V-USB Joystick

This uses V-USB to implement a USB joystick with minimal code. It supports up, down, left, right and three buttons (and can trivially handle 5 more).

The code runs on 12MHz (external quarz) atmega8 chip. I use the usb 5V atmega power supply and two 3.6V Z-Diodes vusb work around for D+ and D-

Building

The makefile is for a usbASP programmer.

make
make flash
make fuse

Hardware

Pinout and Controls (connect to GND to press):

USB D+           PD2   !!!
USB D-           PD3   !!!
Up                PC4
Down              PC5
Left              PC3
Right             PC2
Button 1         PC1
Button 2         PC0
Button 3         PD7  !!!
5V+               VCC
GND               GND
Act LED+330 Ohm   PB0

Operation

V-USB implements a low-speed USB device in software. When connected, it tells the host that it's a USB joystick. It also tells the host what controls it has and the format of the report it sends (usbHidReportDescriptor[] in main.c). Then when the joystick changes it sends the new state of the controls to the host. This can only be done every 8ms (1/125 second), when the host asks the device if it has any updates. There are ways to make the host check more often (up to 1000 times a second) by changing its hid polling rate.

Code Base

by Shay Green with LGPL