How to control the GPIO?

Hardware and peripherals
10

I implemented a Python wrapper for the GPIOs. One thing to observe is to make a call to seek(0), otherwiese the pins will not show the change in state.

GPIO class:

import os
from subprocess import run
from time import sleep

class GPIO:
    """ class to initialize and switch GPIO pins """
    def __init__(self, gpio_pin):
        """ :param gpio_pin: either a string of the form "GPIO3_D5" where 3 is the bank number  and D5 the address name, or, an integer """

        if type(gpio_pin) == str:
            if not self.parse_gpio_pin(gpio_pin):
                raise ValueError
        elif type(gpio_pin) == int:
            self.pin_number = str(gpio_pin)
        else:
            raise ValueError

        self.pin_dir = "gpio" + self.pin_number  # /sys/class/gpio pin directory name
        self.pin = None  # file descriptor for pin

    def parse_gpio_pin(self, gpio_pin):
         """ parses the input parameter """
        parts = gpio_pin.split('_')
        if len(parts) == 2 and len(parts[0]) == 5 and len(parts[1]) == 2:
            try:
                bank = int(parts[0][4])
            except ValueError:
                return False

            address1_coding = {'A': 0, 'B': 1, 'C': 2, 'D': 3}
            try:
                address1 = address1_coding[parts[1][0]]
            except KeyError:
                return False

            try:
                address2 = int(parts[1][1])
            except ValueError:
                return False

            self.pin_number = str(bank * 32 + address1 * 8 + address2)
            return True

        else:
            return False

    def configure(self):
        """ configure pin for output """
        if not os.path.exists('/sys/class/gpio/' + self.pin_dir):
            subprocess.run('echo ' + self.pin_number + ' > ' + '/sys/class/gpio/export', shell=True)
        subprocess.run('echo out' + ' > ' + '/sys/class/gpio/' + self.pin_dir + '/direction', shell=True)

    def open(self):
        """ open pin directory for writing """
        self.pin = open('/sys/class/gpio/' + self.pin_dir + '/value', 'w')

    def switch(self, on):
        """ function to set pin high or low"""
        if on is True:
            self.pin.write('1')
        else:
            self.pin.write('0')
        # writing becomes effective only after a seek(0):
        self.pin.seek(0)

    def close(self):
        """ close pin directory """
        if self.pin is not None and not self.pin.closed:
            self.pin.close()

    def __del__(self):
        """ automatic closing on object deletion """
        self.close()

Usage:

# test with pin for red on-board LED
gpio = GPIO("GPIO3_D5")
gpio.configure()
gpio.open()

for i in range(10):
    gpio.switch(True)
    sleep(1)
    gpio.switch(False)
    sleep(1)
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