We have a customized board using OMAP-L138 processor. A usb board is connected to the OMAP board through VBUS, DRVBUS, PM, PD and ID lines. The USB ID pin is grounded so that the USB will be put into HOST mode. The usb board is powered by an external 5v power pump which is controlled by DRVUSB line from the OMAP, An external 20MHz clock is used. The usb board worked in the past in both u-boot mode and kernel mode. Then we built a new usb board which has the 20MHz clock on it. We tested our OMAP board with the new usb board. The new usb board failed. Then we went back to test the old usb board. The old usb board also failed. I did the test in both u-boot mode and kernel mode. usb interrupt register showed VBUS_ERROR . I printed out the register values in u-boot mode and saw the USB0VBUSSENSE bit never got set during 100ms VBUS detection period. The USB device register showed the USB went into A device, but it couldn't go to HOST mode. VBUS valid bits are not set.
The oscilloscope showed the VBUS line did rise to 5v on the OMAP side in 4ms after DRVBUS line went high. Why couldn't the PHY detect voltage on VBUS line? The following output showed register values in the while loop of checking whether the USB goes to HOST mode. It seems the USB voltage comparator doesn't work at all because USB0VBUSSENSE bit in devctrl register is always zero. What could be the problem? Could the new usb board cause any damage to the OMAP board? or something else?
Devctl: 0x81, cfgchip2:0x20972, B device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x81, cfgchip2:0x20972, B device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x81, cfgchip2:0x20972, B device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x81, cfgchip2:0x20972, B device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x81, cfgchip2:0x20972, B device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x1, cfgchip2:0x20972, A device
PHY is not sensing voltage presence on the VBUS pin
Devctl: 0x80, cfgchip2:0x20972, B device
PHY is not sensing voltage presence on the VBUS pin
Session is cleared
Thanks
Jie