USB MSC Host issues

mjscott · ‎2013-03-26

Posted on March 26, 2013 at 14:43

I'm using an STM32F105VC Z; the hardware design is about a year old and has worked fine with the exception MSC flash recognition. The MSC system software is based on the OTG 2.1 and HOST libraries and the MSC example. When I first started debugging the USB flash I was using an 8 Gig FAT32, the system would not enumerate it. Look over the code and everything looked right (verified clock speeds, I/O configuration bits, etc), tried the STM32F105/107 USB Host IAP app and got the same thing. I tried a 4 Gig FAT flash and it work perfectly. Now the system needs to work with all thumb drives, so I started debugging again. I have the original flash which still works fine, I tried another 4 Gig flash with FAT32, it will enumerate, gets into the MSC class code and will not call the user app. Tried another 4 Gig FAT32 (sent with my ST 207 development board) it will enumerate and gets stick in the MSC class code. Tried another 4 Gig FAT flash it will recognize the drive but will not enumerate it, gets stuck in the host enumeration, reads the first 8 bytes but never completes the read description. Here is where it gets really strange, if I stop the debugger in the Host Enumeration code and single step it, 1 out of ten times it will enumerate. On the drives that enumerate if I stop the code in the usbh_msc_bot code and halt it in USBH_MSC_DECODE_CSW 1 out of every ten times it will get through the class code and read the disk (all of them do this). Seems like a speed issue, verified the USB clock and everything is right. If I add a 250 msec delay in the USBH_MSC_DECODE_CSW code it will make it though msc class all the time and will read the files, all-be-it very slowly (much slower then the 4 Gig FAT flash that always worked).

Now this is where it gets a little stranger, I have another project using the STM32F207 G development board, using the ST demonstration builder code I can read any (ANY) flash drive I plug in. Demonstration builder is based on the same OTG and HOST libraries and FATFs code. It is also running FreeRTOS. When I do a file compare between the files Iâ€™m using with the F105 and the ones for the F207 they are identical.

If anyone has solved this with the F105 let me know what your experience has been.

mjscott · ‎2013-03-27

Posted on March 27, 2013 at 12:41

Problem found, you all may want to take note of this.

The errata for the STM32F105 Z silicon states a number of USB FS OTG flaws which require either a specific sequence of instructions or the avoidance of specific sequences of instructions. The ST USB OTG library is relying on the C compiler to create or avoid these sequences, big mistake.

I would recommend that ST include assembly language patches to assure that their library code actually works when dealing with flawed silicon workarounds.