How to transmit and receive data with USB Custom HID device?

[VCapu]

I am using a custom board with a STM32F4. It seems that I can receive the data through this function that is called by interrupt and adding the pointer read_buffer, that I use inside the RxUSB() function to get the data and do the necessary operations on it.

USBD_StatusTypeDef USBD_LL_PrepareReceive(USBD_HandleTypeDef *pdev, uint8_t ep_addr, uint8_t *pbuf, uint32_t size)

{

 HAL_StatusTypeDef hal_status = HAL_OK;

 USBD_StatusTypeDef usb_status = USBD_OK;

 read_buffer = pbuf;

 hal_status = HAL_PCD_EP_Receive(pdev->pData, ep_addr, pbuf, size);

 usb_status = USBD_Get_USB_Status(hal_status);

if(usb_status == USBD_OK) 

RxUSB(); 

 return usb_status;

}

Instead I transmit using in every point I need (for example in the functions that are in the Main) the function USBD_CUSTOM_HID_SendReport(&hUsbDeviceFS, ArrayTxUSB, CODA_USB);. It's not called by an interrupt.

The problem that I am seeing is that the communication stops to work soon and sometimes I can't even transmit. Maybe this is not the right way to trasmit and receive.

Could anyone help me? I'm stuck on this problem.

[Walid ZRELLI · Accepted solution]

Hello @VCapu​,

You can refer to following example available under STM32CubeF4 package (path: Projects\STM32446E_EVAL\Applications\USB_Device\CustomHID_Standalone).

You could use this as inspiration.

BeST Regards,

Walid

[VCapu]

Now I can receive without problems inside the function USBD_StatusTypeDef USBD_LL_PrepareReceive(USBD_HandleTypeDef *pdev, uint8_t ep_addr, uint8_t *pbuf, uint32_t size) called by interrupt. Iside this function I placed my rxusb function that manage the receive buffer.

For the transmission, I see that not all the messages sent works, maybe I should use also a transmission called by interrupt. How could I do it? Thank you very much.

[Walid ZRELLI]

Hello @VCapu​ ,

You could reuse the same method from the example I sent you.

Indeed, the transmission was done in the USBD_CUSTOM_HID_SendReport() function, and you mentioned that you implemented it in the interrupt.

So it should work fine for you.

Try to reproduce the same process as in the example. 

BeST Regards,

Walid

[VCapu]

Thank you. I am using for transmission the function USBD_CUSTOM_HID_SendReport(&hUsbDeviceFS, ArrayTxUSB, CODA_USB); but without interrupt.

Where I should put this function to transmit through interrupt? And how should I enable this interrupt? Which is the event that triggers it?

[Walid ZRELLI]

It depends on your application.

In fact, in our example we use the potentiometer of the STM32446E-EVAL board to transfer the result of the converted voltage

 (via the ADC) the to the PC host (these values are sent to the PC using the endpoint1 IN) , so you will find USBD_CUSTOM_HID_SendReport() function called in the ADCx_DMA_IRQHandler() function.

Try to go into the details of the example and you will have all the information you need.