Communication between stm32 and raspberry pi4 through spi or i2c.

[suhfi]

Hello, I am doing a project with STM32F411RE NUCLEO board. I have downloaded the zip file from the web builder GRBLHAL. i have attached the file here. And I have successfully imported the zip folder onto the stm32cubeide. So for that project I want to add communication through SPI. and there is a SPI communication can be used for that project.

as in my previous query, i came to know that with UART communication, USB connector which is connected to cn1 of the board and raspberry pi USB connection - i am able to communicate. as i understood that, to communicate between raspberry pi  and stm32, i don't need to connect tx of pi -> rx of board, rx of pi -> tx of board, gnd to gnd. but can able to communicate through a connector. will that be possible with spi communication also. if no, then how can be the easy way to communicate between raspberry pi 4b and stm32f411re. and i forgot to mention that, in that file i am not able to find uart communication, i can only see the header files of spi, i2c, usb_device. can you please give me clarity over this ?

[SofLit]

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@suhfi wrote:

 as in my previous discussion i came to know that usart via usb is possible between raspberry pi and stm32 nucleo board. i am wondering if usb connector supports i2c or spi just like uart?

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No. Only UART is supported over STLINK via Virtual COMPORT. Neither SPI, nor SPI is available over STLINK.

[Andrew Neil · Accepted solution]

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@suhfi wrote:

i am talking about the usb connector?

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So why didn't you say that? You can see that there are (at least) 10 different connectors on the Raspberry Pi - how did you expect us to guess which one you meant?!

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@suhfi wrote:

i am wondering if usb connector supports i2c or spi just like uart?

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There are USB-to-I2C and USB-to-SPI converters available; eg,

I2C: 

https://ftdichip.com/products/umft201xb-01/

https://ftdichip.com/products/umft200xd-01/

SPI/I2C:

https://ftdichip.com/products/ft2232h-56-mini-module/

https://ftdichip.com/products/ft4232h-56-mini-module/

But, as @SofLit said, the Nucleo board routes neither I2C nor SPI via its ST-Link.

A standalone ST-Link V3 can route UART, SPI, and I2C

https://www.st.com/en/development-tools/stlink-v3set.html 

(not sure if that's all 3 at once, or just one at a time?)

[Andrew Neil]

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@suhfi wrote:

 i am wondering if usb connector supports i2c or spi just like uart?

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You still don't really seem to have understood what's happening in the UART case.

It's not the "USB connector" which supports UART - it's the USB-to-UART converter which does that.

In the case of the Nucleo board, that USB-to-UART converter is part of the ST-Link.

Thus, to get the same support for I2C or SPI or anything else, you need a USB-to-whatever converter.

USB-to-UART converters are very common and widely supported - other things, not so much.