We have developed a custom board based on IMX53 and we are running Android perfectly from a micro-SD Card slot we have.
Although this is fine for development, for production, we would like to flash our images to the board's eMMC (different SDIO bus than the micro-SD slot).
We are trying to get Windows to recognize our board from its USB OTG interface (mini-USB connector to the host computer). We tried Windows XP, Windows 7 and Windows 8, but all we get is an "unknown device" in the Devices Manager. We tested in a Quick Start Board, and the computer can recognize it correctly. We are clueless about what can be the cause of our problem.
We removed the bootable SD Card, plugged the board into the computer's USB and powered it on. According to the docs, IMX53 should try to find the bootloader in the SD Card and, as it is not there, it should attempt to boot from USB OTG. We tried changing the boot resistors to boot from USB by default, but that also did not help Windows to recognize the device correctly.
I am attaching the schematics we have for this circuitry.
This is our boot configuration for eMMC:
Any thoughts would be much appreciated.
1) When booting from the SD Card, we can successfully debug our board using Android Debug Bridge on Linux, using the same USB OTG connection.
2) Using an oscilloscope, we can see some communication, but it seems that it is just the PC trying to start the communication to IMX53.
3) We tried removing U111, to be sure that IMX53 is not generating a VBUS, while PC is supplying it.
4) We tried to add two 3.3kOhm resistors to USB OTG ID, as defined in the QSB reference Schematics below: