STM32G431 Flash from UART Problem

[BG1]

Hello , I'm using Nucleo-G431RB board , and I am trying to flash the MCU via UART1 using PA9 and PA10 pins but I can't make it work ..

I get an error like "Error: Activating device: KO. Please, verify the boot mode configuration and check the serial port configuration. Reset your device then try again... "

I'm using STM32Cube Programmer , also I followed the instructions in AN2606 , the application note states that it should follow pattern 15 , as far as I can view the option bytes using the onboard ST-Link , nSWBOOT0 comes unchecked so software decides if it should run starting from bootloader address .. My settings for UART are 9600 Baudrate , Even parity . NBOOT0 and NBOOT1 comes checked so it seems it is not applicable for any pattern to jump bootloader mode , So I tried setting NSWBOOT0 so it matches the pattern stated "BOOT_LOCK(bit)=0, Boot0(pin) = 1, nBoot1(bit) = 1 and nBoot0_SW(bit) = 1" , I manually tied BOOT0 to 3.3V and when I reset the MCU I can verify that it starts at bootloader mode , what makes me think like that is the observation on behaviour of some pins using scope , It is not the code running the user flash .. Also I can say that my UART com bridge is sending 0x7F but there is no response coming out of the MCU at all .. Where do I do the mistake .. any help would be appreciated .

[Javier1]

did you checked the wiring is TX-RX RX-TX?

Which USB-UART bridge are you using?

Pa9 and PA10 are not connected to anything else in the nucleo board so it should be ok

[BG1]

It is one of those CP2102 using bridges , and yes I double and tripple checked . Besides I can communicate with the MCU with my user code ..

[Javier1]

your UART config should be okay also, did you set 8 bit and 1 stop bit?

[Javier1]

 

Maybe is worth to hook up an oscilloscope to take a look to your signal integrity

[BG1]

I watch the voltages and they are pretty clear ..

[BG1]

A question out of curiosity , as for the document RM0440 , it claims for the option byte ST production value to be 0xFFEF F8AA .. But for the NucleoG431RB board Option Byte value was read as 0xFBEF F8AA as default (nSWBOOT0 = 0 by default) ? So , how does one run it from the bootloader mode and flash it over UART1 very first time ...?