Python serial.write() does not send serial data to Arduino

Question

I am writing a Python script, that sends a character to an Arduino and the Arduino prints the received character back. But in this case, the Arduino is always giving a garbage value. Also there is no error while executing the Python script.

I have checked multiple blogs, articles and tutorials and followed the exact steps, but I got no solution.

This is my Python script:

import serial
ser = serial.Serial("/dev/ttyACM0",9600)
ser.write('8')
read=ser.readline()
print(read)

This is the Arduino code:

int temp;
void setup() {
  Serial.begin(9600);
  temp=5;
}

void loop() {
  temp=Serial.read();
  Serial.println(temp);
  delay(1000);
}

Arduino always prints -1 in response.

gre_gor · Accepted Answer · 2017-09-07 13:13:04Z

2

Documentation on Serial.read():

Returns

the first byte of incoming serial data available (or -1 if no data is available) - int

So do as Ivan Sheigets suggested or

void setup() {
  Serial.begin(9600);
  Serial.print("You sent: ");
}

void loop() {
  int temp=Serial.read();
  if(temp>=0)
    Serial.print((char)temp);
}

Make sure to cast the incoming value to char (char)temp.

edited Sep 7, 2017 at 13:13

gre_gor

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answered Sep 6, 2017 at 18:03

Gruber

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Comments

gre_gor · Accepted Answer · 2017-09-07 13:08:12Z

1

You need to add Serial.available().

void loop() 
{
    if (Serial.available() > 0)
    {
      temp=Serial.read();
      Serial.print(" I received:");
      Serial.println(temp);
    }
}

edited Sep 7, 2017 at 13:08

gre_gor

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answered Sep 6, 2017 at 13:48

Ivan Sheihets

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