Error setting BAND parameter

I am using RAK3172 in an application in Greece (868 MHz)
The specific module was bought with legacy 1.0.4 firmware, and got updated to RUI 3.5.1.
While the module functioned fine, at one point communication stopped. After checking my device logs, I can see that the module refused to set BAND=4 (EU868) and defaults to BAND=1 (CN470).
I hooked it up to a UART interface to troubleshoot, and i see that the module only accepts Band 0 and 1, and returns AT_PARAM_ERROR in any other case.

I have tried reflashing the firmware, both 3.5.1 and 3.5.3 versions, but the problem remains.
What could I try to restore higher frequency functionality?

Welcome to the forum @the_lou_kou

Do you have anything connected to pin 27 (GPIO12) of the module.

As stated in our documentation this pin is used to determine whether the module for 8xx/9xx MHz or 4xx MHz.
In case you pulled it down or connected it to GND, your module thinks it is for 4xx MHz and blocks the bands for the higher frequencies.

Good to be here @beegee!

No, I don’t have anything connected on that particular pin, it is left floating on my circuit.
I measured resistance between that pin and ground, and I had ~300Ohms (different modules I have measure around ~11KOhms)

Could there be any scenario that the internal pull-up is damaged, or something else disables it? I use the module with AT commands, and since the device was deployed when this happened, I don’t see any way this could have happened from the rest of my circuit/code.

I don’t see what could damage the internal pull-up if it is not coming from external.
Could it be EMC problem, maybe a electrostatic discharge?

Can you try to pull pin 27 to 3.3V with a 10kOhm resistor and see if you can set the upper frequencies.

Unfortunately I managed to kill the module entirely while soldering and desoldering it/around it.
I hope I never need to try that again in the future, but noted in any case.

some other way to force that pin to GROUND by Software ?
because i already soldered 100 units of RAK3172 in PCB :frowning: