STM32G491 bootloader doesn't work

[ERazz.3]

hi, i'm using a STM32G491 and i can't use embedded bootloader over UART1. 

i'v set BOOT_LOCK(bit) to 0, Boot0(pin) to 1, nBoot1(bit) to 1 ans nBoot_SW(bit) to 1. 

when i try to connect the mcu to STCubeProgrammer over UART i receive this message error:

 17:18:05:955 : Serial Port COM7 is successfully opened.

 17:18:05:955 : Port configuration: parity = even, baudrate = 115200, data-bit = 8,           stop-bit = 1.0, flow-control = off

 17:18:05:955 : No Init bits value is : 0 

 17:18:05:955 : Sending init command: 

 17:18:05:957 : byte 0x7F sent successfully to target

 17:18:07:956 : Wait ends after 1 loop, dataready = 0, delay = 2001

 17:18:07:956 : Timeout error occured while waiting for acknowledgement.

 17:18:07:956 : No response from target received

 17:18:07:957 : byte 0x7F sent successfully to target

 17:18:08:056 : Wait ends after 1 loop, dataready = 0, delay = 100

 17:18:08:056 : Timeout error occured while waiting for acknowledgement.

 17:18:08:056 : No response from target received

 17:18:08:056 : Error: Activating device: KO. Please, verify the boot mode configuration and check the serial port configuration. Reset your device then try again... 

 17:18:08:128 : UART PORT CLOSE 

someone can help me?

[Tesla DeLorean]

>>someone can help me?

Is this a custom board?

What type of serial connection?

To what pins?

Is board otherwise functional? Can you connect via JTAG/SWD?

UART expects 3V CMOS levels, not RS232

Have you scoped the pins, can you send the 0x7F data pattern via other tools/terminal? Any response there?

Any other pins listed in AN2606 with active signals? ie GPS/GNSS receiver connected to secondary UART?

State of NRST pin?

[ERazz.3]

yes, it's a custom board.

"What type of serial connection?", pardon, what do you mean?

the serial is connected to pin PA9, PA10.

yes the shield works and I can connect to it via jtag.

i've tried to send pattern via minicom (on raspberry pi CM4) and docklite (windows 10 pc).

also in this case I have not received any response.

the state of NRST pin il high when i try to send 0x7F

[ERazz.3]

I correct myself.

only now, after many attempts. i got something on serial. (using docklight)