my ESP8266-12 was welded on my stm32 board ,connecting by usart2.
and i want to update the firmware of ESP8266,so I program STM32 to transmit DownloadTool data for me,at the same time forward 8266 data to DownloadTool ,like this:

i finished the program and log from ESP Flash download tool V3.4.9.2:


download setting:

the tool can read the info of 8266 through stm32,and erase the flash,but can't download the program.
so is there any chance that the data transmited wrongly when passing through the STM32?is there any way to check?
thanks!