dotfiles/pi/boot.go

// =============================================================================
// Auth: alex
// File: boot.go
// Revn: 06-16-2026  2.0
// Func: Blink a light when the pi boots (or on login, but who cares)
//
// TODO: create
// =============================================================================
// CHANGE LOG
// -----------------------------------------------------------------------------
// 06-23-2022: init
//*10-10-2023: imported flag
//             added flag to define gpio pin at runtime
//*06-16-2026: added flag to control flash duration
//             added flag to control amount of flashes
//             added flag to decide between flash mode and toggle mode
//
// =============================================================================

package main


import (
    "flag"      // IntVar, BoolVar, Float64Var, Parse
    "fmt"       // Println
    // rpio.Pin, Pin, Open, Close, Output, Toggle
    "github.com/stianeikeland/go-rpio"
    "os"        // Exit
    "time"      // Sleep, time.Second
)


/*
Toggles a LED on physical pin 19 (mcu pin 10)
Connect a LED with resistor from pin 19 to ground.
*/


var pin rpio.Pin    // global pin object
var num int         // flag variable, holds pin number
var dur float64     // flag variable, holds duration
var amt int         // flag variable, holds times to flash
var tog bool        // flag variable, hold toggle mode switch

func main() {

    // map input flag to variable
    flag.IntVar( &num, "p", 10, "pin number" )
    flag.Float64Var( &dur, "d", 100, "duration of flash (ms)" )
    flag.IntVar( &amt, "n", 2, "amount of times to flash" )
    flag.BoolVar( &tog, "t", false, "toggle mode" )
    flag.Parse()

    // create pin object at given pin number
    pin = rpio.Pin( num )
    // Open and map memory to access gpio, check for errors
    if err := rpio.Open(); err != nil {
        fmt.Println( "Fatal: pin open failed" )
        fmt.Println( "Error: ", err.Error() )
        os.Exit(1)
    }

    // Unmap gpio memory when done
    defer rpio.Close()

    // Set pin to output mode
    pin.Output()

    if tog {            // if user specifies toggle mode
        pin.Toggle()    // toggle
        return          // and leave
    }

    // Toggle pin 2*amt times
    for i := 0; i < 2 * amt; i++ {
        pin.Toggle()
        time.Sleep( time.Millisecond * time.Duration( dur ) )
    }
}