Pocket Beagle breaks python-smbus

[Graham]

I am trying to run some Python control of I2C devices on the Pocket Beagle (PB)

that already run on the BBB (Rev C).

So, I set up the following comparison:

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Load fresh "bone-debian-9.2-iot-armhf-2017-10-10-4gb.img" on the BBB Rev.C

Linux beaglebone 4.4.91-ti-r133 #1 SMP Tue Oct 10 05:18:08 UTC 2017 armv7l GNU/Linux

sudo apt update

sudo apt install python-smbus python3-smbus

i2cdetect -y -r 2       # reveals target part at bus 2, addr = 0x18

python2

>>> import smbus

>>> b = smbus.SMBus(2)

>>> print b.read_word_data(0x18,0x06)

21504

# expected result (Manufacturer ID for MPC9808 temp sensor)

python3

>>> import smbus

>>> b = smbus.SMBus(2)

>>> print (b.read_word_data(0x18,0x06))

21504

# expected result (Manufacturer ID for MPC9808 temp sensor)

----------------------------------------------------------------

Load fresh "bone-debian-9.2-iot-armhf-2017-10-15-4gb.img" on the PB.

Linux beaglebone 4.4.91-ti-r133 #1 SMP Tue Oct 10 05:18:08 UTC 2017 armv7l GNU/Linux

i2cdetect -y -r 2       # reveals target part at bus 2, addr = 0x18

sudo apt update

sudo apt install python-smbus python3-smbus

python

>>> import smbus

>>> b = smbus.SMBus(2)

>>> print(b.read_word_data(0x18,0x06))

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

IOError: [Errno 121] Remote I/O error

python3

>>> import smbus

>>> b = smbus.SMBus(2)

>>> print(b.read_word_data(0x18,0x06))

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

OSError: [Errno 121] Remote I/O error

The only thing unique about this PB is that I am using a USB-2 to Ethernet interface for SSH access on USB1 port. Driver is already included in the kernel/img.

Should not have any impact on I2C operation. I2C is not used by the Ethernet, just USB.

----------------------------------------------------------------

[Graham]

Please disregard...

I had a strange hardware grounding problem that allowed "i2cdetect" to see the part, but could not communicate with the part.

I2C working as expected on the PocketBeagle, now.

--- Graham

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