GPIO to start script?

[gmc]

I've managed to setup a headless Pi with mpc which streams internet radio and plays via my bluetooth speakers. Since this is headless I want to setup a on/off switch where when when the button is off it will run this once:

Code: Select all

mpc stop

And when the button is in the on position it will run this once:

Code: Select all

mpc play 1

I thought I could have a script running which monitors one of the GPIO pins and when it changes state then run a script to start/stop the radio. The problem is it only needs to run this once.

Any ideas on how I go about doing this?

[rpdom]

If I understand correctly, you want something to run a command every time the switch changes, yes?

So perhaps if you set a script running that does something like this

Code: Select all

Set_up_gpio
oldstate = read_gpio
while True
    state = read_gpio
    if state != oldstate
        if state == 1
            run "on" command
        else
            run "off" command
        endif
        oldstate = state
    endif
    sleep a bit
endwhile

That's not real code, just the flow of the program. I'll let you write the code in your preferred language

[gmc]

Thanks - just what I was looking for. I couldn't get my head around the logic but it seems pretty simple with your script.

[Massi]

use interrupts instead of wasting cpu

[gmc]

Good idea - will use interrupts.

[rpdom]

It won't waste much cpu with a short sleep in there, even 0.1 second would do it.