Question

Create a code where you click on the appropriate buttons on your Python GUI and it turns on and off the corresponding LEDs for Arduino, please.

Answer 1

Here you are not only going to find code but a depp discussion of circuit and its connection along with Python Code.

Digital inputs can have only two possible values. In a circuit, each of these values is represented by a different voltage. The table below shows the digital input representation for a standard Arduino Uno board:

Value	Level	Voltage
0	Low	0V
1	High	5V

To control the LED, we’ll use a push button to send digital input values to the Arduino. The button should send 0V to the board when it’s released and 5V to the board when it’s pressed. The figure below shows how to connect the button to the Arduino board:

We may notice that the LED is connected to the Arduino on digital pin 13, just like before. Digital pin 10 is used as a digital input. To connect the push button, you have to use the 10 KOhm resistor, which acts as a pull down in this circuit. A pull down resistor ensures that the digital input gets 0V when the button is released.

When we release the button, we open the connection between the two wires on the button. Since there’s no current flowing through the resistor, pin 10 just connects to the ground (GND). The digital input gets 0V, which represents the 0 (or low) state. When you press the button, you apply 5V to both the resistor and the digital input. A current flows through the resistor and the digital input gets 5V, which represents the 1 (or high) state.

We can use a breadboard to assemble the above circuit as well:

Now that you’ve assembled the circuit, you have to run a program on the PC to control it using Firmata. This program will turn on the LED, based on the state of the push button:

import pyfirmata
 2 import time
 3 
 4 board = pyfirmata.Arduino('/dev/ttyACM0')
 5 
 6 it = pyfirmata.util.Iterator(board)
 7 it.start()
 8 
 9 board.digital[10].mode = pyfirmata.INPUT
10 
11 while True:
12     sw = board.digital[10].read()
13     if sw is True:
14         board.digital[13].write(1)
15     else:
16         board.digital[13].write(0)
17     time.sleep(0.1)

• Lines 1 and 2 import pyfirmata and time.
• Line 4 uses pyfirmata.Arduino() to set the connection with the Arduino board.
• Line 6 assigns an iterator that will be used to read the status of the inputs of the circuit.
• Line 7 starts the iterator, which keeps a loop running in parallel with your main code. The loop executes board.iterate() to update the input values obtained from the Arduino board.
• Line 9 sets pin 10 as a digital input with pyfirmata.INPUT. This is necessary since the default configuration is to use digital pins as outputs.
• Line 11 starts an infinite while loop. This loop reads the status of the input pin, stores it in sw, and uses this value to turn the LED on or off by changing the value of pin 13.
• Line 17 waits 0.1 seconds between iterations of the while loop. This isn’t strictly necessary, but it’s a nice trick to avoid overloading the CPU, which reaches 100% load when there isn’t a wait command in the loop.