I'm trying to setup the alphanumeric i2c backpack https://www.adafruit.com/products/2158 with a BeagleBone Black, and I'm having trouble connecting via I2C. I have wired up the backpack, and have followed the tip here http://beaglebone.cameon.net/home/i2c-devices to activate I2C1. Although all three I2C buses appear in i2cdetect -l ...
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$ sudo i2cdetect -l
i2c-0 i2c OMAP I2C adapter I2C adapter
i2c-1 i2c OMAP I2C adapter I2C adapter
i2c-2 i2c OMAP I2C adapter I2C adapter
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$ sudo i2cdetect -r 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
My problem sounds somewhat similar to the error here http://forums.adafruit.com/viewtopic.ph ... ck#p295675, but I cannot find a wiring error (see picture below). I have reproduced this issue with two identical BeagleBones and I2C backpacks, so it's clearly something I've done wrong and it's not a manufacturing error.
http://pasteboard.co/2qgumFKT.jpg
Edit #1: Just as I was about to give up, the board briefly appeared on I2C2.
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$ sudo i2cdetect -r 2
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: 70 -- -- -- -- -- -- --
Edit #2: I was able to get it to show up reliably by connecting VCC to 3.3V (rather than 5v). Now the problem seems to be something buried deep in the Adafruit library. See error below.
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$ sudo python alphanum4_test.py
Traceback (most recent call last):
File "alphanum4_test.py", line 33, in <module>
display.begin()
File "build/bdist.linux-armv7l/egg/Adafruit_LED_Backpack/HT16K33.py", line 52, in begin
File "build/bdist.linux-armv7l/egg/Adafruit_GPIO/I2C.py", line 122, in writeList
IOError: [Errno 121] Remote I/O error