(ValueError) Serial port response reading with python

Question

I am trying to read response of the serial port. (I am using a RFID module) Here is my code:

import serial
ser = serial.Serial()
ser.port = "/dev/ttyUSB0"
ser.baudrate = 9600
ser.timeout = 3
ser.open()
if ser.isOpen():
    ser.write("\xFF\x01\x03\x10\x02\x02\x18")
    print("command written")
while ser.isOpen():
    response = ser.read(5)
    print("trying to read")
    print(int(response,16))

At first I used directly print(response) and what I got was:

trying to read
�#��

Therefore I used print(int(response,16)) in order to convert response to integer and now I am getting error:

Traceback (most recent call last):
  File "serialread.py", line 13, in <module>
    print(int(response,16))
ValueError: invalid literal for int() with base 16: '\x94#\xdb\xff'

What should I do? I am pretty new to python and do not have any idea what the problem can be.

Burhan Khalid · Accepted Answer · 2012-06-19 14:09:19Z

1

Your string is already a hex literal:

>>> x = '\x94#\xdb\xff'
>>> x.encode('hex')
'9423dbff'
>>> int(x.encode('hex'),16)
2485378047L

answered Jun 19, 2012 at 14:09

Burhan Khalid

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3 Comments

Amadeus Over a year ago

Hmm.. Ok now I am able to print 2485378047. But I do not want to print it in this way. I want to print it as 94 db ff etc. How can I do it? Thank you for your help.

Amadeus Over a year ago

Also, now I did the required changes at my code and my current problem is: trying to read 2485378047 trying to read Traceback (most recent call last): File "serialread.py", line 15, in <module> print(int(response,16)) ValueError: invalid literal for int() with base 16: '' Sorry for spamming you with my beginner questions.

Burhan Khalid Over a year ago

You need to change print(int(response,16)) to print(response.encode('hex'))

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