RAK3272S not working

Hello

I’m trying to get a RAK3272S to work. I have hooked it up to 3.3V of a bench power supply. The UART is connected to a FTDI TTL-232R-RPi.

The module doesn’t take any current. Also double-checked with a Fluke Multimeter. Is this normal? Also, sending it AT commands via RAK SERIAL PORT TOOL doesn’t do anything.

I have also tried to pull BOOT0 to high/low. Doesn’t change anything to the current.

The same applies to the RST Pin.

Do I have a wiring issue? Or did I maybe receive a faulty module?

Ok, my fault. Got it now working.

  • The Baudrate is 9600 and not 115200.
  • The AT Command interface is just on UART2. UART1 seems to not transmit anything on the firmware v1.0.4 which is preloaded to this module.
  • Disconnecting the module from Power won’t reset it. It needs so little current that it can power itself from capacitors for multiple seconds.
  • Use picocom with --omap crcrlf flag.

Welcome to RAK forum @spinach .

It seems your module has the legacy firmware 1.0.4. If ever you will switch to RUI3, the baud rate will be now 115200. It is not really intuitive but AT CMDs and FW update is done in UART2 and not UART1. LPUART feature of STM32WL chip is on UART2 only.

All recommendations were followed but the problem still persists and I cannot find a clear answer to this problem in all forms, RAK3272s was playing but then stopped and does not respond, moreover, both devices are in the same state, TX, RX, 3.3 V, all connections are correct, the product works and data comes from the serial port but I cannot reload and it does not respond to AT commands,

How can I reset and reinstall the firmware?

Hi @CTT ,

If your module still has the legacy 1.0.4, you have to upload the RUI3 firmware using STM32CubeProgrammer. You can check the guide here how to use it.

You have to upload the hex firmware which you can get on the RAK3172 datasheet documentation - RAK3172 WisDuo LPWAN Module Datasheet | RAKwireless Documentation Center

Thank you for your answer, but I cannot access it.
Status ;
1- 3.3 V Connect To FTDI 3.3
2- GND Connect To FTDI GND
3- Boot= Connect to 3.3 V
4- UART2- TX Connect to FTDI RX,
5- UART2- RX Connect to FTDI TX,
Problems,
1- AT CMD No Ansver,
2- STM STM32CubeProgrammer no connect,

Hi @CTT ,

Some general things to check.

  1. Ensure that you are using the correct COM port number and no other application is currently using the port. In both issues you have, this can be the case since it cannot establish connection.
  2. Testing using different USB-Serial might be useful. Doing loopback test might be good as well just to remove the factor that it is the USB-Serial converter. If you validate that USB-Serial is working ok, then that would be good.
  3. Reverse the connection of RX and TX. Some marking/label on USB-Serial converter are wrong (based on some customer issue).
  4. Double check if 3.3V is stable/consistent.
  5. If you cannot send basic AT commands to the device, you will not be able to send any custom FW. You need to upload the hex file first.
  6. Ensure BOOT pin is high also you need to reset the module so it will enter the STM32WL UART built-in bootloader (not RUI3 Bootloader).
  7. If nothing works above, I am not sure if the device is still ok.