed
        pwmFrequency: PWM frequency in Hz (0=off, 0.1-10000)
        pwmDutyCycle: PWM duty cycle in % (0-100)
           pwmOffset: offset from nominal pulse start position
           pwmCycles: the number of pulses to be sent, 0 for infinite
    If OK returns the number of entries left in the PWM queue for the GPIO.
    On failure returns a negative error code.
    Each successful call to this function consumes one PWM queue entry.
    PWM is characterised by two values, its frequency (number of cycles per second) and its duty cycle (percentage of high time per cycle).
    Another PWM command may be issued to the GPIO before the last has finished.
    If the last pulse had infinite cycles then it will be replaced by the new settings at the end of the current cycle. Otherwise it will be replaced by the new settings when all its cycles are compete.
    Multiple PWM settings may be queued in this way.

int tx_servo(int sbc, int handle, int gpio, int pulseWidth, int servoFrequency, int servoOffset, int servoCycles)

    This starts software timed servo pulses on an output GPIO.
    I would only use software timed servo pulses for testing purposes. The timing jitter will cause the servo to fidget. This may cause it to overheat and wear out prematurely.
                handle: >= 0 (as returned by gpiochip_open)
                  gpio: the GPIO to be pulsed
            pulseWidth: pulse high time in microseconds (0=0ff, 500-2500)
        servoFrequency: the number of pulses per second (40-500)
           servoOffset: offset from nominal pulse start position
           servoCycles: the number of pulses to be sent, 0 for infinite
    If OK returns the number of entries left in the PWM queue for the GPIO.
    On failure returns a negative error code.
    Each successful call to this function consumes one PWM queue entry.
    Another servo command may be issued to the GPIO before the last has finished.
    If the last pulse had infinite cycles then it will be replaced by the new settings at the end of the current cycle. Otherwise it will be replaced by the new settings when all its cycles are complete.
    Multiple servo settings may be queued in this way.

int tx_wave(int sbc, int handle, int gpio, int count, lgPulse_p pulses)

    This starts a software timed wave on an output group.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
          gpio:  group leader.
         count: the number of pulses in the wave.
        pulses: the pulses.
    If OK returns the number of entries left in the wave queue for the group.
    On failure returns a negative error code.
    Each successful call to this function consumes one wave queue entry.
    This command starts a wave of pulses.
    pulses is an array of pulses to be transmitted on the group.
    Each pulse is defined by the following triplet:
    bits: the levels to set for the selected GPIO
    mask: the GPIO to select
    delay: the delay in microseconds before the next pulse
    Another wave command may be issued to the group before the last has finished transmission. The new wave will start when the previous wave has competed.
    Multiple waves may be queued in this way.

int tx_busy(int sbc, int handle, int gpio, int kind)

    This returns true if transmissions of the specified kind are active on the GPIO or group.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
          gpio: the GPIO or group to be tested.
          kind: LG_TX_PWM or LG_TX_WAVE.
    If OK returns 1 for busy and 0 for not busy.
    On failure returns a negative error code.

int tx_room(int sbc, int handle, int gpio, int kind)

    This returns the number of entries there are to queue further transmissions of the specified kind on a GPIO or GPIO group.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by gpiochip_open).
          gpio: the GPIO or group to be tested.
          kind: LG_TX_PWM or LG_TX_WAVE.
    If OK returns the number of free entries (0 for none).
    On failure returns a negative error code.

int gpio_set_debounce_time(int sbc, int handle, int gpio, int debounce_us)

    This sets the debounce time for a GPIO.
                sbc: >= 0 (as returned by rgpiod_start).
             handle: >= 0 (as returned by gpiochip_open).
               gpio: the GPIO to be configured.
        debounce_us: the debounce time in microseconds.
    If OK returns 0.
    On failure returns a negative error code.
    This only affects alerts.
    An alert will only be issued if the edge has been stable for at least debounce microseconds.
    Generally this is used to debounce mechanical switches (e.g. contact bounce).
    Suppose that a square wave at 5 Hz is being generated on a GPIO. Each edge will last 100000 microseconds. If a debounce time of 100001 is set no alerts will be generated, If a debounce time of 99999 is set 10 alerts will be generated per second.
    Note that level changes will be timestamped debounce microseconds after the actual level change.

int gpio_set_watchdog_time(int sbc, int handle, int gpio, int watchdog_us)

    This sets the watchdog time for a GPIO.
                sbc: >= 0 (as returned by rgpiod_start).
             handle: >= 0 (as returned by gpiochip_open).
               gpio: the GPIO to be configured.
        watchdog_us: the watchdog time in microseconds.
    If OK returns 0.
    On failure returns a negative error code.
    This only affects alerts.
    A watchdog alert will be sent if no edge alert has been issued for that GPIO in the previous watchdog microseconds.
    Note that only one watchdog alert will be sent per stream of edge alerts. The watchdog is reset by the sending of a new edge alert.
    The level is set to LG_TIMEOUT (2) for a watchdog alert.

int gpio_claim_alert(int sbc, int handle, int lFlags, int eFlags, int gpio, int nfyHandle)

    This claims a GPIO to be used as a source of alerts on level changes.
              sbc: >= 0 (as returned by rgpiod_start).
           handle: >= 0 (as returned by gpiochip_open).
             gpio: >= 0, as legal for the gpiochip.
           lFlags: line flags for the GPIO.
           eFlags: event flags for the GPIO.
        nfyHandle: >=0, a notification handle (use -1 for callbacks).
    If OK returns 0.
    On failure returns a negative error code.
    The line flags may be used to set the GPIO as active low, open drain, open source, pull up, pull down, pull off.
    The event flags are used to generate alerts for a rising edge, falling edge, or both edges.
    Use a notification handle of -1 unless you plan to read the alerts from a notification pipe you have opened.

int callback(int sbc, int handle, int gpio, int edge, CBFunc_t f, void *userdata)

    This function initialises a new callback.
             sbc: >= 0 (as returned by rgpiod_start).
          handle: >= 0,(as returned by gpiochip_open).
            gpio: >= 0, as legal for the gpiochip.
            edge: RISING_EDGE, FALLING_EDGE, or BOTH_EDGES.
               f: the callback function.
        userdata: a pointer to arbitrary user data.
    If OK returns a callback id.
    On failure returns a negative error code.
    The user supplied callback receives the chip, GPIO, edge, timestamp, and the userdata pointer, whenever the GPIO has the identified edge.
    The reported level will be one of
    0: change to low (a falling edge) 1: change to high (a rising edge) 2: no level change (a watchdog timeout)
    The timestamp is when the change happened reported as the number of nanoseconds since the epoch (start of 1970).
    If you want to track the level of more than one GPIO do so by maintaining the state in the callback. Do not use gpio_read. Remember the alert that triggered the callback may have happened several milliseconds before and the GPIO may have changed level many times since then.

int callback_cancel(int callback_id)

    This function cancels a callback identified by its id.
        callback_id: >= 0 (as returned by callback).
    If OK returns 0.
    On failure returns a negative error code.

int i2c_open(int sbc, int i2c_bus, int i2c_addr, int i2c_flags)

    This returns a handle for the device at address i2c_addr on bus i2c_bus.
    This is a privileged command. See permits.
              sbc: >= 0 (as returned by rgpiod_start).
          i2c_bus: >= 0.
         i2c_addr: 0-0x7F.
        i2c_flags: 0.
    If OK returns a handle (>= 0).
    On failure returns a negative error code.
    No flags are currently defined. This parameter should be set to zero.
    For the SMBus commands the low level transactions are shown at the end of the function description. The following abbreviations are used.
        S       (1 bit) : Start bit
        P       (1 bit) : Stop bit
        Rd/Wr   (1 bit) : Read/Write bit. Rd equals 1, Wr equals 0.
        A, NA   (1 bit) : Accept and not accept bit.
        Addr    (7 bits): I2C 7 bit address.
        i2c_reg (8 bits): A byte which often selects a register.
        Data    (8 bits): A data byte.
        Count   (8 bits): A byte defining the length of a block operation.
        [..]: Data sent by the device.

int i2c_close(int sbc, int handle)

    This closes the I2C device
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by i2c_open).
    If OK returns 0.
    On failure returns a negative error code.

int i2c_write_quick(int sbc, int handle, int bitVal)

    This sends a single bit (in the Rd/Wr bit) to the device.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by i2c_open).
        bitVal: 0-1, the value to write.
    If OK returns 0.
    On failure returns a negative error code.
    Quick command. SMBus 2.0 5.5.1
        S Addr bit [A] P

int i2c_write_byte(int sbc, int handle, int byteVal)

    This sends a single byte to the device.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        byteVal: 0-0xFF, the value to write.
    If OK returns 0.
    On failure returns a negative error code.
    Send byte. SMBus 2.0 5.5.2
        S Addr Wr [A] byteVal [A] P

int i2c_read_byte(int sbc, int handle)

    This reads a single byte from the device.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by i2c_open).
    If OK returns the byte read (0-255).
    On failure returns a negative error code.
    Receive byte. SMBus 2.0 5.5.3
        S Addr Rd [A] [Data] NA P

int i2c_write_byte_data(int sbc, int handle, int i2c_reg, int byteVal)

    This writes a single byte to the specified register of the device.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to write.
        byteVal: 0-0xFF, the value to write.
    If OK returns 0.
    On failure returns a negative error code.
    Write byte. SMBus 2.0 5.5.4
        S Addr Wr [A] i2c_reg [A] byteVal [A] P

int i2c_write_word_data(int sbc, int handle, int i2c_reg, int wordVal)

    This writes a single 16 bit word to the specified register of the device.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to write.
        wordVal: 0-0xFFFF, the value to write.
    If OK returns 0.
    On failure returns a negative error code.
    Write word. SMBus 2.0 5.5.4
        S Addr Wr [A] i2c_reg [A] wval_Low [A] wVal_High [A] P

int i2c_read_byte_data(int sbc, int handle, int i2c_reg)

    This reads a single byte from the specified register of the device.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to read.
    If OK returns the read byte (0-255).
    On failure returns a negative error code.
    Read byte. SMBus 2.0 5.5.5
        S Addr Wr [A] i2c_reg [A] S Addr Rd [A] [Data] NA P

int i2c_read_word_data(int sbc, int handle, int i2c_reg)

    This reads a single 16 bit word from the specified register of the device.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to read.
    If OK returns the read word (0-65535).
    On failure returns a negative error code.
    Read word. SMBus 2.0 5.5.5
        S Addr Wr [A] i2c_reg [A]
           S Addr Rd [A] [DataLow] A [DataHigh] NA P

int i2c_process_call(int sbc, int handle, int i2c_reg, int wordVal)

    This writes 16 bits of data to the specified register of the device and reads 16 bits of data in return.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to write/read.
        wordVal: 0-0xFFFF, the value to write.
    If OK returns the read word (0-65535).
    On failure returns a negative error code.
    Process call. SMBus 2.0 5.5.6
        S Addr Wr [A] i2c_reg [A] wVal_Low [A] wVal_High [A]
           S Addr Rd [A] [DataLow] A [DataHigh] NA P

int i2c_write_block_data(int sbc, int handle, int i2c_reg, const char *buf, int count)

    This writes up to 32 bytes to the specified register of the device.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to write.
            buf: an array with the data to send.
          count: 1-32, the number of bytes to write.
    If OK returns 0.
    On failure returns a negative error code.
    Block write. SMBus 2.0 5.5.7
        S Addr Wr [A] i2c_reg [A] count [A] buf0 [A] buf1 [A] ...
           [A] bufn [A] P

int i2c_read_block_data(int sbc, int handle, int i2c_reg, char *buf)

    This reads a block of up to 32 bytes from the specified register of the device.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to read.
            buf: an array to receive the read data.
    If OK returns the count of bytes read and updates buf.
    On failure returns a negative error code.
    The amount of returned data is set by the device.
    Block read. SMBus 2.0 5.5.7
        S Addr Wr [A] i2c_reg [A]
           S Addr Rd [A] [Count] A [buf0] A [buf1] A ... A [bufn] NA P

int i2c_block_process_call(int sbc, int handle, int i2c_reg, char *buf, int count)

    This writes data bytes to the specified register of the device and reads a device specified number of bytes of data in return.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to write/read.
            buf: an array with the data to send and to receive the read data.
          count: 1-32, the number of bytes to write.
    If OK returns the count of bytes read and updates buf.
    On failure returns a negative error code.
    The smbus 2.0 documentation states that a minimum of 1 byte may be sent and a minimum of 1 byte may be received. The total number of bytes sent/received must be 32 or less.
    Block write-block read. SMBus 2.0 5.5.8
        S Addr Wr [A] i2c_reg [A] count [A] buf0 [A] ...
           S Addr Rd [A] [Count] A [Data] ... A P

int i2c_read_i2c_block_data(int sbc, int handle, int i2c_reg, char *buf, int count)

    This reads count bytes from the specified register of the device. The count may be 1-32.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to read.
            buf: an array to receive the read data.
          count: 1-32, the number of bytes to read.
    If OK returns the count of bytes read and updates buf.
    On failure returns a negative error code.
        S Addr Wr [A] i2c_reg [A]
           S Addr Rd [A] [buf0] A [buf1] A ... A [bufn] NA P

int i2c_write_i2c_block_data(int sbc, int handle, int i2c_reg, const char *buf, int count)

    This writes 1 to 32 bytes to the specified register of the device.
            sbc: >= 0 (as returned by rgpiod_start).
         handle: >= 0 (as returned by i2c_open).
        i2c_reg: 0-255, the register to write.
            buf: the data to write.
          count: 1-32, the number of bytes to write.
    If OK returns 0.
    On failure returns a negative error code.
        S Addr Wr [A] i2c_reg [A] buf0 [A] buf1 [A] ... [A] bufn [A] P

int i2c_read_device(int sbc, int handle, char *buf, int count)

    This reads count bytes from the raw device into buf.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by i2c_open).
           buf: an array to receive the read data bytes.
         count: >0, the number of bytes to read.
    If OK returns the count of bytes read and updates buf.
    On failure returns a negative error code.
        S Addr Rd [A] [buf0] A [buf1] A ... A [bufn] NA P

int i2c_write_device(int sbc, int handle, const char *buf, int count)

    This writes count bytes from buf to the raw device.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by i2c_open).
           buf: an array containing the data bytes to write.
         count: >0, the number of bytes to write.
    If OK returns 0.
    On failure returns a negative error code.
        S Addr Wr [A] buf0 [A] buf1 [A] ... [A] bufn [A] P

int i2c_zip(int sbc, int handle, const char *inBuf, int inCount, char *outBuf, int outCount)

    This function executes a sequence of I2C operations. The operations to be performed are specified by the contents of inBuf which contains the concatenated command codes and associated data.
             sbc: >= 0 (as returned by rgpiod_start).
          handle: >= 0, as returned by a call to lgI2cOpen
           inBuf: pointer to the concatenated I2C commands, see below
         inCount: size of command buffer
          outBuf: pointer to buffer to hold returned data
        outCount: size of output buffer
    If OK returns the count of bytes read and updates outBuf.
    On failure returns a negative error code.
    The following command codes are supported:
    Name Cmd & Data Meaning
    End 0 No more commands
    Escape 1 Next P is two bytes
    On 2 Switch combined flag on
    Off 3 Switch combined flag off
    Address 4 P Set I2C address to P
    Flags 5 lsb msb Set I2C flags to lsb + (msb << 8)
    Read 6 P Read P bytes of data
    Write 7 P ... Write P bytes of data
    The address, read, and write commands take a parameter P. Normally P is one byte (0-255). If the command is preceded by the Escape command then P is two bytes (0-65535, least significant byte first).
    The address defaults to that associated with the handle. The flags default to 0. The address and flags maintain their previous value until updated.
    The returned I2C data is stored in consecutive locations of outBuf.
    Example
        Set address 0x53, write 0x32, read 6 bytes
        Set address 0x1E, write 0x03, read 6 bytes
        Set address 0x68, write 0x1B, read 8 bytes
        End
        0x04 0x53   0x07 0x01 0x32   0x06 0x06
        0x04 0x1E   0x07 0x01 0x03   0x06 0x06
        0x04 0x68   0x07 0x01 0x1B   0x06 0x08
        0x00

int notify_open(int sbc)

    Get a free notification handle.
    This is a privileged command. See permits.
        sbc: >= 0 (as returned by rgpiod_start).
    If OK returns a handle (>= 0).
    On failure returns a negative error code.
    A notification is a method for being notified of GPIO state changes via a pipe.
    Pipes are only accessible from the local machine so this function serves no purpose if you are using the library from a remote machine. The in-built (socket) notifications provided by callback should be used instead.
    The notification pipes are created in the library working directory.
    Notifications for handle x will be available at the pipe named .lgd-nfyx (where x is the handle number). E.g. if the function returns 15 then the notifications must be read from .lgd-nfy15.
    Each notification occupies 16 bytes in the fifo and has the following structure.
        typedef struct
        {
           uint64_t timestamp; // alert time in nanoseconds
           uint8_t chip;       // gpiochip device number
           uint8_t gpio;       // offset into gpio device
           uint8_t level;      // 0=low, 1=high, 2=timeout
           uint8_t flags;      // none currently defined
        } lgGpioReport_t;
    timestamp: the number of nanoseconds since the epoch (start of 1970) chip: the gpiochip device number (NOT the handle).
    gpio: the GPIO.
    level: indicates the level of the GPIO
    flags: no flags are currently defined
    For future proofing it is probably best to ignore any notification with non-zero flags.

int notify_resume(int sbc, int handle)

    Resume notifications on a handle.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by notify_open)
    If OK returns 0.
    On failure returns a negative error code.

int notify_pause(int sbc, int handle)

    Pauses notifications on a handle.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by notify_open)
    If OK returns 0.
    On failure returns a negative error code.
    Notifications for the handle are suspended until notify_resume is called.

int notify_close(int sbc, int handle)

    Stop notifications and releases the handle.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by notify_open)
    If OK returns 0.
    On failure returns a negative error code.

int script_store(int sbc, const char *script)

    This function stores a script for later execution.
    This is a privileged command. See permits.
    See scripts.html for details.
           sbc: >= 0 (as returned by rgpiod_start).
        script: the text of the script.
    If OK returns a handle (>=0).
    On failure returns a negative error code.

int script_run(int sbc, int handle, int count, const uint32_t *param)

    This function runs a stored script.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by script_store).
         count: 0-10, the number of parameters.
         param: an array of parameters.
    If OK returns 0.
    On failure returns a negative error code.
    param is an array of up to 10 parameters which may be referenced in the script as p0 to p9.

int script_update(int sbc, int handle, int count, const uint32_t *param)

    This function sets the parameters of a script. The script may or may not be running. The first numPar parameters of the script are overwritten with the new values.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by script_store).
         count: 0-10, the number of parameters.
         param: an array of parameters.
    If OK returns 0.
    On failure returns a negative error code.
    param is an array of up to 10 parameters which may be referenced in the script as p0 to p9.

int script_status(int sbc, int handle, uint32_t *param)

    This function returns the run status of a stored script as well as the current values of parameters 0 to 9.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by script_store).
         param: an array to hold the returned 10 parameters.
    If OK returns the script status and updates param.
    On failure returns a negative error code.
    The script status may be
        LG_SCRIPT_INITING
        LG_SCRIPT_READY
        LG_SCRIPT_RUNNING
        LG_SCRIPT_WAITING
        LG_SCRIPT_ENDED
        LG_SCRIPT_HALTED
        LG_SCRIPT_FAILED
    The current value of script parameters 0 to 9 are returned in param.

int script_stop(int sbc, int handle)

    This function stops a running script.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by script_store).
    If OK returns 0.
    On failure returns a negative error code.

int script_delete(int sbc, int handle)

    This function deletes a stored script.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by script_store).
    If OK returns 0.
    On failure returns a negative error code.

int serial_open(int sbc, const char *ser_tty, int ser_baud, int ser_flags)

    This function opens a serial device at a specified baud rate with specified flags. The device must be present in /dev.
    This is a privileged command. See permits.
              sbc: >= 0 (as returned by rgpiod_start).
          ser_tty: the serial device to open.
         ser_baud: the baud rate in bits per second, see below.
        ser_flags: 0.
    If OK returns 0.
    On failure returns a negative error code.
    The baud rate must be one of 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200, or 230400.
    No flags are currently defined. This parameter should be set to zero.

int serial_close(int sbc, int handle)

    This function closes the serial device.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by serial_open).
    If OK returns 0.
    On failure returns a negative error code.

int serial_write_byte(int sbc, int handle, int byteVal)

    This function writes byteVal to the serial port.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by serial_open).
    If OK returns 0.
    On failure returns a negative error code.

int serial_read_byte(int sbc, int handle)

    This function reads a byte from the serial port.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by serial_open).
    If OK returns the read byte (0-255).
    On failure returns a negative error code.

int serial_write(int sbc, int handle, const char *buf, int count)

    This function writes count bytes from buf to the the serial port.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by serial_open).
           buf: the array of bytes to write.
         count: the number of bytes to write.
    If OK returns 0.
    On failure returns a negative error code.

int serial_read(int sbc, int handle, char *buf, int count)

    This function reads up to count bytes from the the serial port and writes them to buf.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by serial_open).
           buf: an array to receive the read data.
         count: the maximum number of bytes to read.
    If OK returns the count of bytes read and updates buf.
    On failure returns a negative error code.
    If no data is ready zero is returned.

int serial_data_available(int sbc, int handle)

    Returns the number of bytes available to be read from the device.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by serial_open).
    If OK returns the count of bytes available.
    On failure returns a negative error code.

int shell(int sbc, const char *scriptName, const char *scriptString)

    This function uses the system call to execute a shell script with the given string as its parameter.
    This is a privileged command. See permits.
                 sbc: >= 0 (as returned by rgpiod_start).
          scriptName: the name of the script, only alphanumeric characters,
                      '-' and '_' are allowed in the name.
        scriptString: the string to pass to the script.
    If OK returns 0.
    On failure returns a negative error code.
    scriptName must exist in a directory named cgi in the daemon's configuration directory and must be executable.
    The returned exit status is normally 256 times that set by the shell script exit function. If the script can't be found 32512 will be returned.
    The following table gives some example returned statuses.
    Script exit status Returned system call status
    1 256
    5 1280
    10 2560
    200 51200
    script not found 32512
    Example
        // pass two parameters, hello and world
        status = shell_(sbc, "scr1", "hello world");
        // pass three parameters, hello, string with spaces, and world
        status = shell_(sbc, "scr1", "hello 'string with spaces' world");
        // pass one parameter, hello string with spaces world
        status = shell_(sbc, "scr1", "

int spi_open(int sbc, int spi_device, int spi_channel, int spi_baud, int spi_flags)

    This function returns a handle for the SPI device on the channel. Data will be transferred at baud bits per second. The flags may be used to modify the default behaviour.
    This is a privileged command. See permits.
                sbc: >= 0 (as returned by rgpiod_start).
         spi_device: >= 0
        spi_channel: >= 0
           spi_baud: SPI speed in bits per second.
          spi_flags: see below.
    If OK returns a handle (>= 0).
    On failure returns a negative error code.
    spi_flags consists of the least significant 2 bits.
        1  0
        m  m
    mm defines the SPI mode.
        Mode POL PHA
         0    0   0
         1    0   1
         2    1   0
         3    1   1
    The other bits in flags should be set to zero.

int spi_close(int sbc, int handle)

    This functions closes the SPI device identified by the handle.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by spi_open).
    If OK returns 0.
    On failure returns a negative error code.

int spi_read(int sbc, int handle, char *buf, int count)

    This function reads count bytes of data from the SPI device
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by spi_open).
           buf: an array to receive the read data bytes.
         count: the number of bytes to read.
    If OK returns the count of bytes read and updates buf.
    On failure returns a negative error code.

int spi_write(int sbc, int handle, const char *buf, int count)

    This function writes count bytes of data from buf to the SPI device
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by spi_open).
           buf: the data bytes to write.
         count: the number of bytes to write.
    If OK returns the count of bytes written.
    On failure returns a negative error code.

int spi_xfer(int sbc, int handle, const char *txBuf, char *rxBuf, int count)

    This function transfers count bytes of data from txBuf to the SPI device Simultaneously count bytes of data are read from the device and placed in rxBuf.
           sbc: >= 0 (as returned by rgpiod_start).
        handle: >= 0 (as returned by spi_open).
         txBuf: the data bytes to write.
         rxBuf: the received data bytes.
         count: the number of bytes to transfer.
    If OK returns the count of bytes transferred and updates rxBuf.
    On failure returns a negative error code.

pthread_t *thread_start(lgThreadFunc_t thread_func, void *userdata)

    Starts a new thread of execution with thread_func as the main routine.
        thread_func: the main function for the new thread.
           userdata: a pointer to an arbitrary argument.
    If OK returns a pointer to a pthread_t.
    On failure returns NULL.
    The function is passed the single argument userdata.
    The thread can be cancelled by passing the pointer to pthread_t to thread_stop.

void thread_stop(pthread_t *pth)

    Cancels the thread pointed at by pth.
        pth: the thread to be stopped.
    No value is returned.
    The thread to be stopped should have been started with thread_start.

int lgu_get_internal(int sbc, int config_id, uint64_t *config_value)

    Returns the value of a sbc configuration item.
    This is a privileged command. See permits.
                 sbc: >= 0 (as returned by rgpiod_start).
           config_id: the configuration item.
        config_value: pointer for returned value.
    If OK returns 0 and updates config_value.
    On failure returns a negative error code.

int lgu_set_internal(int sbc, int config_id, uint64_t config_value)

    Sets the value of a sbc configuration item.
    This is a privileged command. See permits.
                 sbc: >= 0 (as returned by rgpiod_start).
           config_id: the configuration item.
        config_value: the value to set.
    If OK returns 0.
    On failure returns a negative error code.

int lgu_get_sbc_name(int sbc, char *buf, int count)

    Return the lgd server name.
          sbc: >= 0 (as returned by rgpiod_start).
          buf: the server name is copied to this buffer.
        count: the maximum number of characters to copy.
    If OK returns the count of bytes copied and updates buf.
    On failure returns a negative error code.

int lgu_set_user(int sbc, const char *user, const char *secretsFile)

    Sets the rgpiod daemon user. The user then has the associated permissions.
                sbc: >= 0 (as returned by rgpiod_start).
               user: the user to set ("" defaults to the default user).
        secretsFile: the path to the shared secret file ("" defaults
                     to "~/.lg_secret").
    If OK returns 1 if the user was set, 0 otherwise.
    On failure returns a negative error code.
    Example
        if (lgu_set_user(sbc, "gpio", "")
        {
           printf("using user gpio permissions");
        }
        else
        {
           printf("using default permissions");
        }

int lgu_set_share_id(int sbc, int handle, int share_id)

    Sets the share id of an owned object.
             sbc: >= 0 (as returned by rgpiod_start).
          handle: >= 0
        share_id: >= 0, 0 stops sharing.
    If OK returns 0.
    On failure returns a negative error code.
    Normally objects associated with a handle are only accessible to the program which created them (and are automatically deleted when the program ends).
    If a non-zero share is set the object is accessible to any software which knows the share and the handle (and are not automatically deleted when the program ends).
    Example
        lgu_set_share_id(sbc, handle, 23);

int lgu_use_share_id(int sbc, int share_id)

    Sets the share id to be used when asking to use an object owned by another creator.
             sbc: >= 0 (as returned by rgpiod_start).
        share_id: >= 0, 0 stops sharing.
    If OK returns 0.
    On failure returns a negative error code.
    Normally objects associated with a handle are only accessible to the program which created them (and are automatically deleted when the program ends).
    If a non-zero share is set the object is accessible to any software which knows the share and the handle.
    Example
        lgu_use_share_id(sbc, 23);

uint32_t lgu_rgpio_version(void)

    Return the rgpio version.
    If OK returns the rgpio version.
    On failure returns a negative error code.

const char *lgu_error_text(int errnum)

    Return a text description for an error code.
        errnum: the error code.

void lgu_sleep(double sleepSecs)

    Delay execution for a given number of seconds.
        sleepSecs: the number of seconds to delay.

double lgu_time(void)

    Return the current time in seconds since the Epoch.

uint64_t lgu_timestamp(void)

    Return the current time in nanoseconds since the Epoch.

PARAMETERS

*addrStr
    A string specifying the host or IP address of the SBC running the rgpiod daemon. It may be NULL in which case localhost is used unless overridden by the LG_ADDR environment variable.

bitVal
    A value of 0 or 1.

*buf
    A buffer to hold data being sent or being received.

byteVal: 0-255
    An 8-bit byte value.

callback_id
    A value >= 0, as returned by a call to the callback.
    The id is passed to callback_cancel to cancel the callback.

CBFunc_t
        typedef void (*CBFunc_t)
           (int sbc, int chip, int gpio, int level, uint64_t timestamp, void * userdata);

char
    A single character, an 8 bit quantity able to store 0-255.

chipInfo
    A pointer to a lgChipInfo_t object.

config_id
    A number identifying a configuration item.
        LG_CFG_ID_DEBUG_LEVEL 0
        LG_CFG_ID_MIN_DELAY   1

config_value
    The value of a configuration item.

*config_value
    The value of a configuration item.

count
    The number of bytes to be transferred in a file, I2C, SPI, or serial command.

debounce_us
    The debounce time in microseconds.

double
    A floating point number.

edge
    Used to identify a GPIO level transition of interest. A rising edge is a level change from 0 to 1. A falling edge is a level change from 1 to 0.
        RISING_EDGE   1
        FALLING_EDGE  2
        BOTH_EDGES   3

eFlags
    The type of GPIO edge to generate an alert. See gpio_claim_alert.
        RISING_EDGE   1
        FALLING_EDGE  2
        BOTH_EDGES   3

errnum
    A negative number indicating a function call failed and the nature of the error.

f   A function.

*file
    A full file path. To be accessible the path must match an entry in the [files] section of the permits file.

float
    A floating point number.

*fpat
    A file path which may contain wildcards. To be accessible the path must match an entry in the [files] section of the permits file.

gpio
    A 0 based offset of a GPIO within a gpiochip.

gpioDev: >= 0
    The device number of a gpiochip.

*gpios
    An array of GPIO numbers.

groupBits
    A 64-bit value used to set the levels of a GPIO group.
    Set bit x to set GPIO x of the group high.
    Clear bit x to set GPIO x of the group low.

*groupBits
    A 64-bit value denoting the levels of a GPIO group.
    If bit x is set then GPIO x of the group is high.

groupMask
    A 64-bit value used to determine which members of a GPIO group should be updated.
    Set bit x to update GPIO x of the group.
    Clear bit x to leave GPIO x of the group unaltered.

handle: >= 0
    A number referencing an object opened by one of
    file_open
    gpiochip_open
    i2c_open
    notify_open
    serial_open script_store
    spi_open

i2c_addr: 0-0x7F
    The address of a device on the I2C bus.

i2c_bus: >= 0
    An I2C bus number.

i2c_flags: 0
    Flags which modify an I2C open command. None are currently defined.

i2c_reg: 0-255
    A register of an I2C device.

*inBuf
    A buffer used to pass data to a function.

inCount
    The size of an input buffer.

int A whole number, negative or positive.

int32_t
    A 32-bit signed value.

kind: LG_TX_PWM or LG_TX_WAVE
    A type of transmission: PWM or wave.

lFlags
    Line flags for the GPIO.
    The following values may be or'd to form the value.
        LG_SET_ACTIVE_LOW
        LG_SET_OPEN_DRAIN
        LG_SET_OPEN_SOURCE
        LG_SET_PULL_UP
        LG_SET_PULL_DOWN
        LG_SET_PULL_NONE

lgChipInfo_p
    A pointer to a lgChipInfo_t object.
        typedef struct lgChipInfo_s
        {
           uint32_t lines;                // number of GPIO
           char name[LG_GPIO_NAME_LEN];   // Linux name
           char label[LG_GPIO_LABEL_LEN]; // functional name
        } lgChipInfo_t, *lgChipInfo_p;

lgLineInfo_p
    A pointer to a lgLineInfo_t object.
        typedef struct lgLine_s
        {
           uint32_t offset;               // GPIO number
           uint32_t lFlags;
           char name[LG_GPIO_NAME_LEN];   // GPIO name
           char user[LG_GPIO_USER_LEN];   // user
        } lgLineInfo_t, *lgLineInfo_p;

lgPulse_p
    A pointer to a lgPulse_t object.
        typedef struct lgPulse_s
        {
           uint64_t bits;
           uint64_t mask;
           int64_t delay;
        } lgPulse_t, *lgPulse_p;

lgThreadFunc_t
        typedef void *(lgThreadFunc_t) (void *);

lineInfo
    A pointer to a lgLineInfo_t object.

mode
    A file open mode.
        LG_FILE_READ  1
        LG_FILE_WRITE 2
        LG_FILE_RW    3
    The following values can be or'd into the mode.
        LG_FILE_APPEND 4
        LG_FILE_CREATE 8
        LG_FILE_TRUNC  16

nfyHandle: >= 0
    This associates a notification with a GPIO alert.

*outBuf
    A buffer used to return data from a function.

outCount
    The size of an output buffer.

*param
    An array of script parameters.

*portStr
    A string specifying the port address used by the SBC running the rgpiod daemon. It may be NULL in which case "8889" is used unless overridden by the LG_PORT environment variable.

*pth
    A thread identifier, returned by thread_start.

pthread_t
    A thread identifier.

pulse_cycles: >= 0
    The number of pulses to generate. A value of 0 means infinite.#

pulse_off: >= 0
    The off period for a pulse in microseconds.

pulse_offset: >= 0
    The offset in microseconds from the nominal pulse start.

pulse_on: >= 0
    The on period for a pulse in microseconds.

pulses
    An pointer to an array of lgPulse_t objects.

pulseWidth: 0, 500-2500 microseconds
    Servo pulse width

pwmCycles: >= 0
    The number of PWM pulses to generate. A value of 0 means infinite.

pwmDutyCycle: 0-100 %
    PWM duty cycle %

pwmFrequency: 0.1-10000 Hz
    PWM frequency

pwmOffset: >= 0
    The offset in microseconds from the nominal PWM pulse start.

*rxBuf
    A pointer to a buffer to receive data.

sbc An integer defining a connected SBC. The value is returned by rgpiod_start upon success.

*script
    A pointer to the text of a script.

*scriptName
    The name of a shell_ script to be executed. The script must be present in the cgi directory of the daemon's configuration directory and must have execute permission.

*scriptString
    The string to be passed to a shell_ script to be executed.

*secretsFile
    The file containing the shared secret for a user. If the shared secret for a user matches that known by the rgpiod daemon the user can "log in" to the daemon.

seekFrom
        LG_FROM_START   0
        LG_FROM_CURRENT 1
        LG_FROM_END     2

seekOffset
    The number of bytes to move forward (positive) or backwards (negative) from the seek position (start, current, or end of file).

ser_baud
    The speed of serial communication in bits per second.

ser_flags
    Flags which modify a serial open command. None are currently defined.

*ser_tty
    The name of a serial tty device, e.g. /dev/ttyAMA0, /dev/ttyUSB0, /dev/tty1.

servoCycles: >= 0
    The number of servo pulses to generate. A value of 0 means infinite.

servoFrequency: 40-500 Hz
    Servo pulse frequency

servoOffset: >= 0
    The offset in microseconds from the nominal servo pulse start.

share_id
    Objects created with a non-zero share_id are persistent and may be used by other software which knows the share_id.

sleepSecs
    The number of seconds to delay.

spi_baud
    The speed of SPI communication in bits per second.

spi_channel: >= 0
    A SPI channel.

spi_device: >= 0
    A SPI device.

spi_flags
    See spi_open and bb_spi_open.

thread_func
    A function of type gpioThreadFunc_t used as the main function of a thread.

*txBuf
    An array of bytes to transmit.

uint32_t
    A 32-bit unsigned value.

uint64_t
    A 64-bit unsigned value.

*user
    A name known by the rgpiod daemon and associated with a set of user permissions.

*userdata
    A pointer to arbitrary user data. This may be used to identify the instance.
    You must ensure that the pointer is in scope at the time it is processed. If it is a pointer to a global this is automatic. Do not pass the address of a local variable. If you want to pass a transient object then use the following technique.
    In the calling function:
        user_type *userdata;
        user_type my_userdata;
        userdata = malloc(sizeof(user_type));
        *userdata = my_userdata;
    In the receiving function:
        user_type my_userdata = *(user_type*)userdata;
        free(userdata);

value: 0-1
    A GPIO level.

*values
    An array of GPIO values.

void
    Denoting no parameter is required

watchdog_us
    The watchdog time in microseconds.

wordVal: 0-65535
    A 16-bit word value.

rgpio Error Codes
    typedef enum
    {
       lgif_bad_send           = -2000,
       lgif_bad_recv           = -2001,
       lgif_bad_getaddrinfo    = -2002,
       lgif_bad_connect        = -2003,
       lgif_bad_socket         = -2004,
       lgif_bad_noib           = -2005,
       lgif_duplicate_callback = -2006,
       lgif_bad_malloc         = -2007,
       lgif_bad_callback       = -2008,
       lgif_notify_failed      = -2009,
       lgif_callback_not_found = -2010,
       lgif_unconnected_sbc    = -2011,
       lgif_too_many_pis       = -2012,
    } lgifError_t;

SEE ALSO
rgpiod(1), rgs(1), lgpio(3)