I have a design with a SM320DM6446AZWTA where I am getting a strange USB error on about 3% of our cards. The USB port is running in master mode.
As I increase the DaVinci temperature from about 20C to about 50C the voltage on the USB_DM and USB_DP pins climbs with temperature to 1.2V. Cooling and heating the DaVinci lowers and raises the voltage on those pins respectively. As the temperature/voltage increases the DaVinci can no longer recognize a thumb drive being inserted. When the DaVinci is warm, you can install a USB thumb drive, hit the DaVinci with a short burst of freeze spray and it will suddenly recognize the USB drive and communicate with it.
If you have a thumb drive installed, you can heat the DaVinci up to any temperature and it will continue working. If you remove it after the DaVinci is warm it does not recognize it when you reinstall it. You can perform a large number of insert/remove cycles while cool without any issues so I don't belive this is a software error.
I've dumped the USB registers when warm and cool and they are identical.
Mike Talbot
