I am a complete newbie with Raspberry Pi and any type of hardware prototyping. I have been trying to get a Parallax RFID working with my Pi 3.

I currently have it wired to the GPIO using BCM and the following pins

VCC -> 5V

/Enable -> Pin 4

SOUT -> Pin 15


I then use a python script:

import RPi.GPIO as GPIO
import serial

ENABLE_PIN  = 4              # The BCM pin number corresponding to GPIO1
SERIAL_PORT = '/dev/ttyAMA0'  # The location of our serial port.  This may
                          # vary depending on OS version.

def validate_rfid(code):
# A valid code will be 12 characters long with the first char being
# a line feed and the last c har being a carriage return.

s = code.decode("ascii")
if (len(s) == 12) and (s[0] == "\n") and (s[11] == "\r"):
    # We matched a valid code.  Strip off the "\n" and "\r" and just
    # return the RFID code.
    return s[1:-1]
    # We didn't match a valid code, so return False.
    return False

def main():
# Initialize the Raspberry Pi by quashing any warnings and telling it
# we're going to use the BCM pin numbering scheme.

# This pin corresponds to GPIO1, which we'll use to turn the RFID
# reader on and off with.

# Setting the pin to LOW will turn the reader on.  You should notice
# the green LED light on the reader turn red if successfully enabled.

print("Enabling RFID reader...\n")

# Set up the serial port as per the Parallax reader's datasheet.
ser = serial.Serial(baudrate = 2400,
                    bytesize = serial.EIGHTBITS,
                    parity   = serial.PARITY_NONE,
                    port     = SERIAL_PORT,
                    stopbits = serial.STOPBITS_ONE,
                    timeout  = 1)

# Wrap everything in a try block to catch any exceptions.
    # Loop forever, or until CTRL-C is pressed.

    while 1:
        # Read in 12 bytes from the serial port.
        data = ser.read(12)
        # Attempt to validate the data we just read.
        code = validate_rfid(data)

        # If validate_rfid() returned a code, display it.
        if code:
            print("Read RFID code: " + code);
except Exception:
    # If we caught an exception, then disable the reader by setting
    # the pin to HIGH, then exit.
    print ("Couldn't do it: %s" % e)
    print("Disabling RFID reader...")

if __name__ == "__main__":

The script runs and shows "Enabling RFID reader..." and then nothing when I pass chips in front of the reader.

I have ensured that Serial is enabled in config and I have tried both /dev/ttyAMA0 and /dev/ttyS0 (as I have read that ttyS0 is for Pi 3s)

I have tried multiple RFID cards that I got from Parallax for testing, and a couple cards from around the office that I know work with other readers.

I am at a loss on where to go from here. Any help or pointers would be greatly appreciated.

UPDATE: I found information about changing the /boot/cmdline.txt to remove "console=serial0,115200" so I did. This did not change the results.

1 Answer 1


I know that this is an old post, but I will try to answer anyways, as I am doing the exact same setup at my job at the moment.

Have you enabled UART in the config.txt?

sudo nano /boot/config.txt

Then at the bottom, add this line:


Then try to reboot and see if that works.

Context: For some reason, UART is disabled as default in the newer versions of Raspbian.

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