1

I am trying to send messages between python and the arduino via serial port. I am successful going in the Arduino->python direction with this code:

The python:

import termios, fcntl, sys, os, serial, time, smtplib
ser = serial.Serial('/dev/tty.usbserial-AD02AY8A', 9600, writeTimeout = 0)
while 1:
    message = ser.readline()
    print(message)

The Arduino:

// the setup routine runs once when you press reset:
void setup() {
// initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
  Serial.write('1');
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin 0:
  Serial.println("BOBBY");
  delay(1);        // delay in between reads for stability
}

In this case, I can view the serial port from arduino and the "screen command" on terminal, as well as through the python reprinting "BOBBY".

When I try to send the message from python, it never shows up on the terminal screen or in the Arduino serial port.

Here's the python code that doesn't work. The arduino code shouldn't matter for this one, as I am just monitoring the serial port. 

import termios, fcntl, sys, os, serial, time, smtplib
ser = serial.Serial('/dev/tty.usbserial-AD02AY8A', 9600, writeTimeout = 0)
time.sleep(2)

while 1:
  try:
    ser.write('1')
  except: # catch *all* exceptions
    print(e)
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4 Answers 4

Reset to default
3

From your code I think it is safe to assume that you are using the USB serial interface on the Arduino. If that is the case, the Arduino is designed to reset everytime a serial connection is made over the USB interface.

This will keep it from receiving transmissions. You can test this by trying to send serial using the python command line instead of a file.

If that works, you have two options,

1) Write in a time.sleep(2) line after you open the port to give the Arduino time to reboot. -or-

2) install a 10 micro farad capacitor between the ground pin and reset on the Arduino board.

This will prevent it from going into reset while the serial port connects, and can be easily removed later when you use the board for another project.

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1 Comment

The delay worked for me. Alternatively, I added a line in setup() in Arduino code to send a byte and waited for that in python.
1

I tried Arduino code with an LED to see whether anything was being written to the port. Surely enough, it was writing this whole time. But using the serial monitor in Arduino did not display the content.

Here is the Arduino code:

int ledPin = 13;  
// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 9600 bits per second:
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

// the loop routine runs over and over again forever:
void loop() {

   if (Serial.available()>0){
       Serial.read();
       for (int i = 0; i < 5; i++){

        // read the input on analog pin 0:
        digitalWrite(ledPin, HIGH);   // turn the LED on (HIGH is the voltage level)
        delay(50);               // wait for a second
        digitalWrite(ledPin, LOW);   // turn the LED on (HIGH is the voltage level)
        delay(50);   
        } 
       }
      }
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1 Comment

I guess if you are not examining the value, it doesn't matter if it is encoded or not.... but when I send data over serial I always encode to ascii so that I don't have issues...my answer actually probably encodes to utf-8 in most python versions.
-1

please try to add print(ser.write('1')) like this.

while 1:
  try:
    ser.write('1')
   print(ser.write('1'))
  except: # catch *all* exceptions
    print(e)
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Comments

-2

Kind of a shot in the dark, but looking at your print statements, this is python 3.

You will need to encode all the transfer to byte strings like this:

ser.write('1'.encode())
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