CODEWITHSUNDEEP
pythonpython-3.xarduinoraspberry-piserial-port
Michael S
Michael S

Reputation: 104

Serial communication error between Arduino and Python

I want to send values from a Python program on a Raspberry Pi to an Arduino. My RPi program looks like that:

import time, serial
time.sleep(3)
ser = serial.Serial('/dev/ttyACM0', 9600)
ser.write(b'5')

My Arduino program:

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

void loop() {
    char inByte = ' ';
    if(Serial.available()) {         
        inByte = Serial.read();
        Serial.println(inByte);
    } 
    delay(100)
}

My problem is that when I run the program in Python and afterwards open the serial monitor in the Arduino IDE, it only shows "ready", but not the sent value. If I want to have the monitor open at the same time as the program, there is the error:

Device or resource busy: '/dev/ttyACM0'

I am using Python 3.6 by the way.

I am sorry if this is an easy error, but I am very new to serial and Arduino.

Upvotes: 0

Views: 2023

Answers (1)

MihanEntalpo
MihanEntalpo

Reputation: 2072

You can connect to your Arduino serial port from only one application at a time. When you are connected to it via Serial port Monitor, Python couldn't connect to it.

You have two variants of solution:

  1. Use serial sniffer instead of Arduino IDE's Serial Monitor. There are another answered question on this topic: https://unix.stackexchange.com/questions/12359/how-can-i-monitor-serial-port-traffic

  2. Don't use any serial monitor, use Python! You can just continiualy read from serial, and print what have been received, something like this:

    import time, serial
time.sleep(3)
ser = serial.Serial('/dev/ttyACM0', 9600)
# Write your data:
ser.write(b'5')

# Infinite loop to read data back:
while True:
    try:
        # get the amount of bytes available at the input queue
        bytesToRead = ser.inWaiting() 
    if bytesToRead:
        # read the bytes and print it out:
        line = ser.read(bytesToRead) 
        print("Output: " + line.strip())
except IOError:        
    raise IOError()

Upvotes: 0

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