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I want to send 4 float numbers from a python code to an Arduino, I was trying to send it via serial and i have some problems

here is my python code:

import time
import serial
import struct

data = serial.Serial('COM6', 9600, timeout=1)
time.sleep(1)

while True:
   a = str(47.256*1000)   
   data.write(a.encode())

here is my arduino code :



String msg;

void setup()
{   
  Serial.begin(9600);
  pinMode(13, OUTPUT);       
}


void loop()
{

  if(Serial.available()) {
    msg = Serial.readString();
  }

  if(msg.toInt()>30){
    digitalWrite(13,1);
  }
}

end of code

thanks in advance

my problem is that it does not work (Led does not turns on while I send data from the python code in a while loop if I removed the while and made it send data 1 time it works (led turns on) any ideas why this could be happening

  • 2
    "I can't do it" is not a good problem description. What exactly is your problem in writing the code? What exactly did you try? Please add this information to the question by editing it – chrisl Mar 21 at 10:18
  • 1
    When you say it does not work, what do you mean? Exactly what happens? What is in your init () method? Are you setting up Serial? Are you setting the LED for output? Please submit the entire code. – GMc Mar 23 at 10:59
  • 1
    That while loop in the python code is going to send that number over and over really really fast. I wonder if you shouldn't slow that down just a little. Put a sleep call in that while loop. – Delta_G Mar 23 at 16:48
0

It would be easier if you used Arduino <--> Python compatible libraries to ensure the communication between the two is robust and reliable. An example of such libraries would be pySerialTransfer and SerialTransfer.h.

pySerialTransfer is pip-installable and cross-platform compatible. SerialTransfer.h runs on the Arduino platform and can be installed through the Arduino IDE's Libraries Manager.

Both of these libraries have highly efficient and robust packetizing/parsing algorithms with easy to use APIs.

Example Python Script:

import time
from pySerialTransfer import pySerialTransfer as txfer


if __name__ == '__main__':
    try:
        link = txfer.SerialTransfer('COM17')

        link.open()
        time.sleep(2) # allow some time for the Arduino to completely reset

        while True:
            send_size = 0

            ###################################################################
            # Send a list
            ###################################################################
            list_ = [1, 3]
            list_size = link.tx_obj(list_)
            send_size += list_size

            ###################################################################
            # Send a string
            ###################################################################
            str_ = 'hello'
            str_size = link.tx_obj(str_, send_size) - send_size
            send_size += str_size

            ###################################################################
            # Send a float
            ###################################################################
            float_ = 5.234
            float_size = link.tx_obj(float_, send_size) - send_size
            send_size += float_size

            ###################################################################
            # Transmit all the data to send in a single packet
            ###################################################################
            link.send(send_size)

            ###################################################################
            # Wait for a response and report any errors while receiving packets
            ###################################################################
            while not link.available():
                if link.status < 0:
                    if link.status == -1:
                        print('ERROR: CRC_ERROR')
                    elif link.status == -2:
                        print('ERROR: PAYLOAD_ERROR')
                    elif link.status == -3:
                        print('ERROR: STOP_BYTE_ERROR')

            ###################################################################
            # Parse response list
            ###################################################################
            rec_list_  = link.rx_obj(obj_type=type(list_),
                                     obj_byte_size=list_size,
                                     list_format='i')

            ###################################################################
            # Parse response string
            ###################################################################
            rec_str_   = link.rx_obj(obj_type=type(str_),
                                     obj_byte_size=str_size,
                                     start_pos=list_size)

            ###################################################################
            # Parse response float
            ###################################################################
            rec_float_ = link.rx_obj(obj_type=type(float_),
                                     obj_byte_size=float_size,
                                     start_pos=(list_size + str_size))

            ###################################################################
            # Display the received data
            ###################################################################
            print('SENT: {} {} {}'.format(list_, str_, float_))
            print('RCVD: {} {} {}'.format(rec_list_, rec_str_, rec_float_))
            print(' ')

    except KeyboardInterrupt:
        link.close()

    except:
        import traceback
        traceback.print_exc()

        link.close()

Example Arduino Sketch:

#include "SerialTransfer.h"


SerialTransfer myTransfer;


void setup()
{
  Serial.begin(115200);
  myTransfer.begin(Serial);
}


void loop()
{
  if(myTransfer.available())
  {
    // send all received data back to Python
    for(uint16_t i=0; i < myTransfer.bytesRead; i++)
      myTransfer.txBuff[i] = myTransfer.rxBuff[i];

    myTransfer.sendData(myTransfer.bytesRead);
  }
}

Note that you can send more than just individual chars with these libraries. It is possible to transfer floats, ints, bytes, arrays, and even structs (or any combination of the like) within your program using the libraries! See the examples in SerialTransfer.h for more info

For theory behind robust serial communication, check out the tutorials Serial Input Basics and Serial Input Advanced.

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