.\" man page for Munts Technologies Linux Simple I/O Library
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.\" Copyright (C)2016-2023, Philip Munts dba Munts Technologies.
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.TH libpwm 2 "21 December 2018" "version 1" "Linux Simple I/O Library"
.SH NAME
.B libpwm
\-\- Linux Simple I/O Library: PWM Output Module
.SH SYNOPSIS
.nf
.B #include <libsimpleio/libpwm.h>

.B typedef enum
.B {
.B "  PWM_POLARITY_ACTIVELOW,"
.B "  PWM_POLARITY_ACTIVEHIGH,"
.B } PWM_POLARITY_t;

.BI "void PWM_configure(int32_t " chip ", int32_t " channel ", int32_t " period ",
.BI "  int32_t " ontime ", int32_t " polarity ", int32_t *" error ");"

.BI "void PWM_open(int32_t " chip ", int32_t " channel ", int32_t *" fd ",
.BI "  int32_t *" error ");"

.BI "void PWM_close(int32_t " fd ", int32_t *" error ");"

.BI "void PWM_write(int32_t " fd ", int32_t " ontime ", int32_t *" error ");"

.fi
Link with
.BR -lsimpleio .
.SH DESCRIPTION
.nh
All functions return either
.B 0
(upon success) or an
.B errno
value (upon failure) in
.IR *error .
.PP
.B PWM_configure()
configures a single PWM output.  The
.I chip
parameter selects the PWM controller chip (as numbered by the Linux kernel) and the
.I channel
parameter selects the PWM output (also as numbered by the Linux kernel) to be configured.
The
.I period
parameter sets the PWM output pulse period in nanoseconds.  Note that many PWM controllers
require the same PWM pulse frequency for all channels.  Therefore, configuring different
pulse period values for different channels within the same PWM controller may result
in incorrect operation.
The
.I ontime
parameter sets the initial PWM output pulse width in nanoseconds.
The
.I polarity
parameter sets the PWM output polarity and may be
.B PWM_POLARITY_ACTIVELOW
or
.BR PWM_POLARITY_ACTIVEHIGH .
Note that some PWM controllers will not allow the
.B PWM_POLARITY_ACTIVELOW
setting.
.PP
.B PWM_open()
opens a (previously) configured PWM output device. The PWM controller chip number must be passed in the
.I chip
parameter and the PWM output number must be passed in the
.I channel
parameter.  Upon success, a file descriptor for the PWM output device is returned in
.IR *fd .
.PP
.B PWM_close()
closes a previously opened PWM output device.
.PP
.B PWM_write()
changes the PWM output pulse width.  The file descriptor for an open PWM output device
must be passed in the
.I fd
parameter.  The new PWM output pulse width in nanoseconds must be passed in the
.I ontime
parameter.
.SH SEE ALSO
.BR libsimpleio "(2), " libadc "(2), " libdac "(2), " libevent "(2), " libgpio "(2),"
.br
.BR libhidraw "(2), " libi2c "(2), " libipv4 "(2), " liblinux "(2), " liblinx "(2),"
.br
.BR libserial "(2), " libspi "(2), " libstream "(2), " libwatchdog "(2)"
.SH AUTHOR
Philip Munts dba Munts Technologies.