PWM Tool

This is a simple Linux command line tool designed to control the available PWM channels via the sysfs interface. The main purpose of this utility is to control a buzzer device connected to the corresponding PWM channel.

Build and Install

Clone tool sources (for example, to ~/pwm-tool directory):

$ git clone https://github.com/tano-systems/pwm-tool.git ~/pwm-tool

Jump to the directory with sources:

$ cd ~/pwm-tool

Create a build subdirectory and jump to it:

$ mkdir build
$ cd build

Run CMake:

$ cmake ../

Run Make:

$ make

This will produce binary pwm in the build directory. To install this binary to /usr/bin run command as root user:

# make install

Tests

To run unit tests use following command:

$ make build_and_test

Usage

Usage syntax:

pwm [options]

• [options] is a one or more additional optional options that are described in the "Options" section.

Options

Short Form	Long Form	Default Value	Description
-h	--help	-	Display help and usage text.
-p <chip>	--chip=<chip>	0	Set PWM chip number to <chip>
-c <channel>	--channel=<channel>	0	Set PWM channel number to <channel>
-f <freq_hz>	--frequency=<freq_hz>	1000	Set PWM frequency in Hz. If the specified frequency is 0, the PWM will not be enabled.
-d <duration_ms>	--duration=<duration_ms>	250	Set PWM enabled state duration in milliseconds.
-k	--keep-enabled	-	If specified, PWM will remain enabled on exit.
-s <script>	--script=<script>	-	Run PWM commands script. See details in "Scripts Syntax" section.
-	--version	-	Display PWM tool version.

Scripts Syntax

The script consists of commands separated by one or more spaces:

<command1> <command2> ... <commandN>

Each command consists of one or more operations, which are stored one after the other without spaces:

<op1><op2>...<opN>

The operation is represented by a single character of the alphabet. Operation can have only one optional numeric argument, which must be written immediately after the operation character:

O[argument]

For example, the operation F with the argument 1250 should be written as follows:

F1250

And a command consisting of two operations, F with argument 1250 and d with argument 50, as follows:

F1250d50

Examples of how to write multiple commands can be seen in the "Examples" section.

Available PWM command operations:

Operation	Description
f[hz]	Set frequency from optional argument. If no argument is specified, the current default frequency will be used.
F[hz]	Same as f[hz], but if an argument is specified, the value will then be used as the default frequency for subsequent commands.
d[ms]	Set duration from optional argument. If no argument is specified, the current default duration will be used.
D[ms]	Same as d[ms], but if an argument is specified, the value will then be used as the default duration for subsequent commands.
k	Keep the PWM enabled when the command is completed.

If no f or F operation is specified in a command, then a frequency of 0 will be used for that command, i.e. such commands can be used to delay script execution.

If no d or D operation is specified in a command, the current default duration will be used for that command. Changing the default duration can either be done through the configuration structure or directly at runtime with the D[ms] operation.

Examples

Three short beeps with a frequency of 1000 Hz (duration 100 ms with 50 ms delay between):

$ pwm -f 1000 -d 100
$ pwm -f 0 -d 50
$ pwm -f 1000 -d 100
$ pwm -f 0 -d 50
$ pwm -f 1000 -d 100

Same for PWM commands script mode:

$ pwm -s "F1000D100 d50 f d50 f"

Changelog

See CHANGELOG.md.

License

This work is free. You can redistribute it and/or modify it under the terms of the Do What The Fuck You Want To Public License, Version 2, as published by Sam Hocevar. See http://www.wtfpl.net/ for more details.

Maintainers

• Anton Kikin mailto:[email protected]