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lgpio.3
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.\" Process this file with
.\" groff -man -Tascii lg.3
.\"
.TH lgpio 3 2020-2023 Linux "lg archive"
.SH NAME
lgpio - A C library to manipulate a local SBC's GPIO.
.SH SYNOPSIS
#include <lgpio.h>
gcc -Wall -o prog prog.c -llgpio
\&./prog
.SH DESCRIPTION
.ad l
.nh
.br
.br
lgpio is a C library for Linux Single Board Computers which
allows control of the General Purpose Input Output pins.
.br
.br
.SS Features
.br
.br
.br
o reading and writing GPIO singly and in groups
.br
o software timed PWM and waves
.br
o GPIO callbacks
.br
o pipe notification of GPIO alerts
.br
o I2C wrapper
.br
o SPI wrapper
.br
o serial link wrapper
.br
o a simple interface to start and stop new threads
.br
.br
.SS Usage
.br
.br
Include <lgpio.h> in your source files.
.br
.br
Assuming your source is in a single file called prog.c use the following
command to build and run the executable.
.br
.br
.EX
gcc -Wall -o prog prog.c -llgpio
.br
./prog
.br
.EE
.br
.br
For examples of usage see the C programs within the lg archive file.
.br
.br
.SS Notes
.br
.br
All the functions which return an int return < 0 on error.
.br
.br
.SH OVERVIEW
.br
.SS GPIO
.br
.br
lgGpiochipOpen Opens a gpiochip device
.br
lgGpiochipClose Closes a gpiochip device
.br
.br
lgGpioGetChipInfo Gets gpiochip information
.br
lgGpioGetLineInfo Gets gpiochip line information
.br
lgGpioGetMode Gets the mode of a GPIO
.br
.br
lgGpioSetUser Notifies Linux of the GPIO user
.br
.br
lgGpioClaimInput Claims a GPIO for input
.br
lgGpioClaimOutput Claims a GPIO for output
.br
lgGpioClaimAlert Claims a GPIO for alerts
.br
lgGpioFree Frees a GPIO
.br
.br
lgGroupClaimInput Claims a group of GPIO for inputs
.br
lgGroupClaimOutput Claims a group of GPIO for outputs
.br
lgGroupFree Frees a group of GPIO
.br
.br
lgGpioRead Reads a GPIO
.br
lgGpioWrite Writes a GPIO
.br
.br
lgGroupRead Reads a group of GPIO
.br
lgGroupWrite Writes a group of GPIO
.br
.br
lgTxPulse Starts pulses on a GPIO
.br
lgTxPwm Starts PWM pulses on a GPIO
.br
lgTxServo Starts Servo pulses on a GPIO
.br
lgTxWave Starts a wave on a group of GPIO
.br
lgTxBusy See if tx is active on a GPIO or group
.br
lgTxRoom See if more room for tx on a GPIO or group
.br
.br
lgGpioSetDebounce Sets the debounce time for a GPIO
.br
lgGpioSetWatchdog Sets the watchdog time for a GPIO
.br
.br
lgGpioSetAlertsFunc Starts a GPIO callback
.br
lgGpioSetSamplesFunc Starts a GPIO callback for all GPIO
.br
.SS I2C
.br
.br
lgI2cOpen Opens an I2C device
.br
lgI2cClose Closes an I2C device
.br
.br
lgI2cWriteQuick SMBus write quick
.br
.br
lgI2cReadByte SMBus read byte
.br
lgI2cWriteByte SMBus write byte
.br
.br
lgI2cReadByteData SMBus read byte data
.br
lgI2cWriteByteData SMBus write byte data
.br
.br
lgI2cReadWordData SMBus read word data
.br
lgI2cWriteWordData SMBus write word data
.br
.br
lgI2cReadBlockData SMBus read block data
.br
lgI2cWriteBlockData SMBus write block data
.br
.br
lgI2cReadI2CBlockData SMBus read I2C block data
.br
lgI2cWriteI2CBlockData SMBus write I2C block data
.br
.br
lgI2cReadDevice Reads the raw I2C device
.br
lgI2cWriteDevice Writes the raw I2C device
.br
.br
lgI2cProcessCall SMBus process call
.br
lgI2cBlockProcessCall SMBus block process call
.br
.br
lgI2cSegments Performs multiple I2C transactions
.br
lgI2cZip Performs multiple I2C transactions
.br
.SS NOTIFICATIONS
.br
.br
lgNotifyOpen Request a notification
.br
lgNotifyClose Close a notification
.br
lgNotifyPause Pause notifications
.br
lgNotifyResume Start notifications
.br
.SS SERIAL
.br
.br
lgSerialOpen Opens a serial device
.br
lgSerialClose Closes a serial device
.br
.br
lgSerialReadByte Reads a byte from a serial device
.br
lgSerialWriteByte Writes a byte to a serial device
.br
.br
lgSerialRead Reads bytes from a serial device
.br
lgSerialWrite Writes bytes to a serial device
.br
.br
lgSerialDataAvailable Returns number of bytes ready to be read
.br
.SS SPI
.br
.br
lgSpiOpen Opens a SPI device
.br
lgSpiClose Closes a SPI device
.br
.br
lgSpiRead Reads bytes from a SPI device
.br
lgSpiWrite Writes bytes to a SPI device
.br
.br
lgSpiXfer Transfers bytes with a SPI device
.br
.SS THREADS
.br
.br
lgThreadStart Start a new thread
.br
lgThreadStop Stop a previously started thread
.br
.SS UTILITIES
.br
.br
lguVersion Gets the library version
.br
lguSbcName Gets the host name of the SBC
.br
.br
lguGetInternal Get an internal configuration value
.br
lguSetInternal Set an internal configuration value
.br
.br
lguSleep Sleeps for a given time
.br
.br
lguTimestamp Gets the current timestamp
.br
lguTime Gets the current time
.br
.br
lguErrorText Gets a text description of an error code
.br
.br
lguSetWorkDir Set the working directory
.br
lguGetWorkDir Get the working directory
.br
.SH FUNCTIONS
.IP "\fBint lgGpiochipOpen(int gpioDev)\fP"
.IP "" 4
This returns a handle to a gpiochip device.
.br
.br
.EX
gpioDev: >= 0
.br
.EE
.br
.br
If OK returns a handle (>= 0).
.br
.br
On failure returns a negative error code.
.br
.br
\fBExample\fP
.br
.EX
h = lgGpiochipOpen(0); // open /dev/gpiochip0
.br
.br
if (h >= 0)
.br
{
.br
// open ok
.br
}
.br
else
.br
{
.br
// open error
.br
}
.br
.EE
.IP "\fBint lgGpiochipClose(int handle)\fP"
.IP "" 4
This closes an opened gpiochip device.
.br
.br
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
.EE
.br
.br
If OK returns 0.
.br
.br
On failure returns a negative error code.
.br
.br
\fBExample\fP
.br
.EX
status = lgGpiochipClose(h); // close gpiochip
.br
.br
if (status < 0)
.br
{
.br
// close failed
.br
}
.br
.EE
.IP "\fBint lgGpioGetChipInfo(int handle, lgChipInfo_p chipInfo)\fP"
.IP "" 4
This returns information about a gpiochip.
.br
.br
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
chipInfo: A pointer to space for a lgChipInfo_t object
.br
.EE
.br
.br
If OK returns 0 and updates chipInfo.
.br
.br
On failure returns a negative error code.
.br
.br
This command gets the number of GPIO on the gpiochip,
its name, and its usage.
.br
.br
\fBExample\fP
.br
.EX
lgChipInfo_t cInfo;
.br
.br
status = lgGpioGetChipInfo(h, &cInfo);
.br
.br
if (status == LG_OKAY)
.br
{
.br
printf("lines=%d name=%s label=%s\n",
.br
cInfo.lines, cInfo.name, cInfo.label))
.br
}
.br
.EE
.IP "\fBint lgGpioGetLineInfo(int handle, int gpio, lgLineInfo_p lineInfo)\fP"
.IP "" 4
Returns information about a GPIO.
.br
.br
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
gpio: >= 0, as legal for the gpiochip
.br
lineInfo: A pointer to space for a lgLineInfo_t object
.br
.EE
.br
.br
If OK returns 0 and updates lineInfo.
.br
.br
On failure returns a negative error code.
.br
.br
This command gets information for a GPIO of a gpiochip. In particular
it gets the GPIO number, flags, its user, and its purpose.
.br
.br
The meaning of the flags bits are as given for the mode by \fBlgGpioGetMode\fP.
.br
.br
The user and purpose fields are filled in by the software which has
claimed the GPIO and may be blank.
.br
.br
\fBExample\fP
.br
.EX
lgLineInfo_t lInfo;
.br
.br
status = lgGpioGetLineInfo(h, gpio, &lInfo);
.br
.br
if (status == LG_OKAY)
.br
{
.br
printf("lFlags=%d name=%s user=%s\n",
.br
lInfo.lFlags, lInfo.name, lInfo.user))
.br
}
.br
.EE
.IP "\fBint lgGpioGetMode(int handle, int gpio)\fP"
.IP "" 4
Returns the GPIO mode.
.br
.br
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
gpio: >= 0, as legal for the gpiochip
.br
.EE
.br
.br
If OK returns the GPIO mode.
.br
.br
On failure returns a negative error code.
.br
.br
Bit Value Meaning
.br
0 1 Kernel: In use by the kernel
.br
1 2 Kernel: Output
.br
2 4 Kernel: Active low
.br
3 8 Kernel: Open drain
.br
4 16 Kernel: Open source
.br
5 32 Kernel: Pull up set
.br
6 64 Kernel: Pull down set
.br
7 128 Kernel: Pulls off set
.br
8 256 LG: Input
.br
9 512 LG: Output
.br
10 1024 LG: Alert
.br
11 2048 LG: Group
.br
12 4096 LG: ---
.br
13 8192 LG: ---
.br
14 16384 LG: ---
.br
15 32768 LG: ---
.br
16 65536 Kernel: Input
.br
17 1<<17 Kernel: Rising edge alert
.br
18 1<<18 Kernel: Falling edge alert
.br
19 1<<19 Kernel: Realtime clock alert
.br
.br
.br
The LG bits are only set if the query was made by the process that
owns the GPIO.
.IP "\fBint lgGpioSetUser(int handle, const char *gpiouser)\fP"
.IP "" 4
This sets the user string to be associated with each claimed GPIO.
.br
.br
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
gpiouser: a string up to 32 characters long
.br
.EE
.br
.br
If OK returns 0.
.br
.br
On failure returns a negative error code.
.br
.br
\fBExample\fP
.br
.EX
status = lgGpioSetUser(h, "my_title");
.br
.EE
.IP "\fBint lgGpioClaimInput(int handle, int lFlags, int gpio)\fP"
.IP "" 4
This claims a GPIO for input.
.br
.br
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
lFlags: line flags for the GPIO
.br
gpio: the GPIO to be claimed
.br
.EE
.br
.br
If OK returns 0.
.br
.br
On failure returns a negative error code.
.br
.br
The line flags may be used to set the GPIO
as active low, open drain, or open source.
.br
.br
\fBExample\fP
.br
.EX
// open GPIO 23 for input
.br
status = lgGpioClaimInput(h, 0, 23);
.br
.EE
.IP "\fBint lgGpioClaimOutput(int handle, int lFlags, int gpio, int level)\fP"
.IP "" 4
This claims a GPIO for output.
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
lFlags: line flags for the GPIO
.br
gpio: the GPIO to be claimed
.br
level: the initial level to set for the GPIO
.br
.EE
.br
.br
If OK returns 0.
.br
.br
On failure returns a negative error code.
.br
.br
The line flags may be used to set the GPIO
as active low, open drain, or open source.
.br
.br
If level is zero the GPIO will be initialised low. If any other
value is used the GPIO will be initialised high.
.br
.br
\fBExample\fP
.br
.EX
// open GPIO 31 for high output
.br
status = lgGpioClaimOutput(h, 0, 31, 1);
.br
.EE
.IP "\fBint lgGpioClaimAlert(int handle, int lFlags, int eFlags, int gpio, int nfyHandle)\fP"
.IP "" 4
This claims a GPIO for alerts on level changes.
.br
.br
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
lFlags: line flags for the GPIO
.br
eFlags: event flags for the GPIO
.br
gpio: >= 0, as legal for the gpiochip
.br
nfyHandle: >= 0 (as returned by \fBlgNotifyOpen\fP)
.br
.EE
.br
.br
If OK returns 0.
.br
.br
On failure returns a negative error code.
.br
.br
The line flags may be used to set the GPIO
as active low, open drain, or open source.
.br
.br
The event flags are used to specify alerts for a rising edge,
falling edge, or both edges.
.br
.br
The alerts will be sent to a previously opened notification. If
you don't want them sent to a notification set nfyHandle to -1.
.br
.br
The alerts will also be sent to any callback registered for the
GPIO by \fBlgGpioSetAlertsFunc\fP.
.br
.br
All GPIO alerts are also sent to a callback registered by
\fBlgGpioSetSamplesFunc\fP.
.br
.br
\fBExample\fP
.br
.EX
status = lgGpioClaimAlert(h, 0, LG_BOTH_EDGES, 16, -1);
.br
.EE
.IP "\fBint lgGpioFree(int handle, int gpio)\fP"
.IP "" 4
This frees a GPIO.
.br
.br
.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
.br
gpio: the GPIO to be freed
.br
.EE
.br
.br
If OK returns 0.
.br
.br
On failure returns a negative error code.
.br
.br
The GPIO may now be claimed by another user or for a different purpose.
.br
.br
\fBExample\fP
.br
.EX
status = lgGpioFree(h, 16);
.br
.EE
.IP "\fBint lgGroupClaimInput(int handle, int lFlags, int count, const int *gpios)\fP"
.IP "" 4
This claims a group of GPIO for inputs.
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.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
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lFlags: line flags for the GPIO group
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count: the number of GPIO to claim
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gpios: the group GPIO
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.EE
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If OK returns 0.
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On failure returns a negative error code.
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The line flags may be used to set the group
as active low, open drain, or open source.
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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.
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\fBExample\fP
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.EX
int buttons[4] = {9, 7, 2, 6};
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status = lgGroupClaimInput(h, 0, 4, buttons);
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if (status == LG_OKAY)
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{
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// OK
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}
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else
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{
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// Error
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}
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.EE
.IP "\fBint lgGroupClaimOutput(int handle, int lFlags, int count, const int *gpios, const int *levels)\fP"
.IP "" 4
This claims a group of GPIO for outputs.
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.EX
handle: >= 0 (as returned by \fBlgGpiochipOpen\fP)
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lFlags: line flags for the GPIO group
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count: the number of GPIO to claim
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