Posted on April 25, 2013 at 12:25Ok, getting there (see below)
But just a couple of problems:
As below, I've modified the example to echo what is sent from the PC. To check reliability, I have the PC also echo, so the same message bounces forever, or should. But it all stops after 649. The message is 20 bytes, 01234567890123456789
At this time, I am still receiving messages at the stm, but send stops working (back to the PC).
I think it might be something to do with APP_Rx_ptr_in, which is reset to 0 when it gets to APP_RX_DATA_SIZE, it is always a low value (about 40) when everything stops.
Other problem: If I restart either end, it doesn't seem to work until I unplug and replug the USB cable.
Anyone know enough about the sample program to know what is happening here?
Thanks
Solution so far: It is as easy as rs232 (almost), when you know how.
From this library Clive mentioned earlier
http://www.st.com/web/en/catalog/tools/PF257882Run the VCP (virtual com port) example.At that point, if you have a usb cable plugged in, it will appear in the PC device list in Ports(COM&LPT) as ''STMicroelectronics VirtualCom Port'', and in my case on COM3.
You then just read / write to that from your PC app just like you used to with rs232.
The top level code is in usbd_cdc_vcp.c. Note that the default line coding is 115200 baud, 1 stop bit, no parity, 8 bit, I set my com port to this but it probably doesn't make any difference as it's not actually going over rs232.
If you put a breakpoint in VCP_DataRx it should trigger when you send something to STM. The project copies it out to a real rs232 port, put if you add a line ''VCP_DataTx(Buf, Len);'' you can get it to echo back to usb.
You also have to change ''VCP_DataTx;'' as it has obviously been hacked to only work with rs232 receive, like this:
int Count=0;
while (Count<Len)
{
APP_Rx_Buffer[APP_Rx_ptr_in] = *(Buf+Count)+1;
Count++;
APP_Rx_ptr_in++;
if(APP_Rx_ptr_in == APP_RX_DATA_SIZE)
{
APP_Rx_ptr_in = 0;
}
}
return USBD_OK;
