HID Packet Taking Too Long at FS USB

jvavra · ‎2014-07-27

Posted on July 28, 2014 at 01:25

I have two different projects: one based on the '205, one on the '427, Both use identical USB libraries from ST. They are both set up as FS devices using the internal USB PHY. The issue I am seeing is that in the '205 project, the function USBD_HID_SendReport (which actually just calls ''DCD_EP_Tx'') is taking ~30uS to execute (just what I'd expect). However, the project based on the '427 is taking ~600uS to send the exact same report.

What setting do I have wrong? I've done a compare/diff on the USB-related files between the two and they seem identical.

chen · ‎2014-07-28

Posted on July 28, 2014 at 10:11

Hi

''I have two different projects: one based on the '205, one on the '427, Both use identical USB libraries from ST. They are both set up as FS devices''

The STM32F4 series has a different USB driver - the OTG driver.

I did not know the USB FS driver would work on the F4 series.

I am not sure if the FS peripheral in the F4 is the same as in the F2.

Also, bear in mind that the ST USB drivers are far from perfect (they are full of bugs).

jvavra · ‎2014-07-28

Posted on July 28, 2014 at 14:32

Actually, the '205 uses the same OTG FS driver. And, as I said, the library function works fine on the '205, while the identical one doesn't work on the '427.

jvavra · ‎2014-07-28

Posted on July 28, 2014 at 19:21

I was able to narrow down that it is the macro ''USB_OTG_WRITE_REG32'' that is taking all of the time in transferring this packet. Anyone seen this before?