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Nucleo-H743: Trouble setting VCP into operation on USB FS

Question asked by Torsten Aurich on Nov 28, 2017

Hello Community,


as written in my last post (See here) i try to set VCP into Operation
on a Nucleo-H743ZI. Now i'm on the stage to set communication into operation.
After establishing connection to Win10 "hUsbDeviceFS.dev_state" goes
to 3 (USBD_STATE_CONFIGURED). This is the startpoint in my firmware to
try to send data to Host. For this i'm using the usb cdc interface function


uint8_t CDC_Transmit_FS(uint8_t* Buf, uint16_t Len).


On the Host side i'm using HTerm0.8.1Beta. If i start HTerm but do not open
connection to the COM Port to H7x my software recognise this because
CDC_Transmit_FS returns USBD_BUSY. If i open the COM Port in HTerm then
my firmware transmit data to Host (under certain circumstances).
Now i found out, if the size of data that i will be transfered is
lager than 24 Bytes, the HTerm tells me something like this:


...can't open COM Port because of internal error


Did anyone have experience with a behavior like this?

Any Remarks?


Kind Regards