The Family Computer (Famicom) Keyboard to USB HID Adapter using a Raspberry Pi RP2040.
With just a RP2040 and a little bit of wiring, you can connect the Famicom's Keyboard up to any computer that accepts a standard USB HID interface. This has been tested on Windows, FreeBSD, MacOS, iPad iOS, and Android successfully. No drivers are required at all, as these and most other OSes ship with a native USB HID keyboard driver. After wiring up the keyboard adapter, this becomes entirely plug-n-play!
| RP2040 | DA15 | Name | Function |
|---|---|---|---|
| 11 | 12 | OUT0 | Row Reset |
| 12 | 11 | OUT1 | Column Select |
| 13 | 10 | OUT2 | Keyboard Enable |
| 26 | 07 | J2D1 | Data Pin 1 |
| 7 | 06 | J2D2 | Data Pin 2 |
| 6 | 05 | J2D3 | Data Pin 3 |
| 5 | 04 | J2D4 | Data Pin 4 |
| GND | 01 | GND | Ground |
| +3V | 15 | +5V | Power |
Source: https://www.nesdev.org/wiki/Expansion_port
Female DA-15 on peripheral
/\
| \
Gnd -- | 01 \
| 09 | -> /OE for joypad 2 ($4017 read strobe)
SOUND <- | 02 |
| 10 | -> OUT2 ($4016 write data, bit 2)
/IRQ ?? | 03 |
| 11 | -> OUT1 ($4016 write data, bit 1)
joypad 2 /D4 -> | 04 |
| 12 | -> OUT0 ($4016 write data, bit 0, strobe on pads)
joypad 2 /D3 -> | 05 |
| 13 | <- joypad 1 /D1
joypad 2 /D2 -> | 06 |
| 14 | -> /OE for joypad 1 ($4016 read strobe)
joypad 2 /D1 -> | 07 |
| 15 | -- +5V
joypad 2 /D0 ?? | 08 /
| /
\/
The Famicom Keyboard was designed to work with the Famicom's 5V power and signalling. The keyboard is comprised of just 3 ICs (Integrated Circuits / Computer Chips): a 4017 (Counter/Divider), a 4019 (Quad AND/OR Select Gate), and a 4069 (Hex Inverter). Each of these chips are designed to work at 5V, but have a minimum supply of 3V, the same as our RP2040. Thanks to this, we can run the entire circuit at 3V without the need for any logic level converters.
