Using Callbacks

Below is a simple programming example that illustrates how to use callbacks to monitor an analog and digital input.

""""
This example illustrates using callbacks for digital input, and analog input.
Monitor the current analog input and digital input of 2 pins.
"""

import signal
import sys

from PyMata.pymata import PyMata


# Pin definitions

# Digital Input Pin
PUSH_BUTTON = 12

# Analog Input Pin - A2
POTENTIOMETER = 2

# Indices for data passed to callback function

PIN_MODE = 0  # This is the PyMata Pin MODE = ANALOG = 2 and DIGITAL = 0x20:
PIN_NUMBER = 1
DATA_VALUE = 2


# Control-C signal handler to suppress exceptions if user presses Control C
# This is totally optional.

# noinspection PyUnusedLocal
def signal_handler(sig, frame):
    print('You pressed Ctrl+C!!!!')
    if board is not None:
        board.reset()
    sys.exit(0)


# data change callback functions
def cb_potentiometer(data):
    print("Analog Data: Pin Mode - ", data[PIN_MODE], " Pin Number -", data[PIN_NUMBER], " Data Value -  ",
          data[DATA_VALUE])


def cb_push_button(data):
    print("Digital Data: Pin Mode - ", data[PIN_MODE], " Pin Number -", data[PIN_NUMBER], " Data Value -  ",
          data[DATA_VALUE])


signal.signal(signal.SIGINT, signal_handler)  # Instantiate PyMata
board = PyMata("/dev/ttyACM1")

# set up pin modes for both pins with callbacks for each
board.set_pin_mode(PUSH_BUTTON, board.INPUT, board.DIGITAL, cb_push_button)
board.set_pin_mode(POTENTIOMETER, board.INPUT, board.ANALOG,
                   cb_potentiometer)  

# A forever loop until user presses Control-C
while 1:
    pass