I used my usual Atmega8 circuit with a custom firmware using the
Objective
Development AVR-USB device implementation.
Here is the core schematic. For wiring the controller, use the table below.
| I/O Micro. | #pin HD15 | Couleur | Description |
| PC5 | 1 | Brown | Column [N/A,opt,3,6,9,#] |
| PC4 | 2 | Red | Column [N/A,C,2,5,8,0] |
| PC3 | 3 | Orange | Column [N/A,B,1,4,7,*] |
| PC2 | 4 | Yellow | Column [Pause,A,East,West,South,North] |
| PC1 | 6 | Blue | Row [Pause,N/A,N/A,N/A] |
| PC0 | 10 | Black | Row [A,B,C,opt] |
| PB5 | 11 | Grey | Row [East,1,2,3] |
| PB4 | 12 | Pale Blue | Row [West,4,5,6] |
| PB3 | 13 | Pink | Row [South,7,8,9] |
| PB0 | 14 | White | Row [North,*,0,#] |
| VCC | 7 | Green | Power |
| GND | 9 | Purple | Power |
Component list:
| Ref | Description |
| U2 | Atmega8 microcontroller. ATMEGA8-16PC, ATMEGA8-16PI, ATMEGA8-16PJ or ATMEGA8-16PU. Don't use an ATMEGA8L-*, the 12Mhz clock would be too high. |
| R1 | 1.5k resistor. Ordinary carbon film 1/4 watt resistors will do. |
| R2, R3 | 68 ohm resistors. Ordinary carbon film 1/4 watt resistors will do. |
| D2, D3 | 3.6 volts zener diodes. |
| Y1 | 12 Mhz crystal. |
| C2, C3 | 18 pf capacitors. If the crystal datasheet recommends another value, use it instead. |
| C1 | 1uf capacitor. Install it near the ATmega8 power pins. |
| J2 | 6 pin header, 2.54mm spacing. Needed for programming the ATmega8. |
For the USB connection, just strip the USB cable and solder the wires directly
to the board. USB uses standard wire colors, but beware of cheap cables using
non-standard color codes.
| | Color | Description |
|---|
| | Red | +5 volts |
| | Black | Ground |
| | Green | D+ |
| | White | D- |
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