Thursday, June 11, 2009

USB Client in Sleep mode for PXA

On resuming from sleep mode of PXA27X, the usb client wont be working straight away. No insertion events will be detected and the device will be shown as an uknown device in PC.

For overcoming this situation, we have to clear the OTGPH bit in PSSR (Power Manager Sleep Status Register). This is a write to clear bit.

OTGPH will be set when entering sleep mode when writing the PWRMODE register and indicates that the OTG pad is retaining state. So after resuming, the USB OTG, UDC and UHC should be configured, then only clear the OTGPH bit.

Referece : Marvell PXA27X Processor Developer Manual, November 3 , 2006