While statement checking for button press while accepting raw input

Question

I have a while statement running and checking if my button (on a gpio) is pressed and once it is I print something. I would like to add some shell commands like exit, etc... How can i have the while statement running while also accepting raw input and run different things depending on what's typed? (ex. check for button press in background but have raw input accept the word exit and close the program)

--Thanks

#--------------------------
#SORRY FOR HOW SLOPPY IT IS
#--------------------------


import RPi.GPIO as GPIO
import time
import os
import sys
sys.path.append('/usr/local/lib/python2.7/dist-packages')

#Library that allows me to print to my printer
from escpos import *

#To get the weather
import pywapi


import string

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

button = 26
green = 4
yellow = 18
GPIO.setup(green, GPIO.OUT)
GPIO.setup(yellow, GPIO.OUT)
GPIO.setup(button, GPIO.IN, GPIO.PUD_UP)

GPIO.output(green, 1)
GPIO.output(yellow, 0)

print("Waiting for button press...")




#When the button is pressed begin the weather fetching and printing
def buttonPress(button):
    GPIO.output(green, 0)
    GPIO.output(yellow, 1)
    print("Printing...")
    weather_com_result = pywapi.get_weather_from_weather_com('CAXX2088')
    temp = (weather_com_result['current_conditions']['temperature'])
    text = string.lower(weather_com_result['current_conditions']['text'])
    precip0 = (weather_com_result['forecasts'][0]['day']['chance_precip'])
    precip1 = (weather_com_result['forecasts'][1]['day']['chance_precip'])
    precip_date1 = (weather_com_result['forecasts'][1]['date'])
    high = (weather_com_result['forecasts'][1]['high'])
    low = (weather_com_result['forecasts'][1]['low'])
    Epson = printer.Usb(0x04b8,0x0202)

    Epson.set(align="CENTER")
    Epson.set(bold=True)
    Epson.set(size="2x")
    Epson.text("Current Weather\n\n")

    Epson.set(size='normal')
    Epson.set(bold=False)

    Epson.text(string.capwords(text))

    Epson.text(" and "+temp)

    Epson.text("C\n")

    Epson.text("POP: " + precip0 + "%\n\n")

    Epson.set(bold=True)

    Epson.set(size="2x")

    Epson.text("Forecast For " + precip_date1 + "\n\n")

    Epson.set(size='normal')

    Epson.set(bold=False)

    Epson.text("POP: " + precip1 + "\n")
    Epson.text("High: " + high + "C  Low: "+ low +"C\n")
    Epson.cut()
    time.sleep(3)
    print("Printed.")

    #A loop that flashes a green light until the printer is ready for another print

    waittime=0

    while waittime<11:
        GPIO.output(green, 1)
        GPIO.output(yellow, 0)

        time.sleep(1)

        GPIO.output(green, 0)
        GPIO.output(yellow, 0)
        time.sleep(1)

        waittime += 2

    GPIO.output(green, 1)
    print("Waiting for button press...")



#Where I want to be able to input the command
#Also i know that this isnt a loop and will only happen once (i think) but i think i can manage to turn it into a loop later on
command = raw_input(": ")

GPIO.add_event_detect(button, GPIO.RISING,callback=buttonPress)

if command == "exit":
    GPIO.cleanup()
    sys.exit()

Answer 1

Depending on how your circuit is wired you should use

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)

inputPin = "YOUR_PIN_GOES_HERE"
GPIO.setup(inputPin,GPIO.IN,pull_up_down=GPIO.PUD_UP)

def buttonPress(channel):
     #stuff

def buttonRelease(channel):
     #stuff


GPIO.add_event_detect(channel,GPIO.RISING,callback=buttonPress)
#OR
GPIO.add_event_detect(channel,GPIO.FALLING,callback=buttonRelease)

while(1):
      keypressed = raw_input('Press q to quit: ')
      if keypressed == 'q':
           break
      elif keypressed == 'SOME OTHER KEY':
           #code for some other thing
      else
           print("Unknown input")

These are events that will be trigged where there is a change on your input pin. Your raw_input can still handle whatver code you want because the event loop is running in the background.

Pulled from here

Edits: put the event defs above event declaration because I am teh dumb

While(1)'s are ugly. For the sake of staying a loop this should suffice though. Essentially this will run the keyboard input loop until you hit q. Use the elifs to handle other inputs. The else will capture unknown input and provide feedback. The break statment will boot the program out of the while loop and will reach the end of code and terminate.

Should you feel fancy and want to handle a lot of input I would look to use what other languages have a switch statement to clean up a bunch of elifs

Oh and standard warranty applies, I may have missed a tab or : here and there.

Answer 2

Your Python module will offer GPIO callbacks. Generally you specify

• a GPIO
• whether you are interested in rising edges (0->1), falling edges (1->0), or both edges
• and a function to be called when the event happens

The specified function will be called asynchronously to the main thread, i.e. it will still be called even if the main thread is waiting in a raw_input.

Generally you would use global variables to pass state information between the callback and main thread.