Customer use AM3517-WinCE6 platform to play MPEG4 media file, they use two kind of storage to store media file, one is SD card, another is U-Disk. By using U-Disk, when playing some high bit stream media file, the U-Disk is easy to break, and the votage of USB vbus is 0 after measurement, after reboot it will recover. By using SD card, there is no this problem.
When play the high bit stream media file, the read file operation is more frequently, so is this issue related to the USB transfer mode(interrupt, bulk, isochronous )? please help to have a check, thanks a lot!
First guess would be that long transfers from your U-Disk somehow put the 5V VBUS provider to overcurrent which will shut down for protection. Is you customer using EHCI with a USB3320 PHY for plugging the U-Disk? What chip is used for generating the 5V and how much maximum current is it advertised to provide?
A good test would be to try with another U-Disk (a branded one, we could expect it to be more power efficient) or check for the possibility of using a higher current voltage provider for the VBUS.
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Customer use the AM3517 EVM board USB host port, this USB host use EHCI with a USB3320 PHY , the VBUS is provide by USB phy and external 5V parallel. So is it possible that USB PHY disable itselt when overcurrent?
The PHY does indeed have an overcurrent detection mechanism that will shut down the 5V generation if the U-Disk draws too much power. The fact that you measure no voltage after the issue happens seems to be a good clue that this might be the problem.
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