raspi gpio fun

Last update: Thu Jun 5 22:25:41 2025

The idea is to add a few inputs/outputs on a Raspberry Pi puppy.

Presentation

Idea

I want a proper shutdown button for my webserver (Raspi 2) => I made a RaspiPower board for that.

I want to add some bling bling like blinking a led at each file served

Pilot so display to show message on a led board?

Points of interrest

Any pin is capable of GPIO. Not maybe 100% pure hardware (in terms of timing) but just any pin will be ok

RPi.GPIO lib can't do hardware PWM, all the PWM are software but at least you can have it on any pin

You can make the calls asynchronous by using the futures python package to run it on a threadpool

Implementation

Bill of materials

Schematics

OS Settings

Thanks to this person for sharing:

Need to run a Jessie raspbian so go for a sudo rpi-update and the usual sudo apt-get update ; sudo apt-get upgrade

If you do not run as root so the application user must be in the gpio group sudo adduser my-app-user gpio

And in case you still get a no access to /dev/mem, check the permissions and do sudo chown root.gpio /dev/gpiomem ; sudo chmod g+rw /dev/gpiomem

The above gpiomem change might be lost at reboot, so add it to your /etc/rc.local or in your startup script of your app

Source code

PCB components
Found the basic outline here so thanks for sharing mate!

THE PCB
On my github as usual.

SHUTDOWN SCRIPT


# External module imports                                                                                               
import RPi.GPIO as GPIO
import time, os

# Pin Definitons:  
buttonPin = 21


def my_callback_shutdown(channel):
    print ("Shut down!")
    os.system("sudo shutdown -h now")


# Pin Setup:           
GPIO.setmode(GPIO.BCM) # Broadcom pin-numbering scheme
GPIO.setup(buttonPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.add_event_detect(buttonPin, GPIO.FALLING, callback=my_callback_shutdown, bouncetime=300)


print("Waiting for shudown switch on GPIO%d" % (buttonPin))
try:
    while 1:
        time.sleep(10)

except KeyboardInterrupt: # If CTRL+C is pressed, exit cleanly:
    GPIO.cleanup() # cleanup all GPIO

LED BLINK
It's done in the project SNES Pi webserver check the file ledz.py.
There's an interresting trick to use the concurrent.futures functions to have the blink running on another thread. Have a peek.

Pictures

Pinout from Element14

//Circuit for my own version of a PowerBlock

Links

Helpful sources

Very nice tutorial on interrupt on Raspi with in RPi.GPIO

https://learn.sparkfun.com/tutorials/raspberry-gpio

Inspiration

All content on this site is shared under the MIT licence (do what u want, don't sue me, hat tip appreciated)
electrogeek.tokyo ~ Formerly known as Kalshagar.wikispaces.com and electrogeek.cc (AlanFromJapan [2009 - 2025])