After updating bootloader to v3.3.0.18 DFU no longer updates

After i briked with DFU i dicided to reflash fresh. So i downloaded the latest firmware and with the help of stlink_v3 i flashed firmware with file RAK4270_v3.3.0.18_Boot+App_20211217.hex.

After that DFU 1.4 just give me timeout…

But with serial port tool i can talk with AT comands no problem.

Is the latest version of bootloader broken?

Hi @xistoso ,

When you upload the hex file did you use STM32CubeProgrammer? Did you set anything on it when you use the stlink_v3 or just the default setting?

I tried it with my RAK4270 with FW and DFU is working ok. Also, you can check if the baudrate on the DFU is 115200 and if the port is correct.

I re-uploaded the same FW and it continue with out timeout.

Ty for the prompt response @carlrowan ,
yes, i just flashed it with STM32CubeProgrammer default settings.

I can ATT command in FW.
But still i’m buying a new serial tool and get it out of the equasion. Mine is an Original FTDI chip. But quite old. Also need another.

I met with a similar problem. After flashing FW (by STM32CubeProgrammer+STLink v2 flashing HEX), the module does not respond to anything. After flashing to FW, the module connects to the DFU. However, when an application getting from the RUI online compiler is download to the module via DFU, the module firmware version is upgraded to and continues to work correctly with DFU.