Is it necessary to disable VCP to acces USART1 via pins PA9 and PA10 on STM32F429I-DISC1 (E01) ?

[AMORI.1]

Hello,

I am trying to connect to my STM32F429I-DISC1 (E01 revision) board's USART1 on pins PA9 and PA10 using an FT2232HL as USART to USB interface.

I've seen in the user manual of the STM32F429I-DISC1 that the solder bridges SB11 and SB15 connecting ST-LINK to USART1 and enabling VCP where on by default.

I am wondering if this might prevent me from accessing USART1 via pins PA9 and PA10 and if I have to disable this solder bridges or if it has no incidence over it ?

​Thank you.

[Andrew Neil · Accepted solution]

You can have two receivers driven by one transmitter:

          +---->Rx1 in
          |
Tx Out--->+                          This is OK
          |
          +---->Rx2 in

but you cannot short two transmitters together to drive one receiver:

Tx1 out---->+
            |
            +---->Rx in                          This is NOT OK
            |
Tx2 out---->+

[AMORI.1]

Alright thank you. If I understand correctly this means that I have to disable the SB connecting Tx to st-link.

[Andrew Neil]

No.

The STM32 Tx output can go to both the ST-Link and the FTDI's Rx inputs.

It's the ST-Link's Tx output that you need to disconnect.

[Andrew Neil]

                +---->ST-Link Rx in
                |
STM32 Tx Out--->+
                |
                +---->FTDI    Rx in
 
 
 
ST-Link Tx out---->  disconnect!
 
                   +---->STM32 Rx in
                   |
FTDI    Tx out---->+

[AMORI.1]

Oops my mistake, I was thinking from the point of view of the st-link controller and replied too fast.

[Andrew Neil]

Nobody has ever got Tx and Rx the wrong way around before ...

:face_with_tears_of_joy: :grinning_face_with_sweat: :confounded_face:

If that's resolved the issue, please mark the solution