MC33772C - Data loss issue with 16 AFEs on TPL bus

[louispelletier]

Hello,

I've had a BMS working great with small number of AFEs (1-6) per bus but we are trying out a bigger pack this time and I'm getting some random data loss when I have 16 AFEs on the bus.

I'm trying to keep the refresh rate on each of them below 1s (every 500ms at the moment) but once in a while some of them just seem to timeout. They also sometime come back online and I can read the data again.

I'm suspecting a hardware issue but I'm wondering if there is something software I could do to prevent this.

***EDIT***
I was able to pinpoint the following error when communicating on the bus: 

BCC_STATUS_COM_MSG_CNT or BCC_STATUS_COM_ECHO or BCC_STATUS_COM_CRC

They seem to be random and not necessarily on the same BCC.

What would be the way to correct this?

Thank you!

[JozefKozon]

Hello Louis,

yes, this is most probably the hardware issue. Please refer to the AN12626. With more nodes in the daisy chain, an attenuation and overshoot of the TPL signal comes into account and you need to take measures to avoid it to acceptable level so the TPL signal will be recognizable. Please also refer to the AN12710, to AN13281 and to AN12963. The last two are however confidential and you need to have a valid NDA with NXP to be able to download them. You can download them from the MC33771C product page, under the secure files. 

With Best Regards,

Jozef

[louispelletier]

Hello Jozef,

Thank you for the feedback, we will definitely check back our hardware designs. The only missing application note we didn't have was AN13281.

Would these problems be more frequent under load? I don't seem to have the communication losses when the pack is idle on a tabletop. It happens only under load at the moment.

Finally, would there be any software mitigation strategy we could use in the meantime we update our hardware?

Thanks again,

Louis

[JozefKozon]

Hello Louis,

for the software you can refer to MC3377xC software package in this link. If you are using our S32K144 MCU, there are some examples for this. You can check the software configuration for the daisy chain.

With Best Regards,

Jozef