I am currently trying to follow this tutorial. I keep running into errors for the RPi part. I have received several error related to SPI. I removed SPI from my blacklist and followed the instructions from a question asked on StackExchange to get to my current problem. The python code given in the tutorial imports the nrf24 library. I receive this error when I run (from tutorial):

/home/pi/nrf24pihub/nrf24.py:374: RuntimeWarning: This channel is already in use, >continuing anyway. Use GPIO.setwarnings(False) to disable warnings.

GPIO.setup(self.irq_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

Traceback (most recent call last):

File "raspberryfriend.py", line 13, in

radio.begin(0, 0,25,18) #set gpio 25 as CE pin

File "/home/pi/nrf24pihub/nrf24.py", line 381, in begin

self.write_register(NRF24.SETUP_RETR, (int('0100', 2) << NRF24.ARD) | (int('1111', 2) << NRF24.ARC))

File "/home/pi/nrf24pihub/nrf24.py", line 239, in write_register

return self.spidev.xfer2(buf)[0]

IOError: [Errno 22] Invalid argument

Here is the nrf24.py code. All I can gather is that the 'but' argument might exceed some storage limit, but the tutorial appears to have worked for others. How should I get around or fix this error? The error occurs in Python, so should I seek a solution from one of those forums?

  • are you running this as root? i.e. with sudo?
    – rob
    Jan 30, 2015 at 8:53
  • Yes, I ran the code as root. Jan 30, 2015 at 20:06

2 Answers 2


The Python spidev module has been broken (I think) since Linux kernel 3.15.x.

Its maintenance has recently been augmented with more support so I expect a new version shortly.

See Read this if you use Python Spidev.

  • 2
    I was able to update py-spidev from instructions I obtained at the link. There error is gone and everything seems to work as expected. Thank you for your help! Jan 31, 2015 at 0:08

It accepts only arrays as argument Try to place your data in an array!

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