Serial Communication between Arduino and Python, issue of using hexidecimal values

问题

I am attempting to start a motor from the computer by code in Python 3.4, using pySerial to communicate to an Arduino Uno. I have packed the value I am sending to hexidecimal, so I only have one byte at a time, but am having a problem getting the correct number on the Arduino side as I am sending on the Python side.

PYTHON CODE:

import serial 
import struct


ser = serial.Serial(
    port ='COM4', 
    baudrate = 9600, 
    parity = serial.PARITY_ODD, 
    stopbits = serial.STOPBITS_TWO, 
    bytesize = serial.EIGHTBITS
    )

#ser.open()     #opens port 
ser.isOpen()    #returns true?


motorState = 0
wristBend = 'Left'

while True:
    #need to create options to send to arduino

    if wristBend == 'Left':
        motorState = 2
    elif wristBend == 'Right':
        motorState = 3
    else:
        motorState = 1

    motorChar = struct.pack('<B', motorState)          #returns the value as a character interger
    #motorChar = str(hex(motorState))

    print(motorChar)
    ser.write(motorChar)
    print(ser.read())
    break

ARDUINO CODE:

int motorPinLeft = 10;
int motorPinRight = 11; 
int motorSpeedLeft = 0;
int motorSpeedRight = 0;


void setup() {
  pinMode(motorPinLeft, OUTPUT);
  pinMode(motorPinRight, OUTPUT);
  Serial.begin(9600);
  while(!Serial); //waits for arduino to be ready, not neaded for duo
  Serial.println("Speed 0 - 255");
}

void loop() 
{
  if (Serial.available())
  {
    int ch = Serial.read();

      switch (ch)
      {
        case 1:
          motorSpeedLeft = 0;
          motorSpeedRight = 0;
          break;
        case 2:
          motorSpeedLeft = 127;
          motorSpeedRight = 0;
          break;
        case 3:
          motorSpeedLeft = 0;
          motorSpeedRight = 127;
          break;

      }

      Serial.write(ch);

      analogWrite(motorPinLeft, motorSpeedLeft);
      analogWrite(motorPinRight, motorSpeedRight);

      delay(2500);     //wait for 2.5 seconds to make the motor vibrate
      motorSpeedRight = 0;
      motorSpeedLeft = 0;

      analogWrite(motorPinLeft, motorSpeedLeft);
      analogWrite(motorPinRight, motorSpeedRight);

Not only is nothing communicating with my circuit, but the output from my python code, where I print what is being sent to the Arduino and what is being sent from the Arduino is this:

b'\x02'
b'S'

If I change a switch case code to 83 (the ASCII code of S), or change the type of the variable to byte, int, uint8_t, I get the exact same output. What am I doing wrong here? Sorry if it is sort of obvious, I'm fairly new to python and arduino. Thanks in advance for any help!

回答1:

its not hard here is a simple example, its usually a good idea to start simple and then increase the functionality to what you want.

test_serial.py

import serial
ser = serial.Serial("COM4",timeout=5) # everything else is default
ser.write("\x45")
print "RECIEVED BACK:",repr(ser.read(5000))

test_serial.ino

int incomingByte = 0;   // for incoming serial data

void setup() {
        Serial.begin(9600);     // opens serial port, sets data rate to 9600 bps
}

void loop() {

        // send data only when you receive data:
        if (Serial.available() > 0) {
                // read the incoming byte:
                incomingByte = Serial.read();

                // say what you got:
                Serial.print("I received: ");
                Serial.println(incomingByte, DEC);
        }
}

来源：https://stackoverflow.com/questions/30335918/serial-communication-between-arduino-and-python-issue-of-using-hexidecimal-valu

标签

python

arduino

pyserial

serial-communication