A PID controller for PWM devices

pwmpid is a PID controller written in POSIX shell for PWM hardware exposed by the Linux PWM API.

Features:

• POSIX shell script with effectively no dependencies.
• Anything that's a file containing a numerical value can be an input.
• Adjustable moving average of input values.
• Clamps on the integral error.
• Minimum duty cycle for starting mechanical consumers of the PWM output.
• No config verification or safety checks whats-o-ever.

Installation

Executing make install as root will install pwmpid and its service file into the default locations, make uninstall will remove them again.

Configuration

Configuration files are located under /etc/pwmpid and follow the naming scheme *chip*-*channel*.conf. For example a configuration file used for controlling /sys/class/pwm/pwmchip0/pwm0 would be /etc/pwmpid/pwmchip0-pwm0.conf.

The file pwmpid.conf.default is an example configuration file reflecting all the default values for pwmpid. All settings are optional; only values that need adjusting have to be specified in the actual configuration file -- which is probably most of them.

Usage

Running pwmpid manually

Running pwmpid manually can be especially useful for parameter tuning. Debug output for internal variables of the controller can be enabled by setting DEBUG=1 in the configuration file.

pwmpid pwchip0-pwm0

Running pwmpid as a systemd service

The service template in this repository allows systemd to control multiple instances with the chip/channel path as systemd-escaped instances name.

systemctl enable --now pwmpid@pwchip0-pwm0.service