The USB Gecko is a Wii/Gamecube development and hacking tool which connects to the USB port of the computer, and to the GameCube memory slot of the Wii. It can be used to upload homebrew, to use your computer as a remote terminal under Wii Linux and as a remote debugging tool. For more information see the USB Gecko homepage. It has recently been discontinued and the schematics released on Google code. A snapshot of the code tree is here.
See Gecko OS for the Hombrew application to launch a game and be able to debug it remotely using this device.
Windows Side Application Programming
Linux Side Application Programming
The USB Gecko will usually be recognized as a USB to serial port converter and a device file of the form /dev/ttyUSB0 will appear. Simply writing to and reading from this device file will send data across the USBGecko link.
Failing that, userspace tools could use the libusb library and usb_bulk_write and usb_bulk_read functions. The USBGecko will appear as 0403:6001 in the lsusb output.
The USB Gecko is a two step converter to convert EXI<->serial<->usb. It is a fancy serial port. All the fun is provided by software. The EXI interrupt cannot be triggered from the PC because the pin on the Wii side is left unconnected. In theory one could open up the USB Gecko and run a trace from that pin to one of the many unused pins on the CPLD, reprogram the CPLD, and be able to trigger the EXI interrupt from the PC side. This can be seen in the image at right.
The pins on the bottom connector are numbered from left to right 12 down to 1, even numbers being on the bottom row, odd numbers being on the top row. Pin 3 is the EXI interrupt pin, which is unconnected for some unknown reason.
The pins on the front side are what connect to the Wii EXI port. The pins on the back side connect to the Altera CPLD's JTAG pins for programming. The pins are, in order from left to right (matching the bottom picture at right):
TDO, 3.3V, TMS, TDI, TCK, GND.
The Gecko has 3 chips:
- The USB interface is provided by the FT245RL which converts USB to two 8 bit bidirectional FIFOs. One sends data to the Wii (128 byte capacity), the other receives data from the Wii (256 byte capacity).
- The FIFOs are connected to an ALTERA CPLD (Complex Programmable Logic Device) EPM570T100C5N which converts the parallel data to the serial datastream needed for the Wii's EXI port.
- There is a 512K byte flashrom, the SST39VF040 which is accessable only on the Wii side through the Altera CPLD. This is not strictly necessary for the USB Gecko's main functionality.
USB Gecko schematics (BSD licensed). The archive doesn't actually contain a schematic of the circuit, but rather the files needed for producing the circuit boards and some source code. The VHDL source for the CPLD itself is included.