Robust Arduino-Python Serial Communication

Question

I'm working on project where python sends motor commands to an Arduino Mega via USB. I have been playing with several variations of how to make the code robust so that the python program waits until the arduino is ready to receive. This is a super basic version for the question.

What is wrong is that the arduino println is sending the value back successfully to be read in the serial monitor in the arduino IDE. But the python is not reading it successfully to print a value to the command line.

What is wrong with my python read code?

Arduino

//++++++++++++++++++++Initializations+++++++++++++++++++++
int command = 0;
int control = 0;
boolean newInput = 0;
int myCount = 0;

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

void setup() {
  Serial.begin(9600);                    // set the baud rate
  Serial.println(1);                     // initial "ready" signal
}

void loop() {
   // read sent command and return it
    if(Serial.available() > 0){         // only send data back if data has been sent
      command = Serial.read();
      delay(10);

      Serial.println(1);                // send "ready" signal
      delay (50);                       //alternatively Serial.flush();
      myCount++;

    } 

}

Here is the condensed version of my program that highlights the issue.

Python

import serial
ser = serial.Serial('/dev/ttyACM0', 9600, timeout = 1)
import time

controlBit = True
n = 0
charsWait = 0   #chars waiting from arduino

print "Starting up"
connected = False

while True:
    n = n+1
    print n
    print "Writing"
    ser.write(str(2))
    time.sleep(1)
    while True:
        try:
            print "reading"
            charsWait = ser.readline()
            time.sleep(1)
            print "   = value recieved", charsWait 
            break
        except:
            pass
    print "restart"
    ser.flush() #flush the buffer

Raj Mehta Raj Mehta · Accepted Answer · 2021-02-24T17:57:09

<pre>Arduino code:
    //++++++++++++++++++++Initializations+++++++++++++++++++++
    int command = 0;
    int control = 0;
    boolean newInput = 0;
    int myCount = 0;
    
    //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    
    void setup() {
      Serial.begin(9600);                    # set the baud rate
      Serial.println("1");                    # initial "ready" signal
    }
    
    void loop() 
    {
       # read sent command and return it
        if(Serial.available() > 0)
        {
          command = Serial.read();
          Serial.println(command);                
        } 
    }
    
    
#Python Code for is waiting for Arduino listening state.

    import serial
    ser = serial.Serial('/dev/ttyACM0', 9600, timeout = 1)
    
    import time
    
    controlBit = True
    n = 0
    charsWait = 0   #chars waiting from Arduino
    
    print "Starting up"
    connected = False
    
    while True:
        charsWait = ser.read()   #ser.read data in ASCII
        print "   = value recieved", charsWait 
        if charsWait == 49:      #ASCII of 1=49**strong text**
             while True:
                 ser.write("As per you")

#means when Arduino setup is runs (time of initialization of Arduino) at time Arduino send "1" python is waiting to receive "1" after 1 they can work.

Robust Arduino-Python Serial Communication

1 Answers