Posted on May 17, 2011 at 13:32I had the same problem as alex4 (above) and would like to add my feedback so others will not have to struggle with this problem (as I also did).
I followed the application note (AN2662 - Doc ID 14156 Rev 2) as well as the errata sheet (STM32F105xx and STM32F107xx Errata sheet - Doc ID 15866 Rev 2) to a ''T'' and could not get the bootloader to recognize the MCU to download firmware into the chip using USART1. The latest ''Flash Loader Demonstrator'' tool (version 2.1.0) would give the error message ''Unrecognized device'' when trying to connect to the MCU. Using my scope I could see that the tool was indeed sending the ''0x7F'' code to the MCU on the PA10 line (USART1_RX) and I could see that the PA9 line (USART1_TX) would send back the ''0x79'' acknowledge byte, but not at the same baud rate, so obviously the tool could not recognize the device.
I'm using the STM32F105VBT6 device (date code 926) on my new PCB design with all the pins terminated as per the device data sheet and application notes. I pulled up PD6 and PB5 each with a 10K resistor to +3.3 VDD (as per AN2662 for USART1). The clue to fix this problem came from alex4's response where he pulled up ALL 4 lines (not 2) to get the bootloader to work. I then pulled up PA11 just to see if it would make any difference and it did - it started to work after that (PA12 was still pulled down). So it appears that even the errata sheet is incorrect. The line pertaining to USART1 on Page 20 of the errata sheet should be changed from:
''If USART1 is used to connect to the boot loader: PD6 and PB5 have to be kept at a high level''
to:
''If USART1 is used to connect to the boot loader: PD6, PB5 and PA11 have to be kept at a high level''
I'm not sure if any other combination of pulled up pins would work, but this combination worked for me.
