Nxp rddrone-bms772 communication problems

ArduCopter Copter 4.4
1

This may not be an Arducopter bug, but I’m not sure. I have a NXP RDDRONE-BMS772.
The communication can be set to SMBus in the BMS. After a few minutes the communication breaks. I had Copter 4.3.8 at first and had seen this change in the release notes of 4.4: DMA for I2C disabled on F7 and H7 boards
so today I updated to 4.4. But the effect is still there. By the way, when the communication breaks down in flight, no battery failsafe is triggered, is this intentional?

Hardware is Cube Orange Plus
BMS on I2C 1 on address 8

2

So you had at some point this board https://www.mouser.de/ProductDetail/NXP-Semiconductors/RDDRONE-BMS772?qs=vHuUswq2%252BswZTzyulwZ84g%3D%3D&gclid=EAIaIQobChMI2ZLU9K6sgQMV31WRBR3N3QKvEAAYAiAAEgKBgfD_BwE working with ArduCopter? Nice!

Try the 4.5.0-dev version. there has been some changes regarding DMA that got merged a couple of days ago.

3

Yes, it seems that way, except for this problem. I just had to find out that the BMS is configured on address 8 instead of 11, which was poorly documented.
Todos would be to implement dronecan instead of uavcan, then it would be perfect.

Thanks for the tip, I will test it and report back here.

4

Here’s what we’ve tested now:
With a Cube Black Copter 4.4, communication remains stable indefinitely.
With a Cube Orange+ Copter 4.5 dev, the communication interrupts after some time, as already with 4.4.
Now we have inserted PullUp resistors in the I2C line at the Cube and it seems to work like this

5

What resistor values have you used?
Pulling up to 3.3V or pulling up to 5V?

6

pulling up 5V with 3.3k ohm