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Raspberry Pi + FLIRC + Apple Remote for Alps Motorized Volume Control


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FLIRC is a wonderful thing. 


USB DACs disable the volume control on Macs. This is sensible from a perfectionist perspective but obnoxious when it adds to the remote control garden. I decided to hijack 3 of the 7 buttons on an Apple Remote and hook up an Alps motorized potentiometer and a mute circuit. It's in a gutted an old Advent radio with the LEDs wired to show activity.


Aside from FLIRC, the big find was pygame, which allowed me to capture the keystrokes without fail. With a tiny shell script, the simple code below runs beautifully as an appliance on powerup without a display or keyboard or network. The added circuitry is just 2 L272M power opamps, a 2N3906 transistor and one J111 J-FET for each channel to be muted. The circuit diagram is scattered on multiple scraps of paper but if you contact me I'll maybe clean it up to post.



import RPi.GPIO as GPIO
import time
import pygame
screen = pygame.display.set_mode((100, 100))
# to use Raspberry Pi board pin numbers
# setup Volume UP / DOWN pins with LEDs OFF
GPIO.setup(16, GPIO.OUT)
GPIO.output(16, GPIO.HIGH)
GPIO.setup(18, GPIO.OUT)
GPIO.output(18, GPIO.HIGH)
# setup Mute to be Off with LED OFF
GPIO.setup(22, GPIO.OUT)
GPIO.output(22, GPIO.LOW)
MUTED = False
def pulse(pin):
        GPIO.output(pin, GPIO.LOW)
        GPIO.output(pin, GPIO.HIGH)
#    time.sleep(1)
        # m
        for event in pygame.event.get():
            if event.type == pygame.KEYDOWN and event.key <= 256:
                print event.key, chr(event.key)
                if event.key == 117:
                elif event.key == 110:
                elif (event.key == 50) & MUTED:
                    GPIO.output(22, GPIO.LOW)
                    MUTED = False
                elif (event.key == 50) & (MUTED == False):
                    GPIO.output(22, GPIO.HIGH)
                    MUTED = True
                elif event.key == 27:
                    raise NameError('Quit')
    except NameError:
        print "    Normal exit"


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