USART1 TX on PA9

[rdurand9]

Posted on November 12, 2011 at 19:15

Hi,

I would like to use the USART1 TX on pin PA9 but evan I remap usinf AF (alternate function), the USART1 doesn't transmit on PA9, it is like the USB OTG FS is keeping the pin. I would appreciate it a lot if somebody could tell how I can use PA9 to transmit USART1. Best Regards, Richard

[Tesla DeLorean]

Posted on November 12, 2011 at 22:50

Present the code, or look at the earlier USART3 code thread.

Look at the example USART code in the F2xx standard library code, the differences to the F4xx should be pretty minimal.

[rdurand9]

Posted on November 13, 2011 at 02:02

My code is fine because when I rempa de USART1_TX on pin PB6 everything is working fine but when I remap it on pin PA9 the TX is not working because OTG_FS_VBUS is keeping the pin.

According tor the datasheet STM32F407xx it is written that the function is remapped through peripheral registers but I don't know how to shut down that remapping.

[danielczigany9]

Posted on November 14, 2011 at 09:17

Hello,

If you see in the STMF4 Discovery user manual then you can see(page 34): on the PA9 there is a 4.7uF capacitor. If you want to use UART1 TX then you must remove this component and you must care about PC0, you must keep it HIGH. I suggest use UART6, the pins for UART6 is near to UART1 on the header. (PC6 Tx, PC7 Rx).

[rdurand9]

Posted on November 15, 2011 at 01:46

Hi,

You were right, after having removed the 4.7uF capacitor the USART1_TX on pin PA9 worked. Great !! Thanks a lot rd