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graycatlabs / PyBBIO

A Python library for Arduino-style hardware IO support on the Beaglebone
https://github.com/graycatlabs/PyBBIO/wiki
MIT License
251 stars 89 forks source link

SPI0.write crashes Beagleblone #106

Open jonturner53 opened 7 years ago

jonturner53 commented 7 years ago

Running the following code causes the BeagleBone to crash when it gets to the SPI0.write() call. To recover, I have to reset the board. Am I doing something wrong here?

I am new to both the BeagleBone and PyBBIO, so I may be making a newbie error. However, I have run a few tests involving the GPIOs and they all seem to work ok. The blinking led example works fine, so I think the installation is ok. I currently have no circuits connected to the board, so the tests using the GPIOs are just wiggling pins (I have checked a few using a multi-meter, to make sure they're responding).

Jon Turner

import sys
from bbio import *

def setup():
    SPI0.open()
    SPI0.setClockMode(0,0)  
    SPI0.setMaxFrequency(0,1000000) 
    SPI0.setBitsPerWord(0,10) 
    SPI0.setMSBFirst(0)

def loop() :
    print "about to write"
    SPI0.write(0,[0x15])
    print "done"
    sys.exit(0)

run(setup, loop)
alexanderhiam commented 7 years ago

See this issue on the serbus library (which PyBBIO uses): https://github.com/graycatlabs/serbus/issues/1

It looks to be an bug in the omap2-mcspi kernel driver, so unfortunately nothing can really be done about it at the PyBBIO level. You could try using 12 or 16 bit words - in my experience SPI slave devices that use weird word sizes often just work with larger words.