Cant power B-L072Z-LRWAN1 with battery

[KPage]

We recently received our B-L072Z-LRWAN1 but are not able to run the program while batteries are plugged in. In the datasheet it says that we need to remove SB37 to accomplish this. But then I cant program it anymore? How can I use the board with battery only and still be able to program it?

[Andrew Neil]

So it is definitely not the same problem!

[REste.1]

I have the same problem. Opening the SB37 the board continue not transmitting.

[PMART.11]

Good morning.

I would like to know if someone has solved the problem because I have the same problem and I have already tried a lot of things. The program cannot be operated with any other power source than the USB. However, the LED07 is powered on with all 3 batteries.

Thanks a lot !

[Andrew Neil]

@PMART.1​ "I would like to know if someone has solved the problem"

What problem, exactly?

Multiple posts above have said that removing SB37 (as the User Guide instructs) fixed their "problems".

@aperles​ had a completely different problem - and posted the workaround to that problem.

[Andrew Neil]

@aperles​ "I'm using the workaround proposed in https://ask.sigfox.com/questions/7717/cmwx1zzabz-blocks-on-tx-start-unless-pa2-and-pa3-a.html and things started working. It is related to the LPUART"

That link now seems to be broken.

But the solution is repeated here:

https://community.st.com/s/question/0D50X0000BVnwauSQB/cmwx1zzabz-with-stm32cubeexpansionsfoxv110-blocks-on-txstart-unless-pa2-and-pa3-are-physically-pulled-up-and-configured-as-lpuart

[aperles]

Hi,

@PMART.1​  As Andrew comments, I've solved this problem by changing the configuration of the LPUART. If you use the workaround of connecting directly the PA2 and PA3 to +Vcc is too aggressive and you could burn out the micro.

That being said, consider that the Murata cmwx1zzabz module is suffering from a shortage, so developing based on this is not a good idea right now.

If you seek dual Sigfox-LoRaWAN operation, then I suggest considering something based on the STM32WL series.

Best,

�?ngel

[Andrew Neil]

Having made mods to run on battery / get minimum power, here's a post on how to reconnect the ST-Link for programming & debug:

https://community.st.com/s/question/0D53W00001XvfJtSAJ/restore-stlink-connection-on-bl072zlrwan1