I2C reading of 12S battery

Nikos Mavr

Hi all,

I am trying to replace the voxl2 i2c inputs with those of an i2c power module installed closer to the supply source that can read the actual 12S source of the drone I am working on . The problem with this is that even with a level shifter or without I am not able to even find my device with i2cdetect, let alone receive readings. The module uses sen228, but i suspect that the problem could be the different pull up circuit of the different module. Could there be any feedback on that?

Eric Katzfey

@Nikos-Mavr Which pins are you using? i2cdetect is only looking at i2c ports on the Linux (applications) processor. For PX4, the standard i2c ports are mapped to the DSP (aka SLPI) so you wouldn't see them.

Nikos Mavr

@Eric-Katzfey thank you for the reply. I have tried the j4 with a level shifter and j19 ports. What would be the proper command to see them?

Eric Katzfey

@Nikos-Mavr I'm not a hardware guy so not sure on the specifics of proper level shifting, etc. But have you made sure the unit works with some other board first like an Arduino? What is the sen228 module? Is a data sheet publicly available for that? What is the i2c address? J4 / J19 i2c ports should work with PX4 running the correct driver for that module.

Nikos Mavr

@Eric-Katzfey the level shifter works properly with arduino right. The power module is holybro PM02D. Both pins are stuck to high which means communication is not successful.

Vinny

Hi @Nikos-Mavr
Please provide a drawing or sketch of your setup in question for the I2C interface, include as many details as possible so I can help you.
Thanks!
Vinny

Eric Katzfey

@Nikos-Mavr Once you get the signals figured out I added i2cdetect to px4 so you can scan the buses and see if your device is detected. Some rudimentary instructions are here: https://docs.modalai.com/voxl-px4-dev-build-guide/#i2c-debugging. You will need the latest voxl-px4 which is here: http://voxl-packages.modalai.com/dists/qrb5165/dev/binary-arm64/voxl-px4_1.14.0-2.0.135-202603171827_arm64.deb

Nikos Mavr

@Eric-Katzfey Yes, that worked, identified bus 4 channel 41. No while INA228 is enabled, I am not sure whether I should change the power_manager in voxl-px4.conf to NONE or EXTERNAL.

Nikos Mavr

@Vinny !

Vinny

Thanks @Nikos-Mavr for the drawing, that helped.
The thing to be careful about is the I2C voltage levels.
https://docs.modalai.com/voxl2-connectors/

J19 port I2C's are set to 3.3V with on-board pullups. So, I'm not sure what the 12S module I2C levels are, but be sure they are either (3.3V) or (set by host, i.e.: no pulls on the battery side)

I'm not sure what voltage is feeding into this portion... make sure it is limited to 6S:

Now that Eric has given you a bunch of guidance, let us know if there are still problems overall.

Thanks!