Programming STM32-p207 using JTAG

Question

I am a newbie learning to do ARM development. I have the following development hardware Olimex STM32-P207 & Olimex ARM-USB-TINY-H. The STM32-P207 user guide mentions the following:

Note: additionally, the board can be programmed via JTAG interface but there are signals multiplexed with the LCD and the audio, so if using JTAG interface for programming you might need to implement a software mechanism to stop them or you might not be able to reprogram again

Can anyone explain me what exactly needs to be done so that I don't mess up with my new board?

Answer 1

Some of the JTAG pins are multipurpose in STM32. During boot time, they are programmed as JTAG pins however software can override this functionality an use them as gpio. I didn't look at the board but it sounds like the pins are connected to LCD and audio.

I guess what the message saying is if you use these pins for LCD and Audio and if you do not have a mechanism not to program them, after boot, once the image from internal flash is executed, those pins will always be reprogrammed and you won't be able to put STM32 into JTAG mode. So, they ask you to implment a method (wait for x sec or if this button is pressed during boot, do not program the JTAG pins etc.)