Need help with i2c and displayotron hat


#1

I’ve got a problem where I can’t seem to get the displayotron hat to do anything because I keep getting the error “IOError: [Errno 121] Remote I/O error”. I believe this is a problem with my i2c set up, but I can’t seem to find a resolution. (I tried reducing the speed which did not help.) Here is the output I get, for example:

jbf@gardenhousepi:~/displayotron/displayotron/examples/dothat/basic $ python
Python 2.7.13 (default, Nov 24 2017, 17:33:09)
[GCC 6.3.0 20170516] on linux2
Type “help”, “copyright”, “credits” or “license” for more information.

import dothat.backlight as backlight
Traceback (most recent call last):
File “”, line 1, in
File “/usr/local/lib/python2.7/dist-packages/dothat/backlight.py”, line 1, in
import sn3218, colorsys, math
File “/usr/lib/python2.7/dist-packages/sn3218.py”, line 114, in
enable_leds(0b111111111111111111)
File “/usr/lib/python2.7/dist-packages/sn3218.py”, line 62, in enable_leds
[enable_mask & 0x3F, (enable_mask >> 6) & 0x3F, (enable_mask >> 12) & 0X3F])
IOError: [Errno 121] Remote I/O error

Has anyone dealt with this? Is there an easy way to verify that i2c is not working?
Jeremy


#2

Is the HAT mounted securely, directly on top of the Pi?


#3

Joy, thank you! New users of this device should be aware that it is easy (with a dark case) to seat the display-o-tron incorrectly, with the pins misaligned. The top corner of the display-o-tron hat should line up with the corner of the pi, and a voltmeter can be used to verify a 5 volt potential can be read across the “5V” and “GND” pins.


#4

Eek! Believe me when I say that I’ve seen HATs and other Pi addons seated incorrectly in every conceivable way and have done it myself plenty of times (even recently). Glad you’re up and running!