Reading arduino data

Using Arduino Project Guidance
1

Ok so I am having some issues reading date sent from the Arduino via the serial port to a Linux (ubuntu) platform. I am using python3 on Linux to receive and display the data. Here is the python 3 code:

import serial
import sys

ser = serial.Serial(
        # Serial Port to read the data from
        port='/dev/ttyACM0',
 
        #Rate at which the information is shared to the communication channel
        baudrate = 9600,
   
        #Applying Parity Checking (none in this case)
        parity=serial.PARITY_NONE,
 
       # Pattern of Bits to be read
        stopbits=serial.STOPBITS_ONE,
     
        # Total number of bits to be read
        bytesize=serial.EIGHTBITS,
 
        # Number of serial commands to accept before timing out
        timeout=1
)
# Pause the program for 1 second to avoid overworking the serial port
while 1:
        x=ser.readline()
        data=ser.inWaiting
        print(x)

Here's the output. I don't understand the b. The \r\n I get, but not sure why I am getting that. I was expecting 23.4. I think there is a basic something I am not getting on serial readline(), like its reading bytes as an array and just displaying them as a string. But the b is still a mystery unless I have a serial parameter wrong.

b''
b''
b''
b'23.40\r\n'
b''
b''
b'23.40\r\n'
b''
b''
b'23.40\r\n'
b''

Here is the Arduino code. Basically the DHT22 example but I don't plug the sensor in so the only part of the code that executes is after the if data check.

/*
 * Created by ArduinoGetStarted.com
 *
 * This example code is in the public domain
 *
 * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-dht22
 */

#include "DHT.h"
#define DHT22_PIN 2

DHT dht22(DHT22_PIN, DHT22);

void setup() {
  Serial.begin(9600);
  dht22.begin(); // initialize the DHT22 sensor
}

void loop() {
  // wait a few seconds between measurements.
  delay(2000);

  // read humidity
  float humi  = dht22.readHumidity();
  // read temperature as Celsius
  float tempC = dht22.readTemperature();
  float tempCI =23.4;
  // read temperature as Fahrenheit
  float tempF = dht22.readTemperature(true);

  // check if any reads failed
  if (isnan(humi) || isnan(tempC) || isnan(tempF)) {
    // Serial.println("Failed to read from DHT22 sensor!");
    //Serial.write("\n");
    Serial.print(tempCI);
    Serial.print("\r\n");
  } else {
    Serial.print("DHT22# Humidity: ");
    Serial.print(humi);
    Serial.print("%");

    Serial.print("  |  "); 

    Serial.print("Temperature: ");
    Serial.print(tempC);
    Serial.print("°C ~ ");
    Serial.print(tempF);
    Serial.println("°F");
  }
}

When I capture the data in miniterm its fine so must be something in the python code.

Any help will be greatly appreciated. Thanks.

2

The b is Python telling you that is a bytes object and not a string. You wont be able to co.pare that with another string.

Try:

x=ser.readline().decode("utf_8")

3

If you don't need the "\r\n", why do you still sending it?

4

To put each tempCI on a new line. Otherwise they are all printed on one line. Just for show right not, not necessary at future implementations of the project.

5

Many thanks. Been banging my head against that for hours. I thought is was something like that, just not that familiar with serial coding.
Thanks again!!

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