Help needed to understand stm32F3 discovery board schematics

[Channamallesh Hiremath]

Posted on May 11, 2018 at 07:48

On the stm32F3 discovery boards, where do pins on CN3 get connected when CN4 jumpers are on and off. 

Schematics says, CN4 jumpers on, will select discovery. Off means ST-LINK is selected. 

If I take CN4 off, then CN3 pin2 is not connected to PA14 of st32f303 device. 

I have to have CN4 on for PA14 to get connected to pin2 of CN3.

Please help me. 

[Tesla DeLorean · Accepted solution]

Posted on May 11, 2018 at 08:12

The pins in CN3 always connect to the output pins of the ST-LINK STM32F103, CN4 connects the ST-LINK to the F3 target on the board.

If you want to program an external target STM32 via CN3 then you need to disconnect the on-board target by removing the CN4 jumpers. You do this so you don't have TWO targets with SWDIO/SWCLK pins that clash and cause it so neither can be programmed/debugger properly.