Pocket Beagle breaks python-smbus

266 views
Skip to first unread message

Graham

unread,
Oct 22, 2017, 10:00:57 AM10/22/17
to BeagleBoard
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:

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

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

unread,
Oct 22, 2017, 5:29:43 PM10/22/17
to BeagleBoard
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

==
Reply all
Reply to author
Forward
0 new messages