Reading PushButton status with pyserial

Question

I'm trying to read the status of a PushButton with python via pyserial.

In the loop function of Arduino Uno I have this:

void loop() {

if(digitalRead(BUTTON) == HIGH){
Serial.print("E\n");
while(1){}
}

So, if my pushbutton is pressed, it will send this message "E" via serial and then it will enter in an infinite loop so that nothing else happens.

But I want to detect this message in the python code. So this is my python code:

import serial
import time

try:
   arduino = serial.Serial('/dev/ttyACM0', 9600)
except:
   print "Failed to connect on /dev/ttyACM0"


try:
   print arduino.readline()

   while True:
      if arduino.readline() == 'E':
        print("Detected!\n")

except:
   print ("Failed to read!")

The first print before the infinite While is working: it is printing in the ubuntu terminal "Program Initiated", which is a message that I'm sending in the void Setup function of Arduino.

Then, it gets stucked in the line:

 if arduino.readline() == 'E':

I mean, I press several times my pushbutton, and nothing is happening.

Any help? Thanks!

Answer 1

The string you are sending ("E\n") is not the same one you are checking for: 'E'.

You could, for example, strip newlines from the string:

if arduino.readline().strip() == 'E':