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USART/UART PINs on STM32F429i eval board

Forum|Forum|9 months ago
May 28, 2025
5 replies
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Hello ,

Does anyone use STM32F429i eval board ?
The user manual (shown as the screenshot below) for my F429 eval board says it has 4 USART ,4 UART. But I can only find 1 DB9 male port marked as USART1.

Also, when I use CubeIDE to configure USART1, it automatically enabled PB6 and PB7 for TX and RX. But on the user manual , the schematic clearly says RS232_TX for USART1 is PA9, RS232_RX is PA10.

That's really confusing...

I am not able to find 4 USART connections, nor can I configure the right PIN numbers for USART1.

I tried to verify the Pin numbers from the github example folder, it seems they don't have the PIN number either.

This topic has been closed for replies.

Best answer by Tesla DeLorean

Yes, the STM32429I-EVAL board provides only USART1 via the RS232 or IRDA connection.

Other might be possible via the pin headers, but most everything looks to be committed to screens, external memory,etc.

I think this uses the ST-LINK/V2 and predates the V2-1 model with the VCP support. It's a rather old board design, originally from 2013

P

Pavel A.

Super User

> says it has 4 USART ,4 UART. But I can only find 1 DB9 male port marked as USART1.

This text relates to the STM32F4 chip that has so many U(S)ARTS. The EVAL *board* has only one USART1 routed to to the connector.

>I am not able to find 4 USART connections

You can find some other U(S)ARTs with "free" pins (not soldered to other functions) and make your own connectors.

The board user manual (pdf file) has reference of all pin assignments of the STM32F4 on the board.

> Also, when I use CubeIDE to configure USART1, it automatically enabled PB6 and PB7

The Cube is sometimes a bit naive, you should keep an eye on it :(

E

Embedded_AndyAuthor

Graduate II

I guess the easiest way to make it work is to buy a female RS232 DB9 to USB converter so that the STM32F4 board can communicate with PC via USART .

It is not straightforward to figure out which free pins are available to use as alternatives, maybe they are GPIO pins but I have no idea which ones and I have to use the STM32F4 chip datasheet to find 4 USARTs. Even after I found USART1,2,3,6, I cannot figure out how to use them. Pin numbers are not mentioned either...

T

Tesla DeLorean

Graduate II

https://www.st.com/resource/en/datasheet/stm32f429ni.pdf#page=75

The Table 12 shows the pin/functionality matrix, each pin has potentially 16 options

C

Chris21

Graduate

Under CAD Resources on the product web site page, you can find the schematic for the board.

There are lots of microcontroller pins that can be accessed via connectors. I think you will have to determine which ones can be used for USARTs / UARTs and are not connected to something else on the board. The USARTs / UARTs accessed via these connectors will not be RS232.

E

Embedded_AndyAuthor

Graduate II

Thank you for your reply.

I think a converter like CH340 is needed if it is not RS232.

I am considering to buy a female DB9 to USB cable converter.

K

Karl Yamashita

Graduate II

If you start a new project using Board selection and use the default settings, it selects the correct pins for USART1.

If you start a project by MCU, then it may select other pins.

If you search for USART1_RX and USART1_TX, you can see by the black pins which ones are possible for selection.

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Embedded_AndyAuthor

Graduate II

Thank you.

I do see both pins (PA9 and PB6) were highlighted when I typed USART1_TX.

I guess I can use either one of them as TX?

T

Tesla DeLorean

Graduate II

Most of the EVAL boards are crammed fully of functionality, be it RGB screens or external memory soaking up a lot of pins.

Most of the DISCO/DK board also tend to be highly committed, perhaps the only pins available for general usage being on the Arduino shield connectors.

If you need to escape a lot of uncommitted pins/functionality you should be looking at the NUCLEO boards. Or high pin-count break-out type boards on AliExpress, etc.