Permanently damaged Radio RX path on STM32WB55

Aku · ‎2021-02-05

Hi,

we've been developing with stm32wb55 for some time and found that some combinations of STOP2 and radio usage causes permanent damage to RX path.

It looks like that: device announce stops at some point and power consumption raises(+10mA). After reset device starts announce again, but doesn't receive anything.

Flashing TransparentVCP and checking RX with CubeMonitorRF shows RSSI -108dBm

Wiping flash and re-flashing radio and firmware doesn't help.

Overall we've been following all application notes on power, radio, LSE/HSE. The only significant difference is antenna(we use IMD by Ethertronics/AVX 1001312) and software(we use STOP2 in between announces and prevent sleep only when connection arrives).

Disabling STOP2 prevents damage, but completely unacceptable in terms of UX and power consumption.

Since radio is a black box we are completely puzzled by this behavior and were unable to trace cause of damage.

Is there any way to examine radio path internals (like on st25)? As I understand AT0, AT1 exists exactly for that purpose.

Or any other ways to find what may cause RX path damage?

Aku · ‎2021-02-11

@Remi QUINTIN any news?

Remi QUINTIN · ‎2021-02-11

Yes. Your issue is now investigated by the American region.

Case 00125384 is being handled by the RF team in US.

They should be your first level contact now.

Msafa.1 · ‎2021-02-26

Hi @Remi QUINTIN , @Aku @Pavel Zhovner

We seem to have the exact same problem here, the RX path is permanently damaged. can we also be included in the discussions? we are also just about to introduce a product to market at large volumes...

Aku · ‎2021-02-27

Hi,

sad to hear that. You can open new support case and refer to 00125384, so they can join our issues together.

Here is what we know:

Looks like some kind of condition race in core2 firmware
Happens when IP_CORE_LP_STATUS and PES_ACTIVITY led is on (try to enable it in app_debug.c and confirm that you have it)
Power consumption increase and depends on SMPS status (+5mA if enabled, +10mA if not)
It takes time to do the real damage after core2 arrives to this state
Arriving to this state correlates with stop mode usage, but not limited to it.
With some probability damage happens only in stop mode.

ST Support recommendations:

Check HSE: WB/WL series have embedded load capacitors for calibration, make sure that you follow https://www.st.com/resource/en/application_note/dm00403796-precise-hse-frequency-trimming-using-stm32-wireless-mcus-stmicroelectronics.pdf
Check LSE: make sure that it's working correctly
Make sure that there is no current injection in antenna path, replace inductor with capacitor between MCU and filter and check if issue is reproducing
Try to reproduce issue with examples (that's where we are now)

Also we can make discord/slack/email channel to discuss this issue, drop me a private message if you'd like to participate

Msafa.1 · ‎2021-02-27

Thanks @Aku , just sent you a private message.