Quick and Dirty Pi PWM Generator

pwm.go

// Quick and Dirty PWM tool in Golang to pulse Pin 18 (PWM) on Raspberry PI at a set frequency, and duty cycle
// Usage: ./pwm <frequency> <duty> <period>
// e.g. For 32kHz with a duty cycle of 1/4:
// sudo ./pwm 32000 1 4
// Must run as root for now, I haven't had time to write a udev rule for /dev/mem
package main

import (
	"fmt"
	"log"
	"os"
	"strconv"
	"time"

	"github.com/stianeikeland/go-rpio/v4"
)

func main() {

	fmt.Println("parse args")
	args := os.Args

	if len(args) < 4 {
		fmt.Printf("usage: %s <freq> <duty> <period>\n", args[0])
		os.Exit(1)
	}

	fmt.Println("open memory")
	err := rpio.Open()
	if err != nil {
		log.Fatal(err)
	}

	defer rpio.Close()

	fmt.Println("select pin 18")
	pin := rpio.Pin(18)

	fmt.Println("set pin mode to pwm")
	pin.Mode(rpio.Pwm)

	frq, err := strconv.ParseInt(args[1], 10, 64)
	if err != nil {
		fmt.Printf("failed to parse frequency value: %q\n", args[0])
	}

	duty, err := strconv.ParseUint(args[2], 10, 32)
	if err != nil {
		fmt.Printf("failed to parse duty length value: %q\n", args[0])
	}

	period, err := strconv.ParseUint(args[3], 10, 32)
	if err != nil {
		fmt.Printf("failed to parse period value: %q\n", args[0])
	}

	fmt.Printf("set frequency to %d\n", int(frq))
	pin.Freq(int(frq))
	fmt.Printf("set duty cycle to %d/%d\n", uint32(duty), uint32(period))
	pin.DutyCycle(uint32(duty), uint32(period))

	for {
		time.Sleep(time.Second)
		fmt.Print(".")
	}

}

Output is pretty accurate ~32kHz and ~3.3V