Example golang application that makes use of the hardware PWM channels.

Written as an example for the Onion Omega2 but this would serve as a good example for a number of compute modules that have PWM hardware exposed to Linux.

gobot.io's sysfs module is used to provide access to the pwm hardware

The project has been updated to take advantage of go's new module support. This makes it easy to build.

<go to where you'd like to place the 'go-pwm-example' directory>
git clone https://github.com/chmorgan/go-pwm-example.git
cd go-pwm-example
go build

golang has support for a number of architectures built in, this makes it well suited for cross platform development.

The Omega2 uses a MediaTek MT7688 SoC. This processor is a mips architecture and little endian is being used. Therefore the architecture is 'mips' + 'le', or 'mipsle'.

GOOS=linux GOARCH=mipsle go build

You should now have a 'go-pwm-example' application in the current directory.

Replace 'xxxx' with the address of your Omega.

scp go-pwm-example [email protected]:/root/

Note: Pin muxing must be set appropriately for the pwm channel being used.

For example:

# omega2-ctrl gpiomux get
Group i2c - [i2c] gpio
Group uart0 - [uart] gpio
Group uart1 - [uart] gpio pwm01
Group uart2 - [uart] gpio pwm23
Group pwm0 - pwm [gpio]
Group pwm1 - pwm [gpio]
Group refclk - refclk [gpio]
Group spi_s - spi_s [gpio] pwm01_uart2
Group spi_cs1 - [spi_cs1] gpio refclk
Group i2s - i2s [gpio] pcm
Group ephy - [ephy] gpio
Group wled - wled [gpio]

Assuming we are using pwm channel 0 (GPIO18) you'll reconfigure this pin for pwm mode via:

# omega2-ctrl gpiomux set pwm0 pwm
set gpiomux pwm0 -> pwm

./go-pwm-example

And to get command line help you can pass the '-help' option:

# ./go-pwm-example -help
Usage of ./go-pwm-example:
  -channel int
    	PWM channel (0, 1, 2, or 3)
  -frequency float
    	Frequency in Hz (default 100)