Communication between Nucleo-F411RE and Raspberry Pi using ST-Link VCP

[suhfi]

Hello, i am using STM32F411RE with raspberry pi 4. i want to communicate rasp with stm32 through usb cable from pi to CN1 of stm32. i want the communication both ways. could you please tell me how to do it?
Thank you in advance.

[SofLit]

Sorry I didn’t understand the content of the image you shared!

[Andrew Neil]

OK, I just dug out an RPi and Nucleo board, and tried it.

Before plugging-in the Nucleo board:

After plugging-in the Nucleo board, I get the pop-up for the MSC:

and there is a new /dev/ttyACM0:

@suhfi so here,  the /dev/ttyACM0 is the ST-Link's Virtual COM Port on the Raspberry Pi;  you use it just as you would use any other "COM port" (ie, /dev/tty... device) on a Linux system - there is nothing special or specific to STM32 as far as Linux & the Raspberri Pi are concerned.

The actual /dev/tty... device assigned may be different - just like you get different COMxx: numbers in Windows - so use the above method to discover what device is created on your particular system.

[Andrew Neil]

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@suhfi wrote:

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That's on Windows - not a Raspberry Pi !

And the code you've shown is trying to use the USB peripheral within stm32f411re the chip - not the UART that's connected to the ST-Link's VCP.

PS:

And pasting that code into TeraTerm's clipboard won't do anything useful at all !!

[SofLit]

As I expected it needs to be automatically detected on Linux. I thought it would be named ttyUSB. 
Glad to know that!

[suhfi]

yes, thank you so much for the reply. And i have understood what you have said, i tried it and got the port. but my biggest concern is while using usb_device in the middleware, i am not able to send any data. like the send function which i am using is sending the blank space to the raspberry pi, so i want to know what exactly to be written in the code to send the data and the debugging process. 

[SofLit]

Which middleware?? USB device?

you dont need any middleware you just need to use the UART connected to the stlink. Nothing else!

[Andrew Neil]

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@SofLit wrote:

I thought it would be named ttyUSB. 

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I added a 2nd Nucleo board, and it appeared as  /dev/ttyACM1 

An FTDI cable gets  /dev/ttyUSB0 

Some Google hits on ACM vs USB:

https://rfc1149.net/blog/2013/03/05/what-is-the-difference-between-devttyusbx-and-devttyacmx/

https://www.reddit.com/r/linux/comments/11y07qn/what_is_the_difference_between_devttyusb_and/ 

[suhfi]

so, can you specifying me, while using usb connector we can write the code in usart to communicate raspberry pi 4 and stm32 nucleo- f411re board

[suhfi]

did you connect by usb connector, or did you connect tx of nucleo board to rx of raspberry pi and vice versa, ground to ground .

[Andrew Neil]

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@suhfi wrote:

 i have understood what you have said

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Clearly, you haven't.

The CN1 connector on the Nucleo-F411RE board connects only to the ST-Link - it does not connect to the stm32f411re microcontroller chip.

The ST-Link's VCP is connected to USART2 of the stm32f411re microcontroller chip:

Therefore, if you want to communicate via the ST-Link's VCP, you need to use USART2 of the stm32f411re microcontroller chip.

You do not use the USB within the stm32f411re microcontroller chip.

PS:

The current User Manual for the Nucleo board is unhelpful in that it doesn't clearly show the VCP connection:

This has been reported to ST, but not yet corrected:

https://community.st.com/t5/stm32-mcus-boards-and-hardware/nucleo-user-manuals-don-t-show-the-vcp-uart-connection/m-p/644959/highlight/true#M17438