Python Raspberry Pi GPIO error

Question

I am running the following python script on my Raspberry Pi:

http://www.skpang.co.uk/dl/rfid.py

I've modified the script towards the end to access the GPIO pin 15 and turn it on and off. Here is my code at the bottom:

def example():

rfid = SL030()
fw = rfid.get_firmware()
print("RFID reader firmware:" + fw)
print()

GPIO.setmode(GPIO.BOARD)
GPIO.setup(15, GPIO.OUT)
GPIO.output(15,True)


while True:
    rfid.wait_tag()
    print("card present")

    if rfid.select_mifare():
        type = rfid.get_type()
        print("type:" + rfid.get_typename(type))

        id = rfid.get_uidstr()
        try:
            user = cards[id]
            print(user)
            #os.system("aplay " + user)
        except KeyError:
            print("Unknown card:" + id)

    rfid.wait_notag()
    print("card removed")
    print()

Problem i am facing is that although it operates pin 15, the script halts with the following error:

Traceback (most recent call last):
  File "./rfid.py", line 212, in <module>
    example()
  File "./rfid.py", line 182, in example
rfid.wait_tag()
  File "./rfid.py", line 45, in wait_tag
while not self.tag_present():
  File "./rfid.py", line 40, in tag_present
    return GPIO.input(CFG_TAG_DETECT) == False
    RPi.GPIO.InvalidChannelException: The channel sent is invalid on a Raspberry Pi

Any ideas what can be wrong?

Thanks

UPDATE

If i put the GPIO code just below the def example(): and above the rfid = SL030() like below, then it seems to work without error:

def example():

    GPIO.setmode(GPIO.BOARD)
    GPIO.setup(15, GPIO.OUT)
    GPIO.output(15,True)

    rfid = SL030()

*UPDATE - SOLUTION*

Thanks to André, i changed:

GPIO.setmode(GPIO.BOARD)

to: GPIO.setmode(GPIO.BCM)

and then changed the port to match the BCM port like this:

GPIO.setup(22, GPIO.OUT)
GPIO.output(22,True)

Community · Accepted Answer · 2017-04-13 12:32:45Z

6

From this question, it looks like there are two modes for GPIO : GPIO.BCM and GPIO.BOARD... try using the other one :

GPIO.setmode(GPIO.BCM)

edited Apr 13, 2017 at 12:32

CommunityBot

11 silver badge

answered Dec 8, 2013 at 21:54

user2629998

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3 Comments

John Over a year ago

perfect, i changed it to GPIO.BCM and its all working now. Only thing is that i needed the change the port number to match the BCM number which is 22

thommie Over a year ago

Thats odd, because board 15 is the same as bcm 22... ?

Simara Over a year ago

Yes, setting the right mode helps, especially with a cheatsheet like raspi.tv/download/RPi.GPIO-Cheat-Sheet.pdf there are other available.

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