stm32wl incompatibility with other LoRa tranceivers?

krf · ‎2025-10-20

Hi,

I have been facing with an issue that like stm32wl LoRa feature is not compability with other transceivers.

However, had 4 transceivers:

1. Esp32-sx126x

2. stm32f429-sx126x

3. stm32wl (x2)

First two can easily communicate with each others, they can exchange data even in pingpong structure but they can't send or receive data from stm32wl. In first glance, i don't know why but stm32wl couldn't be set correct syncword. After explicitly writing to its register problem solved and i could just see some thing on scanners (first two were in receiving mode) but always CRC error occurs. When third one was in tx mode and others in rx mode, others rised CRC errors and visa versa...

In other hand (without changing any configuration), stm32wls can communicate with each others.

And yes i examine and double-double check all parameters of LoRa (like sf,cr,bw,frequency).

After all question rised is there stm32wl incompatibility with other LoRa tranceivers (Specifically in CRC calculation)?

Uwe Bonnes · ‎2025-10-21

Did you check that the oscillators used provide the accuracy needed? Mismatch in frequency can result in communication failure.

krf · ‎2025-10-21

If problem is this, wouldn't be same error raise with whenever two stm32wl communicate each others?

And also have you ever tried communication with stm32wl and other transceiver? Like standalone sx1262?

Many thanks...

Andrew Neil · ‎2025-10-21

@krf wrote:
If problem is this, wouldn't be same error raise with whenever two stm32wl communicate each others?..

Not if your two STM32WLs have the same error !

That would explain how they can communicate with each other, but not with other things.

Perhaps give more details of your two STM32WL devices - are they identical designs?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

krf · ‎2025-10-21

Stm32wl devices are identical and yes their errors are CRC error. We preferred XTAL instead of TCXO. Could problem be about XTAL trimming?

Andrew Neil · ‎2025-10-21

@krf wrote:
Stm32wl devices are identical

What are they?

Please give details!

Alternatively, have you tried with known-good units - such as a Nucleo board?

@krf wrote:
We preferred XTAL instead of TCXO.

On what basis ?

How did you verify that this would give the required accuracy ?

Do your other units use TCXOs ?

Can you try with TCXOs on your STM32WL units ?

PS:

A couple of Semtech documents on oscillator selection/design:

AN1200.59 Selecting the Optimal Reference Clock.

AN1200.14 LoRa Modulation Crystal Oscillator Guidance.

See also the Documents section on the SX1262 Product Page.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

krf · ‎2025-10-21

What are they?

- They are custom designed LoRa boards that includes stm32wle5. It is custom but mainly reference design from st is took as reference. Also it should operate in 915 MHz but due to wide band of transceiver, i tried many frequency but results were same. Also we chose +15dbm Rfo_LP configuration and power supply selection made according low power selection!

For reference design please refer attached file!

Alternatively, have you tried with known-good units - such as a Nucleo board?

- I tried P-NUCLEO-LRWAN2 gateway board but it didn't receive any thing from customized stm32wle5 boards but it can receive data from other units. (nucleo Gateway link)

On what basis ?

-Price was a point and also semtech says you can choose XTAL over TCXo. Also we haven't an expectation that temperature might change too much in working environment.

How did you verify that this would give the required accuracy ?

-I asked it hardware designer which XTAL he choosed. After getting information, i will inform you.

Do your other units use TCXOs ?

- Yes, you can check DRF1262T (transceiver datasheet)

Can you try with TCXOs on your STM32WL units ?

-Unfortunately no. It would take so much time designing, manufacturing etc...

Andrew Neil · ‎2025-10-21

@krf wrote:
Alternatively, have you tried with known-good units - such as a Nucleo board?
- I tried P-NUCLEO-LRWAN2 gateway board

That doesn't use an STM32WL, though - does it?

I mean, have you tried using a known-good STM32WL device?

Does a known-good STM32WL device communicate with your Esp32+sx126x and stm32f429+sx126x devices?

known-good STM32WL device communicate with your custom WL-based devices?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

krf · ‎2025-10-21

Ah, Unfortunately no. I hadn't chance to try it. Those nucleo boards hasn't stm32wle. Instead it uses stm32 mcu and seperate LoRa transceiver.

So, do you have any experience that stm32wle can communicate other LoRa transceiver because examples that i examined only shows two stm32wle are communicating each others.

bmckenney · ‎2025-10-21

Check the value of XTAL_DEFAULT_CAP_VALUE; the default value is very large -- enough to throw the ~~HSE48~~ HSE32 off-frequency. (As Andrew mentions, if both sides are affected the same way, they'll still be able to communicate.)