Thanks for the tip - pin 137 was being pulled up when the cable was plugged in. In this condition, on the PC side, the error (obtained via UsbView) was DeviceFailedEnumeration: Unknown USB Device (Device Descriptor Request Failed). The device descriptor request was repeated infinitely, which I’m guessing was due to the SoC also being in host mode.
After some resoldering to pull pin 137 low, there’s no detection at all on the PC side.
USB OTG settings are:
[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\USBOTG]
"Dll"="otg_vybrid.dll"
"IClass"=hex:7b,41,33,32,39,34,32,42,37,2d,39,32,30,43,2d,34,38,36,62,2d,42,30,\
45,36,2d,39,32,41,37,30,32,41,39,39,42,33,35,7d,00,00
"Priority256"=dword:00000064
"HCDPortNumberOnOTG"=dword:00000001
"DisableRoleSwitch"=dword:00000000
"InitialRoleMaster"=dword:00000001
"DynamicClientLoad"=dword:00000003
"Order"=dword:00000020
"Index"=dword:00000000
"Prefix"="OTG"
[HKEY_LOCAL_MACHINE\Drivers\BuiltIn\USBOTG\UsbFn]
"OTGSupport"=dword:00000000
"IClass"=hex(7):7b,00,45,00,32,00,42,00,44,00,43,00,33,00,37,00,32,00,2d,00,35,\
00,39,00,38,00,46,00,2d,00,34,00,36,00,31,00,39,00,2d,00,42,00,43,00,35,00,\
30,00,2d,00,35,00,34,00,42,00,33,00,46,00,37,00,38,00,34,00,38,00,44,00,33,\
00,35,00,7d,00,3d,00,25,00,62,00,00,00,7b,00,36,00,46,00,34,00,30,00,37,00,\
39,00,31,00,44,00,2d,00,33,00,30,00,30,00,45,00,2d,00,34,00,34,00,45,00,34,\
00,2d,00,42,00,43,00,33,00,38,00,2d,00,45,00,30,00,45,00,36,00,33,00,43,00,\
41,00,38,00,33,00,37,00,35,00,43,00,7d,00,3d,00,25,00,62,00,00,00,00,00
"BusIoctl"=dword:002a0048
"OTGGroup"="01"
"Priority256"=dword:00000064
"Irq"=dword:0000006b
"MemLen"=dword:00001000
"MemBase"=dword:40034000
"Order"=dword:00000002
"Index"=dword:00000001
"Dll"="usbfn.dll"
"Prefix"="UFN"
and function driver settings are:
[HKEY_LOCAL_MACHINE\Drivers\USB\FunctionDrivers]
"DefaultClientDriver"="Mass_Storage_Class"
[HKEY_LOCAL_MACHINE\Drivers\USB\FunctionDrivers\Mass_Storage_Class]
"DeviceName"="RAMDisk"
"idProduct"=dword:0000ffff
"bcdDevice"=dword:00000000
"Product"="Generic Mass Storage (PROTOTYPE--Remember to change idVendor)"
"Manufacturer"="Generic Manufacturer (PROTOTYPE--Remember to change idVendor)"
"idVendor"=dword:0000045e
"FriendlyName"="Mass Storage"
"InterfaceProtocol"=dword:00000050
"InterfaceSubClass"=dword:00000006
"Dll"="usbmsfn.dll"
Any ideas?