USB STM32F407 VCP Bidirectional communication bare metal?

[waldi]

I'm sending a continuous data stream from uC to PC via VCP which is implemented as CDC. During stream every responded IN token for EP1 generates DIEPINT_XFRC, so I'm seeing interrupts:

DIEPINT_XFRC

DIEPINT_XFRC

DIEPINT_XFRC

...

Now I send something to uC and get these interrupts:

  1. GINTSTS_RXFLVL (GRXSTS_PKTSTS_OUT_DATA_RECEIVED)

  2.GINTSTS_RXFLVL (GRXSTS_PKTSTS_OUT_TRANSFER_COMPLETED)

  3. GINTSTS_OEPINT (DOEPINT_TRANSFER_COMPLETED)

thereafter again, the stream to PC

...

DIEPINT_XFRC

DIEPINT_XFRC

...

But sometimes (I thing if the OUT token is received at some wrong uC USB stage) i get:

  1. GINTSTS_RXFLVL (GRXSTS_PKTSTS_OUT_DATA_RECEIVED)              //ok

  2. GINTSTS_RXFLVL (GRXSTS_PKTSTS_OUT_TRANSFER_COMPLETED) //ok

  3. GINTSTS_OEPINT (DOEPINT_TRANSFER_COMPLETED)                     //ok

  4. GINTSTS_RXFLVL (SETUP_DATA_PACKET_RECEIVED)

  5. GINTSTS_RXFLVL (SETUP_COMPLETED)

  6. GINTSTS_OEPINT (USB_REQUEST_CLEAR_FEATURE) <---

Why clear feature? It seems that the core is not acknowledging the last OUT transfer and PC tries to reset the device.

With limited transmission blocks from uC to PC:

send command from PC to uC-> receive data block

send command from PC to uC-> receive data block

...

everything is working fine.

[Pavel A.]

Please look at this thread. Does it resemble your situation?

https://social.msdn.microsoft.com/Forums/en-US/b61dad9b-48f7-4eca-ab56-3c2ee92d62fa/windows-10-usbsersys-has-a-bug-it-corrupts-data-how-can-i-report-it-and-how-can-i-demonstrate-it

-- pa

[waclawek.jan]

What exactly is the content of the Setup packet arriving in 4.-6.?

JW

[waldi]

bmRequest     2   

bRequest       1   

wValue       0   

wIndex      129   

wLength       0   

[waldi]

@Pavel A.​ 

I don't know how to change "usbser.sys" to "winusb.sys", thus cannot test. But the error description seems very similar.

[Pavel A.]

Usbser and winusb are very different, one can just change one to the another. If you have similar issue with winusb, please report on the MSDN forum.

Regards,

Pavel A.

[waclawek.jan]

So it's CLEAR_FEATURE on the *IN* endpoint 1 of the ENDPOINT_HALT feature.

IMO the host (PC) sees IN EP1 returning STALL on IN tokens, so it attempts to clear the HALT state of that endpoint.

JW

[waldi]

It seems that there are 0x40 bytes missing in the last transfer so the host resets the endpoint.

[waldi]

Packet count is 1, that means one packet is still not emitted? It would explain 0x40 difference.

[waldi]

The mess starts if the OUT interrupt with 5 chars from PC is coming in during buffer load:

for (uint32_t i = 0; i < words_to_write; i++){
	*(USB).DFIFO[1]=USB_buffer[i];
}

I've deactivated OTG_FS_IRQn interrupt before load and activated it directly after - now the bidirectional data transfer is stable.

Hope this will help someone else!)