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Is there a simple example how to combine USB CDC device and FreeRTOS ?

L_Kopp
Associate II

I am trying to implement a cdc device and would also like to use the FreeRTOS. For code generation I use CubeMX. To keep the interrupt of the receives as short as possible I want to send the answer to the host using a task. But after a few seconds my host receive an invalid answer. Is there a simple example that shows how to combine the UBS Device library with FreeRTOS ?

Regards,

Lena

9 REPLIES 9
Javier1
Principal

I have tried this before, handling the data to be sent via usb with freertos queues.

Creating a high priority not preemptable task, i still got missing USB frames ...

>>But after a few seconds my host receive an invalid answer

Sounds similar to what happened to me.

we dont need to firmware by ourselves, lets talk
gbm
Lead III

Either call Transmit only from the interrupt routine of the same priority as USB interrupt or at least disable the interrupts before calling Transmit an re-enable them immediately after.

My STM32 stuff on github - compact USB device stack and more: https://github.com/gbm-ii/gbmUSBdevice
L_Kopp
Associate II

Thanks for your answers!

I tried to start the receive in the transmit complete callback but this does not improve the behavior.

mohamed.ayed
ST Employee

Hi @Community member​ 

You Can use AzureRTOS USBX middleware it works in RTOS (Threadx) and standalone mode.

You can refer to this example:

https://github.com/STMicroelectronics/x-cube-azrtos-h7/tree/main/Projects/NUCLEO-H723ZG/Applications/USBX/Ux_Device_CDC_ACM

L_Kopp
Associate II

@mohamed.ayed​ thank you for your answer.

Since my whole project is based on freeRTOS I don't want to change the operating system. Can the procedure be applied to freeRTOS ?

Use other vendor's USB library that can be ported to FreeRTOS natively or via CMSIS-RTOS wrapper. It likely costs something, but your time isn't free either.

Do you have an example of a good USB library I tried tinyusb but it doesnt work well

Segger?

Piranha
Chief II

> I tried tinyusb but it doesnt work well

It does work. Integrate and use it properly.