I2C behaving strangely on ALL-H3-CC-H5

[Breadycorn]

Hello,

I have been trying to get my Tritium to communicate with my Arduino UNO R3 using I2C.

I know of the voltage difference (tritium 3.3v vs Arduino 5v) and got a bunch of bidirectional logic converters.

I hooked it all up:

Tritium 5v - Arduino VIN
Tritium GND - Arduino GND

Tritium 3.3v - Logic converter LVin
Tritium GND - Logic converter LVGND

Tritium pin 3 - Logic converter LV1
Arduino SDA pin - Logic converter HV 1

Tritium pin 5 - logic converter LV2
Arduino SCL pin - Logic converter HV2

Arduino 5V - Logic converter HVin
Arduino GND - Logic converter HVGND

I configured my Arduino following a tutorial on YouTube to receive on I2C address 0x8 to turn the led on and off, just as a way to test it.

Now running

sudo i2cdetect -y 0

gives me random I2C adresses but no address 0x8. Also running the command multiple times gives me a different output every time.

I also tried disconnecting all the cables from my Tritium and I still get random I2C adresses. You can see the output on my screenshot. (Screenshot is without any I2C devices connected. So it should give an empty list, but the list changes every time)

I’m running Ubuntu Desktop with multi-user.target

[angus]

Hi!

Have you applied a Device Tree Overlay? Usually the I2C bus created when an overlay is enabled comes after the bus used by the board. I believe what you’re seeing is a built in EEPROM or some-such on an I2C bus that is used for the boards own purposes.

Here’s the how-to:

Libre Computer Wiring Tool

To install via apt: sudo apt update sudo apt install libretech-gpio libretech-dtoverlay libretech-gpio To get a list of headers for your board: lgpio headers To get a list of the header pins for a header: lgpio header HEADER For getting the information for a pin number on the main GPIO header of the board: lgpio info PIN# For getting the information for a pin number on a specific header of the board: lgpio info HEADER PIN# For getting the libgpiod chip and line number for a pin on th…

This is what it looks like on the AML-S905X-CC (I don’t have one of the Allwinner boards to test with. My I2C device lives at 0x36.):

angus@aml-s905x-cc:~$ sudo i2cdetect -y 0
[sudo] password for angus: 
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: 30 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         
angus@aml-s905x-cc:~$ sudo i2cdetect -y 1
Error: Could not open file `/dev/i2c-1' or `/dev/i2c/1': No such file or directory
angus@aml-s905x-cc:~$ sudo ldto enable i2c-ao
Overlay i2c-ao: applied
angus@aml-s905x-cc:~$ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- 36 -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         
angus@aml-s905x-cc:~$ 

[Breadycorn]

I don’t really understand, do you think I need to install the device tree overlay and it will somehow allow me to use the I2C pins? I’m really new to all this GPIO, SBC and Linux stuff, I’m still trying to get my bearings

[angus]

Yes, again, I’m using a different board, so my pins/overlays will be different, but you need to enable the I2C bus you want to use in the device tree, or the kernel doesn’t know it’s there.

The wiring tool should come pre-installed if you’re using one of Libre’s images, and the command ldto list will tell you what overlays are available for your board.

It’s a bit different than what I get on my board, but it looks like sudo ldto enable i2c1-twi0 should get you up and running on pins 3 and 5, using /dev/i2c-1. If I’m wrong hopefully someone with and Allwinner board in hand can correct me.

You will need to reapply the overlay after each boot. You can add it permanently by replacing “enable” wit “merge”. Be aware on my board this flips the busses, so the internal use bus becomes i2c-1 and the one I attached my device to becomes i2c-0.

Hope that sheds some light. The Device Tree is a huge topic, so don’t worry if you don’t get it all at once!

EDITS: Corrected spelling, and it’s open on my browser so I may as well link to the pin-maps:

GPIO Pinout Header Maps and Wiring Tool for Libre Computer Boards

Below are links to spreadsheets with the GPIO and its pinmuxes. These are derived from the board schematics. ALL-H3-CC AML-S805X-AC AML-S905X-CC AML-S905X-CC-V2 identical to AML-S905X-CC AML-S905D-PC AML-S905D3-CC AML-A311D-CC ROC-RK3328-CC ROC-RK3328-CC-V2 identical to ROC-RK3328-CC ROC-RK3399-PC ROC-RK3399-PC-V1.2 Also see Libre Computer Wiring Tool and Libre Computer Pinmux Compatibility Matrix.

Also corrected overlay as noted below.

[Breadycorn]

I tried with enable first, it worked! I got a completely empty list without anything attached and plugging in the logic converter I got something on 0x8!

The one I had to activate was i2c0-twi0 (according to the pinout thats on pin 3-5, i2c1-twi1 is on pin 20something)

I broke a cable off my logic converter while trying to get it into my enclosure, so testing the Arduino sketch will have to wait, but so far I feel like I’m a major step closer, being able to see the Arduino on address 0x8 means that at least this part of my sketch works!

Thanks a lot for your help, I found that first article you linked before but didn’t make the connection with I2C since it’s not mentioned anywhere.

[angus]

Sorry about the pin confusion, it was my first time looking at the docs for that board. Glad you got it working! Happy tinkering!