RAK3172 not responding after power failure

Morning, I have recently completed some stress testing on our battery powered device which uses the RAK3172. The device was run in a worst case scenario such that the battery was flat after a month of testing. When the device was repowered with a fresh battery the device started working again however the RAK3172 was no longer responding to any communication over the UART.

We have seen this behaviour on at least one other device.

Hello Marina,

What RUI3 version do you have on the RAK3172?

How is the battery connected to the device? Is it a connector or are the battery wires soldered directly to the device?

What kind of battery are you using?

The battery is connected to the device via a connector and the battery in use is a Lithium Thionyl Chloride 3.6V AA battery. The battery voltage is fed through a regulator providing a 2.5V supply to the RAK3172.

In terms of firmware versions on the RAK module it is either 1.0.3, 4.0.0 or 4.0.2. Unfortunately as the module is no longer responsive I am unable to determine the exact firmware version.

1 Like

Good afternoon.

I have the same problem, after carrying out tests by turning the module on and off it stops responding.

I use a 5VDC input and an LDO for 3V3 for the RAK.

Welcome to the forum @leocsbh007

What firmware version?

V1.0.4 or older?
RUI3 ?
Custom firmware with STM32CubeIDE?

Hi, thanks @beegee!

I’m using version 3.4.2 RUI3.

I recommend to upgrade to RUI3 V4.0.6, the latest released version.

Are you using the AT command interface with a host MCU or a custom firmware based on RUI3 API?

Yes, I am using the AT command.

I saw a note in the manual, one of my parts was without an antenna and in transmitter mode, will the module be damaged?

It is never good to use the device without antenna, but I think more your problem is related to another problem we fixed in the latest RUI3 versions.
The problem was related to fluctuating supply voltage and triggered an NMI that stopped the device from booting up (even after power cycle).
I would try to flash the latest firmware over the SWD interface and check if the RAK3172 boots up again.

OK. Where can I find the new version of RUI?

Is there any detail to use SWD with STM Programmer?

STM32Cube-Programmer-Guide ==> Using ST-link debugger programmer tool

RUI3 Download Center

I updated the FW version as you indicated, using SWD (RUI_4.0.3_RAK3172-E.bin), but the module continues to not respond to AT commands.

I imagined that the module’s PA2 and PA3 pins were burned, so I wrote a FW version via Cube IDE, to send and receive data via the serial and it responded.

Attached pictures!!!