lgpio(3)

NAME
lgpio - A C library to manipulate a local SBC's GPIO.

SYNOPSIS
#include <lgpio.h> gcc -Wall -o prog prog.c -llgpio ./prog

DESCRIPTION
lgpio is a C library for Linux Single Board Computers which allows control of the General Purpose Input Output pins.

  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 a simple interface to start and stop new threads

  Usage
Include <lgpio.h> in your source files.
Assuming your source is in a single file called prog.c use the following command to build and run the executable.
    gcc -Wall -o prog prog.c -llgpio
For examples of usage see the C programs within the lg archive file.

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

OVERVIEW

  GPIO
lgGpiochipOpen Opens a gpiochip device
lgGpiochipClose Closes a gpiochip device
lgGpioGetChipInfo Gets gpiochip information
lgGpioGetLineInfo Gets gpiochip line information
lgGpioGetMode Gets the mode of a GPIO
lgGpioSetUser Notifies Linux of the GPIO user
lgGpioClaimInput Claims a GPIO for input
lgGpioClaimOutput Claims a GPIO for output
lgGpioClaimAlert Claims a GPIO for alerts
lgGpioFree Frees a GPIO
lgGroupClaimInput Claims a group of GPIO for inputs
lgGroupClaimOutput Claims a group of GPIO for outputs
lgGroupFree Frees a group of GPIO
lgGpioRead Reads a GPIO
lgGpioWrite Writes a GPIO
lgGroupRead Reads a group of GPIO
lgGroupWrite Writes a group of GPIO
lgTxPulse Starts pulses on a GPIO
lgTxPwm Starts PWM pulses on a GPIO
lgTxServo Starts Servo pulses on a GPIO
lgTxWave Starts a wave on a group of GPIO
lgTxBusy See if tx is active on a GPIO or group
lgTxRoom See if more room for tx on a GPIO or group
lgGpioSetDebounce Sets the debounce time for a GPIO
lgGpioSetWatchdog Sets the watchdog time for a GPIO
lgGpioSetAlertsFunc Starts a GPIO callback
lgGpioSetSamplesFunc Starts a GPIO callback for all GPIO

  I2C
lgI2cOpen Opens an I2C device
lgI2cClose Closes an I2C device
lgI2cWriteQuick SMBus write quick
lgI2cReadByte SMBus read byte
lgI2cWriteByte SMBus write byte
lgI2cReadByteData SMBus read byte data
lgI2cWriteByteData SMBus write byte data
lgI2cReadWordData SMBus read word data
lgI2cWriteWordData SMBus write word data
lgI2cReadBlockData SMBus read block data
lgI2cWriteBlockData SMBus write block data
lgI2cReadI2CBlockData SMBus read I2C block data
lgI2cWriteI2CBlockData SMBus write I2C block data
lgI2cReadDevice Reads the raw I2C device
lgI2cWriteDevice Writes the raw I2C device
lgI2cProcessCall SMBus process call
lgI2cBlockProcessCall SMBus block process call
lgI2cSegments Performs multiple I2C transactions
lgI2cZip Performs multiple I2C transactions

  NOTIFICATIONS
lgNotifyOpen Request a notification
lgNotifyClose Close a notification
lgNotifyPause Pause notifications
lgNotifyResume Start notifications

  SERIAL
lgSerialOpen Opens a serial device
lgSerialClose Closes a serial device
lgSerialReadByte Reads a byte from a serial device
lgSerialWriteByte Writes a byte to a serial device
lgSerialRead Reads bytes from a serial device
lgSerialWrite Writes bytes to a serial device
lgSerialDataAvailable Returns number of bytes ready to be read

  SPI
lgSpiOpen Opens a SPI device
lgSpiClose Closes a SPI device
lgSpiRead Reads bytes from a SPI device
lgSpiWrite Writes bytes to a SPI device
lgSpiXfer Transfers bytes with a SPI device

  THREADS
lgThreadStart Start a new thread
lgThreadStop Stop a previously started thread

  UTILITIES
lguVersion Gets the library version
lguSbcName Gets the host name of the SBC
lguGetInternal Get an internal configuration value
lguSetInternal Set an internal configuration value
lguSleep Sleeps for a given time
lguTimestamp Gets the current timestamp
lguTime Gets the current time
lguErrorText Gets a text description of an error code
lguSetWorkDir Set the working directory
lguGetWorkDir Get the working directory

FUNCTIONS

int lgGpiochipOpen(int gpioDev)

    This returns a handle to a gpiochip device.
        gpioDev: >= 0
    If OK returns a handle (>= 0).
    On failure returns a negative error code.
    Example
        h = lgGpiochipOpen(0); // open /dev/gpiochip0
        if (h >= 0)
        {
           // open ok
        }
        else
        {
           // open error
        }

int lgGpiochipClose(int handle)

    This closes an opened gpiochip device.
        handle: >= 0 (as returned by lgGpiochipOpen)
    If OK returns 0.
    On failure returns a negative error code.
    Example
        status = lgGpiochipClose(h); // close gpiochip
        if (status < 0)
        {
           // close failed
        }

int lgGpioGetChipInfo(int handle, lgChipInfo_p chipInfo)

    This returns information about a gpiochip.
          handle: >= 0 (as returned by lgGpiochipOpen)
        chipInfo: A pointer to space for a lgChipInfo_t object
    If OK returns 0 and updates chipInfo.
    On failure returns a negative error code.
    This command gets the number of GPIO on the gpiochip, its name, and its usage.
    Example
        lgChipInfo_t cInfo;
        status = lgGpioGetChipInfo(h, &cInfo);
        if (status == LG_OKAY)
        {
           printf("lines=%d name=%s label=%s,
              cInfo.lines, cInfo.name, cInfo.label))
        }

int lgGpioGetLineInfo(int handle, int gpio, lgLineInfo_p lineInfo)

    Returns information about a GPIO.
          handle: >= 0 (as returned by lgGpiochipOpen)
            gpio: >= 0, as legal for the gpiochip
        lineInfo: A pointer to space for a lgLineInfo_t object
    If OK returns 0 and updates lineInfo.
    On failure returns a negative error code.
    This command gets information for a GPIO of a gpiochip. In particular it gets the GPIO number, flags, its user, and its purpose.
    The meaning of the flags bits are as given for the mode by lgGpioGetMode.
    The user and purpose fields are filled in by the software which has claimed the GPIO and may be blank.
    Example
        lgLineInfo_t lInfo;
        status = lgGpioGetLineInfo(h, gpio, &lInfo);
        if (status == LG_OKAY)
        {
           printf("lFlags=%d name=%s user=%s,
              lInfo.lFlags, lInfo.name, lInfo.user))
        }

int lgGpioGetMode(int handle, int gpio)

    Returns the GPIO mode.
          handle: >= 0 (as returned by lgGpiochipOpen)
            gpio: >= 0, as legal for the gpiochip
    If OK returns the GPIO mode.
    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 lgGpioSetUser(int handle, const char *gpiouser)

    This sets the user string to be associated with each claimed GPIO.
          handle: >= 0 (as returned by lgGpiochipOpen)
        gpiouser: a string up to 32 characters long
    If OK returns 0.
    On failure returns a negative error code.
    Example
        status = lgGpioSetUser(h, "my_title");

int lgGpioClaimInput(int handle, int lFlags, int gpio)

    This claims a GPIO for input.
        handle: >= 0 (as returned by lgGpiochipOpen)
        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, or open source.
    Example
        // open GPIO 23 for input
        status = lgGpioClaimInput(h, 0, 23);

int lgGpioClaimOutput(int handle, int lFlags, int gpio, int level)

    This claims a GPIO for output.
        handle: >= 0 (as returned by lgGpiochipOpen)
        lFlags: line flags for the GPIO
          gpio: the GPIO to be claimed
         level: the initial level to set 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, or open source.
    If level is zero the GPIO will be initialised low. If any other value is used the GPIO will be initialised high.
    Example
        // open GPIO 31 for high output
        status = lgGpioClaimOutput(h, 0, 31, 1);

int lgGpioClaimAlert(int handle, int lFlags, int eFlags, int gpio, int nfyHandle)

    This claims a GPIO for alerts on level changes.
           handle: >= 0 (as returned by lgGpiochipOpen)
           lFlags: line flags for the GPIO
           eFlags: event flags for the GPIO
             gpio: >= 0, as legal for the gpiochip
        nfyHandle: >= 0 (as returned by lgNotifyOpen)
    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, or open source.
    The event flags are used to specify alerts for a rising edge, falling edge, or both edges.
    The alerts will be sent to a previously opened notification. If you don't want them sent to a notification set nfyHandle to -1.
    The alerts will also be sent to any callback registered for the GPIO by lgGpioSetAlertsFunc.
    All GPIO alerts are also sent to a callback registered by lgGpioSetSamplesFunc.
    Example
        status = lgGpioClaimAlert(h, 0, LG_BOTH_EDGES, 16, -1);

int lgGpioFree(int handle, int gpio)

    This frees a GPIO.
        handle: >= 0 (as returned by lgGpiochipOpen)
          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.
    Example
        status = lgGpioFree(h, 16);

int lgGroupClaimInput(int handle, int lFlags, int count, const int *gpios)

    This claims a group of GPIO for inputs.
        handle: >= 0 (as returned by lgGpiochipOpen)
        lFlags: line flags for the GPIO group
         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, or open source.
    gpios is an array of one or more GPIO. The first GPIO is called the group leader and is used to reference the group as a whole.
    Example
        int buttons[4] = {9, 7, 2, 6};
        status = lgGroupClaimInput(h, 0, 4, buttons);
        if (status == LG_OKAY)
        {
           // OK
        }
        else
        {
           // Error
        }

int lgGroupClaimOutput(int handle, int lFlags, int count, const int *gpios, const int *levels)

    This claims a group of GPIO for outputs.
        handle: >= 0 (as returned by lgGpiochipOpen)
        lFlags: line flags for the GPIO group
         count: the number of GPIO to claim
         gpios: the group GPIO
        levels: the initial level 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, or open source.
    gpios is an array of one or more GPIO. The first GPIO is called the group leader and is used to reference the group as a whole.
    levels is an array of initialisation values for the GPIO. If a value is zero the corresponding GPIO will be initialised low. If any other value is used the corresponding GPIO will be initialised high.
    Example
        int leds[7] =   {15, 16, 17, 8, 12, 13, 14};
        int levels[7] = { 1,  0,  1, 1,  1,  0,  0};
        status = lgGroupClaimInput(h, 0, 7, leds, levels);
        if (status == LG_OKAY)
        {
           // OK
        }
        else
        {
           // Error
        }

int lgGroupFree(int handle, int gpio)

    This frees all the GPIO associated with a group.
        handle: >= 0 (as returned by lgGpiochipOpen)
          gpio: the group 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.
    Example
        status = lgGroupFree(9); // free buttons

int lgGpioRead(int handle, int gpio)

    This returns the level of a GPIO.
        handle: >= 0 (as returned by lgGpiochipOpen)
          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.
    Example
        level = lgGpioRead(h, 15); // get level of GPIO 15

int lgGpioWrite(int handle, int gpio, int level)

    This sets the level of an output GPIO.
        handle: >= 0 (as returned by lgGpiochipOpen)
          gpio: the GPIO to be written
         level: the level to set
    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).
    Example
        status = lgGpioWrite(h, 23, 1); // set GPIO 23 high

int lgGroupRead(int handle, int gpio, uint64_t *groupBits)

    This returns the levels read from a group.
           handle: >= 0 (as returned by lgGpiochipOpen)
             gpio: the group to be read
        groupBits: a pointer to a 64-bit memory area for the returned levels
    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.
    Example
        // assuming a read group of 4 buttons: 9, 7, 2, 6.
        uint64_t bits;
        size = lgGroupRead(h, 9, &bits); // 9 is buttons group leader
        if (size >= 0) // size of group is returned so size will be 4
        {
           level_9 = (bits >> 0) & 1;
           level_7 = (bits >> 1) & 1;
           level_2 = (bits >> 2) & 1;
           level_6 = (bits >> 3) & 1;
        }
        else
        {
           // error
        }

int lgGroupWrite(int handle, int gpio, uint64_t groupBits, uint64_t groupMask)

    This sets the levels of an output group.
           handle: >= 0 (as returned by lgGpiochipOpen)
             gpio: the 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 groupBits.
    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 modified by the groupMask. A GPIO is only updated if the corresponding bit in the mask is 1.
    Example
        // assuming an output group of 7 LEDs: 15, 16, 17, 8, 12, 13, 14.
        // switch on all LEDs
        status = lgGroupWrite(h, 15, 0x7f, 0x7f);
        // switch off all LEDs
        status = lgGroupWrite(h, 15, 0x00, 0x7f);
        // switch on first 4 LEDs, leave others unaltered
        status = lgGroupWrite(h, 15, 0x0f, 0x0f);
        // switch on LED attached to GPIO 13, leave others unaltered
        status = lgGroupWrite(h, 15, 32, 32);

int lgTxPulse(int handle, int gpio, int pulseOn, int pulseOff, int pulseOffset, int pulseCycles)

    This starts software timed pulses on an output GPIO.
             handle: >= 0 (as returned by lgGpiochipOpen)
               gpio: the GPIO to be written
            pulseOn: pulse high time in microseconds
           pulseOff: pulse low time in microseconds
        pulseOffset: offset from nominal pulse start position
        pulseCycles: 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 pulseOn and pulseOff 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.
    pulseCycles cycles are transmitted (0 means infinite). Each cycle consists of pulseOn microseconds of GPIO high followed by pulseOff 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 / (pulseOn + pulseOff) Hz.
    The set duty cycle will be pulseOn / (pulseOn + pulseOff) * 100 %.
    E.g. if pulseOn is 50 and pulseOff is 100 the frequency will be 6666.67 Hz and the duty cycle will be 33.33 %.
    pulseOffset is a microsecond offset from the natural start of the PWM 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.
    Example
        slots_left = lgTxPulse(h,  8, 100000, 100000, 0, 0); // flash LED at 5 Hz
        slots_left = lgTxPulse(h, 30, 1500, 18500, 0, 0); // move servo to centre
        slots_left = lgTxPulse(h, 30, 2000, 18000, 0, 0); // move servo clockwise

int lgTxPwm(int handle, int gpio, float pwmFrequency, float pwmDutyCycle, int pwmOffset, int pwmCycles)

    This starts software timed PWM on an output GPIO.
              handle: >= 0 (as returned by lgGpiochipOpen)
                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 complete.
    Multiple PWM settings may be queued in this way.

int lgTxServo(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 lgGpiochipOpen)
                  gpio: the GPIO to be pulsed
            pulseWidth: pulse high time in microseconds (0=off, 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 compete.
    Multiple servo settings may be queued in this way.

int lgTxWave(int handle, int gpio, int count, lgPulse_p pulses)

    This starts a wave on an output group of GPIO.
        handle: >= 0 (as returned by lgGpiochipOpen)
          gpio: the 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 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.
    Example
        #include <stdio.h>
        #include <lgpio.h>
        #define PULSES 2000
        int main(int argc, char *argv[])
        {
           int GPIO[] =   {16, 17, 18, 19, 20, 21};
           int levels[] = { 1,  1,  1,  1,  1,  1};
           int h;
           int e;
           int mask;
           int delay;
           int p;
           lgPulse_t pulses[PULSES];
           h = lgGpiochipOpen(0); // open /dev/gpiochip0
           if (h < 0) { printf("ERROR: %s (%d), lguErrorText(h), h); return 1; }
           e =  lgGroupClaimOutput(h, 0, 6, GPIO, levels);
           if (e < 0) { printf("ERROR: %s (%d), lguErrorText(e), e); return 1; }
           mask = 0;
           p = 0;
           for (p=0; p<PULSES; p++)
           {
              pulses[p].bits = (p+1)>>2;  // see what sort of pattern we get
              pulses[p].mask = mask;      // with bits and mask changing
              pulses[p].delay = (PULSES + 500) - p;
              if (++mask > 0x3f) mask = 0;
           }
           lgTxWave(h, GPIO[0], p, pulses);
           while (lgTxBusy(h, GPIO[0], LG_TX_WAVE)) lguSleep(0.1);
           lgGpiochipClose(h);
        }

int lgTxBusy(int handle, int gpio, int kind)

    This returns true if transmissions of the specified kind are active on the GPIO or group.
        handle: >= 0 (as returned by lgGpiochipOpen)
          gpio: the gpio or group to be checked
          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.
    Example
        while (lgTxBusy(h, 15, LG_TX_PWM)) // wait for PWM to finish on GPIO 15
           lguSleep(0.1);

int lgTxRoom(int handle, int gpio, int kind)

    This returns the number of entries available for queueing transmissions of the specified kind on the GPIO or group.
        handle: >= 0 (as returned by lgGpiochipOpen)
          gpio: the gpio or group to be checked
          kind: LG_TX_PWM or LG_TX_WAVE
    If OK returns the number of free entries (0 if none).
    On failure returns a negative error code.
    Example
        while (lgTxRoom(h, 17, LG_TX_WAVE) > 0))
        {
           // queue another wave
        }

int lgGpioSetDebounce(int handle, int gpio, int debounce_us)

    This sets the debounce time for a GPIO.
             handle: >= 0 (as returned by lgGpiochipOpen)
               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.
    Example
        lgSetDebounceTime(h, 16, 1000); // set a millisecond of debounce

int lgGpioSetWatchdog(int handle, int gpio, int watchdog_us)

    This sets the watchdog time for a GPIO.
             handle: >= 0 (as returned by lgGpiochipOpen)
               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.
    Example
        lgSetWatchdogTime(h, 17, 200000); // alert if nothing for 0.2 seconds

int lgGpioSetAlertsFunc(int handle, int gpio, lgGpioAlertsFunc_t cbf, void *userdata)

    This sets up a callback to be called when an alert GPIO changes state.
          handle: >= 0 (as returned by lgGpiochipOpen)
            gpio: the GPIO to be monitored
             cbf: the callback function
        userdata: a pointer to arbitrary user data
    If OK returns 0.
    On failure returns a negative error code.
    Example
        #include <stdio.h>
        #include <inttypes.h>
        #include <lgpio.h>
        void afunc(int e, lgGpioAlert_p evt, void *data)
        {
           int i;
           int userdata = *(int*)data;
           for (i=0; i<e; i++)
           {
              printf("u=%d t=%"PRIu64" c=%d g=%d l=%d f=%d (%d of %d),
                 userdata, evt[i].report.timestamp, evt[i].report.chip,
                 evt[i].report.gpio, evt[i].report.level,
                 evt[i].report.flags, i+1, e);
           }
        }
        int main(int argc, char *argv[])
        {
           int h;
           int e;
           static int userdata=123;
           h = lgGpiochipOpen(0);
           if (h < 0) { printf("ERROR: %s (%d), lguErrorText(h), h); return 1; }
           lgGpioSetAlertsFunc(h, GPIO, afunc, &userdata);
           e = lgGpioClaimAlert(h, 0, LG_BOTH_EDGES, 23, -1);
           if (e < 0) { printf("ERROR: %s (%d), lguErrorText(e), e); return 1; }
           lguSleep(10);
           lgGpiochipClose(h);
        }
    Assuming square wave at 800 Hz is being received at GPIO 23.
        u=123 ts=1602089980691229623 c=0 g=23 l=1 f=0 (1 of 1)
        u=123 ts=1602089980691854934 c=0 g=23 l=0 f=0 (1 of 1)
        u=123 ts=1602089980692479308 c=0 g=23 l=1 f=0 (1 of 1)
        u=123 ts=1602089980693114566 c=0 g=23 l=0 f=0 (1 of 1)
        u=123 ts=1602089980693728784 c=0 g=23 l=1 f=0 (1 of 1)
        u=123 ts=1602089980694354355 c=0 g=23 l=0 f=0 (1 of 1)
        u=123 ts=1602089980694978468 c=0 g=23 l=1 f=0 (1 of 1)

void lgGpioSetSamplesFunc(lgGpioAlertsFunc_t cbf, void *userdata)

    This sets up a callback to be called when any alert GPIO changes state.
             cbf: the callback function
        userdata: a pointer to arbitrary user data
    If OK returns 0.
    On failure returns a negative error code.
    Note that no handle or gpio is specified. The callback function will receive alerts for all gpiochips and gpio.
    Example
        #include <stdio.h>
        #include <inttypes.h>
        #include <lgpio.h>
        void afunc(int e, lgGpioAlert_p evt, void *data)
        {
           int i;
           int userdata = *(int*)data;
           for (i=0; i<e; i++)
           {
              printf("u=%d t=%"PRIu64" c=%d g=%d l=%d f=%d (%d of %d),
                 userdata, evt[i].report.timestamp, evt[i].report.chip,
                 evt[i].report.gpio, evt[i].report.level,
                 evt[i].report.flags, i+1, e);
           }
        }
        int main(int argc, char *argv[])
        {
           int h;
           static int userdata=456;
           h = lgGpiochipOpen(0);
           if (h < 0) { printf("ERROR: %s (%d), lguErrorText(h), h); return 1; }
           lgGpioSetSamplesFunc(afunc, &userdata);
           lgGpioClaimAlert(h, 0, LG_BOTH_EDGES, 23, -1);
           lgGpioClaimAlert(h, 0, LG_BOTH_EDGES, 24, -1);
           lgGpioClaimAlert(h, 0, LG_BOTH_EDGES, 25, -1);
           lguSleep(10);
           lgGpiochipClose(h);
        }
    Assuming square wave at 800 Hz is being received at GPIO 23, 24, 25.
        u=456 ts=1602090898869011679 c=0 g=24 l=1 f=0 (1 of 3)
        u=456 ts=1602090898869016627 c=0 g=25 l=1 f=0 (2 of 3)
        u=456 ts=1602090898869627667 c=0 g=23 l=0 f=0 (3 of 3)
        u=456 ts=1602090898869636522 c=0 g=24 l=0 f=0 (1 of 3)
        u=456 ts=1602090898869641157 c=0 g=25 l=0 f=0 (2 of 3)
        u=456 ts=1602090898870252614 c=0 g=23 l=1 f=0 (3 of 3)
        u=456 ts=1602090898870261155 c=0 g=24 l=1 f=0 (1 of 3)
        u=456 ts=1602090898870266208 c=0 g=25 l=1 f=0 (2 of 3)
        u=456 ts=1602090898870879800 c=0 g=23 l=0 f=0 (3 of 3)
        u=456 ts=1602090898870890477 c=0 g=24 l=0 f=0 (1 of 3)
        u=456 ts=1602090898870895529 c=0 g=25 l=0 f=0 (2 of 3)
        u=456 ts=1602090898871503652 c=0 g=23 l=1 f=0 (3 of 3)

int lgNotifyOpen(void)

    This function requests a free notification.
    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 or socket.
    The notification pipes are created in the library working directory (see lguGetWorkDir).
    Pipe notifications for handle x will be available at the pipe named .lgd-nfy* (where * is the handle number). E.g. if the function returns 15 then the notifications must be read from .lgd-nfy15.
    Socket notifications are returned to the socket which requested the handle.
    Example
        h = lgNotifyOpen();
        if (h >= 0)
        {
           sprintf(str, ".lgd-nfy%d", h);
           fd = open(str, O_RDONLY);
           if (fd >= 0)
           {
              // Okay.
           }
           else
           {
              // Error.
           }
        }
        else
        {
           // Error.
        }

int lgNotifyResume(int handle)

    This function restarts notifications on a paused notification.
        handle: >= 0 (as returned by lgNotifyOpen)
    If OK returns 0.
    On failure returns a negative error code.
    The notification gets state changes for each associated GPIO.
    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) 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.
    Example
        // Start notifications for associated GPIO.
        lgNotifyResume(h);

int lgNotifyPause(int handle)

    This function pauses notifications.
        handle: >= 0 (as returned by lgNotifyOpen)
    If OK returns 0.
    On failure returns a negative error code.
    Notifications are suspended until lgNotifyResume is called.
    Example
        lgNotifyPause(h);

int lgNotifyClose(int handle)

    This function stops notifications and frees the handle for reuse.
        handle: >= 0 (as returned by lgNotifyOpen)
    If OK returns 0.
    On failure returns a negative error code.
    Example
        lgNotifyClose(h);

int lgI2cOpen(int i2cDev, int i2cAddr, int i2cFlags)

    This returns a handle for the device at the address on the I2C bus.
          i2cDev: >= 0
         i2cAddr: 0-0x7F
        i2cFlags: 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
        i2cReg (8 bits): Command byte, 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 lgI2cClose(int handle)

    This closes the I2C device.
        handle: >= 0 (as returned by lgI2cOpen)
    If OK returns 0.
    On failure returns a negative error code.

int lgI2cWriteQuick(int handle, int bitVal)

    This sends a single bit (in the Rd/Wr bit) to the device.
        handle: >= 0 (as returned by lgI2cOpen)
        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 lgI2cWriteByte(int handle, int byteVal)

    This sends a single byte to the device.
         handle: >= 0 (as returned by lgI2cOpen)
        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] bVal [A] P

int lgI2cReadByte(int handle)

    This reads a single byte from the device.
        handle: >= 0 (as returned by lgI2cOpen)
    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 lgI2cWriteByteData(int handle, int i2cReg, int byteVal)

    This writes a single byte to the specified register of the device.
         handle: >= 0 (as returned by lgI2cOpen)
         i2cReg: 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] i2cReg [A] bVal [A] P

int lgI2cWriteWordData(int handle, int i2cReg, int wordVal)

    This writes a single 16 bit word to the specified register of the device.
         handle: >= 0 (as returned by lgI2cOpen)
         i2cReg: 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] i2cReg [A] wValLow [A] wValHigh [A] P

int lgI2cReadByteData(int handle, int i2cReg)

    This reads a single byte from the specified register of the device.
        handle: >= 0 (as returned by lgI2cOpen)
        i2cReg: 0-255, the register to read
    If OK returns the byte read (0-255).
    On failure returns a negative error code.
    Read byte. SMBus 2.0 5.5.5
        S Addr Wr [A] i2cReg [A] S Addr Rd [A] [Data] NA P

int lgI2cReadWordData(int handle, int i2cReg)

    This reads a single 16 bit word from the specified register of the device.
        handle: >= 0 (as returned by lgI2cOpen)
        i2cReg: 0-255, the register to read
    If OK returns the word read (0-65535).
    On failure returns a negative error code.
    Read word. SMBus 2.0 5.5.5
        S Addr Wr [A] i2cReg [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P

int lgI2cProcessCall(int handle, int i2cReg, int wordVal)

    This writes 16 bits of data to the specified register of the device and reads 16 bits of data in return.
         handle: >= 0 (as returned by lgI2cOpen)
         i2cReg: 0-255, the register to write/read
        wordVal: 0-0xFFFF, the value to write
    If OK returns the word read (0-65535).
    On failure returns a negative error code.
    Process call. SMBus 2.0 5.5.6
        S Addr Wr [A] i2cReg [A] wValLow [A] wValHigh [A]
           S Addr Rd [A] [DataLow] A [DataHigh] NA P

int lgI2cWriteBlockData(int handle, int i2cReg, const char *txBuf, int count)

    This writes up to 32 bytes to the specified register of the device.
        handle: >= 0 (as returned by lgI2cOpen)
        i2cReg: 0-255, the register to write
         txBuf: 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] i2cReg [A] count [A]
           txBuf0 [A] txBuf1 [A] ... [A] txBufn [A] P

int lgI2cReadBlockData(int handle, int i2cReg, char *rxBuf)

    This reads a block of up to 32 bytes from the specified register of the device.
        handle: >= 0 (as returned by lgI2cOpen)
        i2cReg: 0-255, the register to read
         rxBuf: an array to receive the read data
    The amount of returned data is set by the device.
    If OK returns the count of bytes read (0-32) and updates rxBuf.
    On failure returns a negative error code.
    Block read. SMBus 2.0 5.5.7
        S Addr Wr [A] i2cReg [A]
           S Addr Rd [A] [Count] A [rxBuf0] A [rxBuf1] A ... A [rxBufn] NA P

int lgI2cBlockProcessCall(int handle, int i2cReg, char *ioBuf, 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.
        handle: >= 0 (as returned by lgI2cOpen)
        i2cReg: 0-255, the register to write/read
         ioBuf: 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 (0-32) and updates ioBuf.
    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] i2cReg [A] count [A] ioBuf0 [A] ... ioBufn [A]
           S Addr Rd [A] [Count] A [ioBuf0] A ... [ioBufn] A P

int lgI2cReadI2CBlockData(int handle, int i2cReg, char *rxBuf, int count)

    This reads count bytes from the specified register of the device. The count may be 1-32.
        handle: >= 0 (as returned by lgI2cOpen)
        i2cReg: 0-255, the register to read
         rxBuf: an array to receive the read data
         count: 1-32, the number of bytes to read
    If OK returns the count of bytes read (0-32) and updates rxBuf.
    On failure returns a negative error code.
        S Addr Wr [A] i2cReg [A]
           S Addr Rd [A] [rxBuf0] A [rxBuf1] A ... A [rxBufn] NA P

int lgI2cWriteI2CBlockData(int handle, int i2cReg, const char *txBuf, int count)

    This writes 1 to 32 bytes to the specified register of the device.
        handle: >= 0 (as returned by lgI2cOpen)
        i2cReg: 0-255, the register to write
         txBuf: 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] i2cReg [A] txBuf0 [A] txBuf1 [A] ... [A] txBufn [A] P

int lgI2cReadDevice(int handle, char *rxBuf, int count)

    This reads count bytes from the raw device into rxBuf.
        handle: >= 0 (as returned by lgI2cOpen)
         rxBuf: an array to receive the read data bytes
         count: >0, the number of bytes to read
    If OK returns count (>0) and updates rxBuf.
    On failure returns a negative error code.
        S Addr Rd [A] [rxBuf0] A [rxBuf1] A ... A [rxBufn] NA P

int lgI2cWriteDevice(int handle, const char *txBuf, int count)

    This writes count bytes from txBuf to the raw device.
        handle: >= 0 (as returned by lgI2cOpen)
         txBuf: 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] txBuf0 [A] txBuf1 [A] ... [A] txBufn [A] P

int lgI2cSegments(int handle, lgI2cMsg_t *segs, int count)

    This function executes multiple I2C segments in one transaction by calling the I2C_RDWR ioctl.
        handle: >= 0 (as returned by lgI2cOpen)
          segs: an array of I2C segments
         count: >0, the number of I2C segments
    If OK returns the number of segments executed.
    On failure returns a negative error code.

int lgI2cZip(int handle, const char *txBuf, int txCount, char *rxBuf, int rxCount)

    This function executes a sequence of I2C operations. The operations to be performed are specified by the contents of txBuf which contains the concatenated command codes and associated data.
          handle: >= 0 (as returned by lgI2cOpen)
           txBuf: pointer to the concatenated I2C commands, see below
         txCount: size of command buffer
           rxBuf: pointer to buffer to hold returned data
         rxCount: size of receive buffer
    If OK returns the count of bytes read (which may be 0) and updates rxBuf.
    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
    Address 2 P Set I2C address to P
    Flags 3 lsb msb Set I2C flags to lsb + (msb << 8)
    Read 4 P Read P bytes of data
    Write 5 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 rxBuf.
    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
        2 0x53  5 1 0x32  4 6
        2 0x1E  5 1 0x03  4 6
        2 0x68  5 1 0x1B  4 8
        0

int lgSerialOpen(const char *serDev, int serBaud, int serFlags)

    This function opens a serial device at a specified baud rate and with specified flags.
          serDev: the serial device to open
         serBaud: the baud rate in bits per second, see below
        serFlags: 0
    If OK returns a handle (>= 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 lgSerialClose(int handle)

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

int lgSerialWriteByte(int handle, int byteVal)

    This function writes the byte to the serial device.
         handle: >= 0 (as returned by lgSerialOpen)
        byteVal: the byte to write.
    If OK returns 0.
    On failure returns a negative error code.

int lgSerialReadByte(int handle)

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

int lgSerialWrite(int handle, const char *txBuf, int count)

    This function writes count bytes from txBuf to the the serial device.
        handle: >= 0 (as returned by lgSerialOpen)
         txBuf: 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 lgSerialRead(int handle, char *rxBuf, int count)

    This function reads up count bytes from the the serial device and writes them to rxBuf.
        handle: >= 0 (as returned by lgSerialOpen)
         rxBuf: an array to receive the read data
         count: the maximum number of bytes to read
    If OK returns the count of bytes read (>= 0) and updates rxBuf.
    On failure returns a negative error code.

int lgSerialDataAvailable(int handle)

    This function returns the count of bytes available to be read from the device.
        handle: >= 0 (as returned by lgSerialOpen)
    If OK returns the count of bytes available(>= 0).
    On failure returns a negative error code.

int lgSpiOpen(int spiDev, int spiChan, int spiBaud, int spiFlags)

    This function returns a handle for the SPI device on the channel.
          spiDev: >= 0
         spiChan: >= 0
         spiBaud: the SPI speed to set in bits per second
        spiFlags: see below
    If OK returns a handle (>= 0).
    On failure returns a negative error code.
    The flags may be used to modify the default behaviour.
    spiFlags 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 lgSpiClose(int handle)

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

int lgSpiRead(int handle, char *rxBuf, int count)

    This function reads count bytes of data from the SPI device.
        handle: >= 0 (as returned by lgSpiOpen)
         rxBuf: 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 rxBuf.
    On failure returns a negative error code.

int lgSpiWrite(int handle, const char *txBuf, int count)

    This function writes count bytes of data from txBuf to the SPI device.
        handle: >= 0 (as returned by lgSpiOpen)
         txBuf: 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 lgSpiXfer(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.
        handle: >= 0 (as returned by lgSpiOpen)
         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 *lgThreadStart(lgThreadFunc_t f, void *userdata)

    Starts a new thread of execution with f as the main routine.
               f: the main function for the new thread
        userdata: a pointer to arbitrary user data
    If OK returns a pointer to a pthread_t.
    On failure returns NULL.
    The function is passed the single argument arg.
    The thread can be cancelled by passing the pointer to pthread_t to lgThreadStop.
    Example
        #include <stdio.h>
        #include <unistd.h>
        #include <lgpio.h>
        void *myfunc(void *arg)
        {
           while (1)
           {
              printf("%s, (char *)arg);
              sleep(1);
           }
        }
        int main(int argc, char *argv[])
        {
           pthread_t *p1, *p2, *p3;
           p1 = lgThreadStart(myfunc, "thread 1"); sleep(3);
           p2 = lgThreadStart(myfunc, "thread 2"); sleep(3);
           p3 = lgThreadStart(myfunc, "thread 3"); sleep(3);
           lgThreadStop(p3); sleep(3);
           lgThreadStop(p2); sleep(3);
           lgThreadStop(p1); sleep(3);
        }

void lgThreadStop(pthread_t *pth)

    Cancels the thread pointed at by pth.
        pth: a thread pointer (as returned by lgThreadStart)
    No value is returned.
    The thread to be stopped should have been started with lgThreadStart.

uint64_t lguTimestamp(void)

    Returns the current timestamp.
    The timestamp is the number of nanoseconds since the epoch (start of 1970).

double lguTime(void)

    Returns the current time.
    The time is the number of seconds since the epoch (start of 1970).

void lguSleep(double sleepSecs)

    Sleeps for the specified number of seconds.
        sleepSecs: how long to sleep in seconds

int lguSbcName(char *rxBuf, int count)

    Copies the host name of the machine running the lgpio library to the supplied buffer. Up to count characters are copied.
        rxBuf: a buffer to receive the host name
        count: the size of the rxBuf
    If OK returns the count of bytes copied and updates rxBuf.
    On failure returns a negative error code.

int lguVersion(void)

    Returns the lgpiolibrary version number.

int lguGetInternal(int cfgId, uint64_t *cfgVal)

    Get an internal configuration value.
         cfgId: the item.
        cfgVal: a variable to receive the returned value
    If OK returns 0 and updates cfgVal.
    On failure returns a negative error code.

int lguSetInternal(int cfgId, uint64_t cfgVal)

    Set an internal configuration value.
         cfgId: the item
        cfgVal: the value to set
    If OK returns 0.
    On failure returns a negative error code.

const char *lguErrorText(int error)

    Returns the error text for an error code.
        error: the error code

void lguSetWorkDir(const char *dirPath)

    Sets the library working directory.
    This function has no affect if the working directory has already been set.
        dirPath: the directory to set as the working directory
    If dirPath does not start with a / the directory is relative to the library launch directory.

const char *lguGetWorkDir(void)

    Returns the library working directory.

PARAMETERS

bitVal
    A value of 0 or 1.

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

cbf An alerts callback function.

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

cfgVal
    The value of a configuration item.

*cfgVal
    The value of a configuration item.

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

chipInfo
    A pointer to a lgChipInfo_t object.

count
    The number of items.

debounce_us
    The debounce time in microseconds.

*dirPath
    A directory path which.

double
    A floating point number.

eFlags
    The type of GPIO edge to generate an alert. See lgGpioClaimAlert.
        LG_RISING_EDGE
        LG_FALLING_EDGE
        LG_BOTH_EDGES

error
    An error code. All error codes are negative.

f   A function.

float
    A floating point number

gpio
    A GPIO number, the offset of the GPIO from the base of the gpiochip. Offsets start at 0.

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

*gpios
    An array of GPIO numbers.

*gpiouser
    A string of up to 32 characters denoting the user of a GPIO.

groupBits
    A 64-bit value used to set the levels of a 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 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 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
    lgGpiochipOpen
    lgI2cOpen
    lgNotifyOpen
    lgSerialOpen
    lgSpiOpen

i2cAddr: 0-0x7F
    The address of a device on the I2C bus.

i2cDev: >= 0
    An I2C device number.

i2cFlags: 0
    Flags which modify an I2C open command. None are currently defined.

i2cReg: 0-255
    A register of an I2C device.

int A whole number, negative or positive.

*ioBuf
    A pointer to a buffer used to hold data to send and the data received.

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

level
    A GPIO level (0 or 1).

*levels
    An array of GPIO levels.

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;

lgGpioAlert_t
        typedef struct lgGpioAlert_s
        {
           lgGpioReport_t report;
           int nfyHandle;
        } lgGpioAlert_t, *lgGpioAlert_p;
    See lgGpioReport_t.

lgGpioAlertsFunc_t
        typedef void (*lgGpioAlertsFunc_t)
           (int num_alerts, lgGpioAlert_p alerts, void *userdata);
    See lgGpioAlert_t.

lgGpioReport_t
        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=watchdog
           uint8_t flags;      // none defined, ignore report if non-zero
        } lgGpioReport_t;

lgI2cMsg_t
        typedef struct
        {
           uint16_t addr;  // slave address
           uint16_t flags;
           uint16_t len;   // msg length
           uint8_t  *buf;  // pointer to msg data
        } lgI2cMsg_t;

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.

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

*pth
    A thread identifier, returned by lgGpioStartThread.

pthread_t
    A thread identifier.

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

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

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

pulseOn: >= 0
    The on period for a PWM 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 used to receive data.

rxCount
    The size of an input buffer.

*segs
    An array of segments which make up a combined I2C transaction.

serBaud
    The speed of serial communication in bits per second.

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

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

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.

sleepSecs: >= 0.0
    The number of seconds to sleep (may be fractional).

spiBaud
    The speed of serial communication in bits per second.

spiChan
    A SPI channel, >= 0.

spiDev
    A SPI device, >= 0.

spiFlags
    See lgSpiOpen.

*txBuf
    An pointer to a buffer of data to transmit.

txCount
    The size of an output buffer.

uint64_t
    A 64-bit unsigned value.

*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);

void
    Denoting no parameter is required.

watchdog_us
    The watchdog time in microseconds.

wordVal: 0-65535
    A 16-bit value.

Error Codes
    LG_OKAY                   0 // No error
    LG_INIT_FAILED           -1 // initialisation failed
    LG_BAD_MICROS            -2 // micros not 0-999999
    LG_BAD_PATHNAME          -3 // can not open pathname
    LG_NO_HANDLE             -4 // no handle available
    LG_BAD_HANDLE            -5 // unknown handle
    LG_BAD_SOCKET_PORT       -6 // socket port not 1024-32000
    LG_NOT_PERMITTED         -7 // GPIO operation not permitted
    LG_SOME_PERMITTED        -8 // one or more GPIO not permitted
    LG_BAD_SCRIPT            -9 // invalid script
    LG_BAD_TX_TYPE          -10 // bad tx type for GPIO and group
    LG_GPIO_IN_USE          -11 // GPIO already in use
    LG_BAD_PARAM_NUM        -12 // script parameter id not 0-9
    LG_DUP_TAG              -13 // script has duplicate tag
    LG_TOO_MANY_TAGS        -14 // script has too many tags
    LG_BAD_SCRIPT_CMD       -15 // illegal script command
    LG_BAD_VAR_NUM          -16 // script variable id not 0-149
    LG_NO_SCRIPT_ROOM       -17 // no more room for scripts
    LG_NO_MEMORY            -18 // can not allocate temporary memory
    LG_SOCK_READ_FAILED     -19 // socket read failed
    LG_SOCK_WRIT_FAILED     -20 // socket write failed
    LG_TOO_MANY_PARAM       -21 // too many script parameters (> 10)
    LG_SCRIPT_NOT_READY     -22 // script initialising
    LG_BAD_TAG              -23 // script has unresolved tag
    LG_BAD_MICS_DELAY       -24 // bad MICS delay (too large)
    LG_BAD_MILS_DELAY       -25 // bad MILS delay (too large)
    LG_I2C_OPEN_FAILED      -26 // can not open I2C device
    LG_SERIAL_OPEN_FAILED   -27 // can not open serial device
    LG_SPI_OPEN_FAILED      -28 // can not open SPI device
    LG_BAD_I2C_BUS          -29 // bad I2C bus
    LG_BAD_I2C_ADDR         -30 // bad I2C address
    LG_BAD_SPI_CHANNEL      -31 // bad SPI channel
    LG_BAD_I2C_FLAGS        -32 // bad I2C open flags
    LG_BAD_SPI_FLAGS        -33 // bad SPI open flags
    LG_BAD_SERIAL_FLAGS     -34 // bad serial open flags
    LG_BAD_SPI_SPEED        -35 // bad SPI speed
    LG_BAD_SERIAL_DEVICE    -36 // bad serial device name
    LG_BAD_SERIAL_SPEED     -37 // bad serial baud rate
    LG_BAD_FILE_PARAM       -38 // bad file parameter
    LG_BAD_I2C_PARAM        -39 // bad I2C parameter
    LG_BAD_SERIAL_PARAM     -40 // bad serial parameter
    LG_I2C_WRITE_FAILED     -41 // i2c write failed
    LG_I2C_READ_FAILED      -42 // i2c read failed
    LG_BAD_SPI_COUNT        -43 // bad SPI count
    LG_SERIAL_WRITE_FAILED  -44 // ser write failed
    LG_SERIAL_READ_FAILED   -45 // ser read failed
    LG_SERIAL_READ_NO_DATA  -46 // ser read no data available
    LG_UNKNOWN_COMMAND      -47 // unknown command
    LG_SPI_XFER_FAILED      -48 // spi xfer/read/write failed
    LG_BAD_POINTER          -49 // bad (NULL) pointer
    LG_MSG_TOOBIG           -50 // socket/pipe message too big
    LG_BAD_MALLOC_MODE      -51 // bad memory allocation mode
    LG_TOO_MANY_SEGS        -52 // too many I2C transaction segments
    LG_BAD_I2C_SEG          -53 // an I2C transaction segment failed
    LG_BAD_SMBUS_CMD        -54 // SMBus command not supported by driver
    LG_BAD_I2C_WLEN         -55 // bad I2C write length
    LG_BAD_I2C_RLEN         -56 // bad I2C read length
    LG_BAD_I2C_CMD          -57 // bad I2C command
    LG_FILE_OPEN_FAILED     -58 // file open failed
    LG_BAD_FILE_MODE        -59 // bad file mode
    LG_BAD_FILE_FLAG        -60 // bad file flag
    LG_BAD_FILE_READ        -61 // bad file read
    LG_BAD_FILE_WRITE       -62 // bad file write
    LG_FILE_NOT_ROPEN       -63 // file not open for read
    LG_FILE_NOT_WOPEN       -64 // file not open for write
    LG_BAD_FILE_SEEK        -65 // bad file seek
    LG_NO_FILE_MATCH        -66 // no files match pattern
    LG_NO_FILE_ACCESS       -67 // no permission to access file
    LG_FILE_IS_A_DIR        -68 // file is a directory
    LG_BAD_SHELL_STATUS     -69 // bad shell return status
    LG_BAD_SCRIPT_NAME      -70 // bad script name
    LG_CMD_INTERRUPTED      -71 // Python socket command interrupted
    LG_BAD_EVENT_REQUEST    -72 // bad event request
    LG_BAD_GPIO_NUMBER      -73 // bad GPIO number
    LG_BAD_GROUP_SIZE       -74 // bad group size
    LG_BAD_LINEINFO_IOCTL   -75 // bad lineinfo IOCTL
    LG_BAD_READ             -76 // bad GPIO read
    LG_BAD_WRITE            -77 // bad GPIO write
    LG_CANNOT_OPEN_CHIP     -78 // can not open gpiochip
    LG_GPIO_BUSY            -79 // GPIO busy
    LG_GPIO_NOT_ALLOCATED   -80 // GPIO not allocated
    LG_NOT_A_GPIOCHIP       -81 // not a gpiochip
    LG_NOT_ENOUGH_MEMORY    -82 // not enough memory
    LG_POLL_FAILED          -83 // GPIO poll failed
    LG_TOO_MANY_GPIOS       -84 // too many GPIO
    LG_UNEGPECTED_ERROR     -85 // unexpected error
    LG_BAD_PWM_MICROS       -86 // bad PWM micros
    LG_NOT_GROUP_LEADER     -87 // GPIO not the group leader
    LG_SPI_IOCTL_FAILED     -88 // SPI iOCTL failed
    LG_BAD_GPIOCHIP         -89 // bad gpiochip
    LG_BAD_CHIPINFO_IOCTL   -90 // bad chipinfo IOCTL
    LG_BAD_CONFIG_FILE      -91 // bad configuration file
    LG_BAD_CONFIG_VALUE     -92 // bad configuration value
    LG_NO_PERMISSIONS       -93 // no permission to perform action
    LG_BAD_USERNAME         -94 // bad user name
    LG_BAD_SECRET           -95 // bad secret for user
    LG_TX_QUEUE_FULL        -96 // TX queue full
    LG_BAD_CONFIG_ID        -97 // bad configuration id
    LG_BAD_DEBOUNCE_MICS    -98 // bad debounce microseconds
    LG_BAD_WATCHDOG_MICS    -99 // bad watchdog microseconds
    LG_BAD_SERVO_FREQ      -100 // bad servo frequency
    LG_BAD_SERVO_WIDTH     -101 // bad servo pulsewidth
    LG_BAD_PWM_FREQ        -102 // bad PWM frequency
    LG_BAD_PWM_DUTY        -103 // bad PWM dutycycle
    LG_GPIO_NOT_AN_OUTPUT  -104 // GPIO not set as an output
    LG_INVALID_GROUP_ALERT -105 // can not set a group to alert

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