从 Python+Pyserial 向 Arduino 发送串行数据时出错

Question

For all this, I am using Windows 7, Python 2.7.3 and Pyserial 2.6. I am using COM6 for my Arduino.

I am trying to send data from a Python program, to the Arduino to read, and it keeps returning a "SerialException error.

Here is the Python code:

import serial
import time
ser = serial.Serial('COM6', 9600, timeout=0)
var = raw_input("Enter something: ")
ser.write(var)
while 1:
    try:
        print ser.readline()
        time.sleep(1)
    except ser.SerialTimeoutException:
        print('Data could not be read')

Here is the Arduino code:

int incomingByte = 0;

void setup(){
// Open serial connection.
Serial.begin(9600);

}

void loop(){
if (Serial.available() > 0) {
 // read the incoming byte:
 incomingByte = Serial.read();

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

}

Here is the error I am getting in Python when I run the script:

Traceback (most recent call last):
  File "C:/Users/admin/Desktop/test", line 3, in <module>
    ser = serial.Serial('COM6', 9600, timeout=0)
  File "C:\Python27\lib\site-packages\serial\serialwin32.py", line 34, in __init__
    SerialBase.__init__(self, *args, **kwargs)
  File "C:\Python27\lib\site-packages\serial\serialutil.py", line 261, in __init__
    self.open()
  File "C:\Python27\lib\site-packages\serial\serialwin32.py", line 62, in open
    raise SerialException("could not open port %s: %s" % (self.portstr, ctypes.WinError()))
SerialException: could not open port COM6: [Error 5] Access is denied.

How can I resolve that error? Python will read from the Arduino just fine, but not write to it.

Answer 1

Besides ensuring that the port is closed, a couple of additional things to note...

• Data sent using PySerial can only be of type byte (or bytestream for more than 1 byte data). You can't send user input as it is.

• flush() the data after writing