USB

USB Host Controllers

Xbox hardware contains two OHCI USB Host controllers within the MCPX southbridge. The two controllers are designated USB0 and USB1. On retail consoles USB0 is connected to the 4 front panel game controller ports. Although USB1 is available, it is not enabled in retail titles and it is not mapped out of the MCPX, so it is difficult to use in homebrew.

The USB controllers are configured and accessed over MMIO. See https://xboxdevwiki.net/Memory. The memory structure follows the standard OHCI specification (OHCI Spec Table 7-1).

• USB0 is on PCI Bus 0, device 2, function 0 and is connected to IRQ1.
• USB1 is on PCI Bus 0, device 3, function 0 and is connected to IRQ9.

OHCI supports USB devices up to USB1.1 12Mbit/s. OHCI also supports Low Speed USB (1.5MBit/s) however it appears that the retail XDK host stack does support Low Speed devices.

Xbox hardware has the following specific OHCI register values set by the system firmware that may differ from the standard (Obtained from a Retail v1.6 PAL Xbox):

USB0:
HcRevision:                    0x10
HcRhDescriptorA:               0x01001204
    NumberDownstreamPorts:     4 (Four downstream ports)
    PowerSwitchingMode:        0 (All ports are powered at the same time)
    NoPowerSwitching:          1 (Ports are always powered on when the HC is powered on)    
    DeviceType:                0 (Not a compound device - always 0 for Roothubs) 
    OverCurrentProtectionMode: 0 (Over-current status is reported collectively for all downstream ports)
    NoOverCurrentProtection:   1 (No overcurrent protection supported)
    PowerOnToPowerGoodTime:    1 (2ms Power on to good time)
HcRhDescriptorB:
    DeviceRemovable:           0 (Device not removable)
    PortPowerControlMask:      0 (Power Control Mask not set) 

USB1:
HcRevision:                    0x10
HcRhDescriptorA:               0x01000202
    NumberDownstreamPorts:     2 (Two downstream ports)
    PowerSwitchingMode:        0 (All ports are powered at the same time)
    NoPowerSwitching:          1 (Ports are always powered on when the HC is powered on)  
    DeviceType:                0 (Not a compound device - always 0 for Roothubs) 
    OverCurrentProtectionMode: 0 (Over-current status is reported collectively for all downstream ports)
    NoOverCurrentProtection:   0 (Over-current status is reported collectively for all downstream ports)
    PowerOnToPowerGoodTime:    1 (2ms Power on to good time)
HcRhDescriptorB:
    DeviceRemovable:           0 (Device not removable)
    PortPowerControlMask:      0 (Power Control Mask not set) 

V1.0 Xboxes

V1.0 Xbox consoles differ in that they contain an internal 4 Port USB Daughterboard (https://xboxdevwiki.net/Motherboard#USB_Daughterboard). The daughterboard is connected to Port 1 of the OHCI Root Hub. The 4 downstream ports of the daughterboard are then fed to the 4 front panel game controller ports. In this instance Ports 2,3 and 4 on the OHCI Root Hub are not connected.

Xbox software uses a kernel export to determine which ports to use when looking for gamecontrollers. Bit 0 of export variable XboxHardwareInfo determines whether the daughterboard is present. If set, the daughterboard is present.

Port Numbering

The front gamecontroller ports are not connected sequentially to the OHCI Root Hub ports or the Daughterboard. The following port mapping applies to all Xbox revisions:

Game controller Port 1,2,3,4 are connected to 3,4,2,1 respectively of the RootHub or Daughterboard Ports.