USB Data Transfer with STM32L552E-EV

[Nirene]

Greetings,

Kindly, I would like to know which USB interface I can use to transfer data between the STM32L552E-EV and the reComputer J4012.

I am working with TEE, and my goal is to send plaintext from the reComputer to the STM32L5 so that it can be encrypted on the device. However, when I send data, I do not receive any response.

I have tried using both the USB port and ST-Link, but the result is the same. I can see the ST-Link device on the reComputer, but when I use USB CDC, it is not recognized.

Could you explain the proper USB connection and how to set up the communication?

[mƎALLEm]

Hello,

The connection (CN22) of STLINK over a virtual comport (windows)  offers a kind of "UART protocol over USB".

If you need to use the USB you need to use CN1 connector (USB FS).

[Andrew Neil]

Some more detail would help:

How to write your question to maximize your chances to find a solution

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@Nirene wrote:

the reComputer J4012.

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You mean this: https://files.seeedstudio.com/wiki/reComputer/reComputer-J40.pdf ?

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@Nirene wrote:

I am working with TEE,

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What do you mean by that?

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@Nirene wrote:

However, when I send data, I do not receive any response.

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So what, exactly, did you try?

As @mƎALLEm said, the ST-Link provides a Virtual COM Port (VCP); for native USB, you would use CN1.

For the VCP, you just need to use the STM32L5 UART on whichever of the STM32L5's pins is connected to the VCP - see the board's User Manual for details.

For native USB, you would have to make a complete USB device implementation.

CubeMX will give you access to examples...

PS:

The STM32L552E-EV also has an RS232 port, so you could use a USB-to-RS232 adaptor;

There are also logic-level UART signals available on the PMOD and STMOD+ connectors, so you could use a UART-to-USB adaptor (of the appropriate voltage) there.

These will also give you a VCP.

[Andrew Neil]

From the User Manual:

[Nirene]

Hello
Thank you for your explanation.

Currently, I am using the CN1 port for USB FS, but I am still facing an issue. When I connect the board to the reComputer J4012, the USB cable is detected physically, but no USB device (CDC) appears on the reComputer side. So when I try to write commands, I cannot see any USB interface to communicate with.

Could you please advise what additional configuration is required on the STM32L552 (CubeMX / firmware side) so that the CN1 USB FS is enumerated correctly as a CDC device on the host?

Thank you for your support.

[Nirene]

Hello,

Thank you for the explanation and help.

Yes, I am using the reComputer-J4012 board as shown in your reference:
https://files.seeedstudio.com/wiki/reComputer/reComputer-J40.pdf

Here is what I have tried so far:

• I connected the CN1 USB FS port from the STM32L552E-EV to the reComputer J4012 USB host.

• I also tried using the ST-Link VCP (CN22) connection.

With ST-Link, the reComputer can detect it correctly, but I cannot send any data to stm32l5 and receive a response. However, when I use the CN1 USB FS port, although the cable is connected, the reComputer does not enumerate any USB CDC device from the STM32L5, so I cannot send commands or data.

My goal is to work with TEE (Trusted Execution Environment): I have created an encryption key inside the TEE on the STM32L5, and I want to send data from the reComputer so that the STM32L5 can encrypt it inside the TEE.

You mentioned:

“For native USB, you would have to make a complete USB device implementation.”

Could you please point me to a guide, reference manual, or example project that shows how to properly implement a USB CDC device on the STM32L552 (for example using Cube MX), so that it is recognized by the host?

Thank you very much for your support.

[mƎALLEm]

So that's a USB stack related question. It was moved to STM32 MCUs Embedded software forum board.

[FBL]

Hi @Nirene 

To proceed you need to narrow down the issue, and test simple communication with your laptop. Here is an example using STM32CubeL5/Projects/STM32L552E-EV/Applications/USB_Device/CDC_Standalone

[Andrew Neil]

Getting a native USB connection working is significantly more complex that a simple UART connection.

It should be easier to pursue getting the ST-Link (or other VCP) connection working ...