Reading more than two Arduino sensors

Question

For a university project, I need to write a python script that uses the data of some Arduino ultrasonic sensors. I managed to glue together a way to read one using tutorials found on google, but I don't really know if it's applicable to more of them.

Here's the Arduino code:

int trigPin = 11;    // Trigger
int echoPin = 12;    // Echo
long duration, cm, inches;

void setup() {
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(5);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);

  cm = (duration/2) / 29.1;     // Divide by 29.1 or multiply by 0.0343

  Serial.print(cm);
  Serial.println();

  delay(250);
}

Just a basic ultrasonic sensor code, easy to add more sensors if needed.

And here is the python code, where the problem lies.

import serial
import time

ser = serial.Serial('COM7', 9800)
time.sleep(2)

while True:
    line = ser.readline()   # read a byte
    if line:
        string = line.decode()  # convert the byte string to a unicode string
        num = int(string) # convert the unicode string to an int
        print(num)

ser.close()

I'm going tp admit that I really get 100% how the python script is reading the serial output from the Arduino, but I tested it and it worked.

My question is, can this method be used with more than one sensor, and if it can, how can I implement it?

Answer 1

Yes you can - I've run 5 ultrasonic sensors on an Arduino transmitting the results over serial to a python program.

You can either read all the distances at the same time and send them in a single string with a separator. Eg. "12:23:45”. In python use string.split(':') to separate into individual values.

Or send them one at a time with an identifier (useful if sensors are read at different rates). Eg "dist1:12" and "dist2:23" and use the same split() function to separate the identifier and the value.