Emulates a PCEngine multitap with up to 5 controllers. Supports 2-button, 3-button, and 6-button controller modes as well as mouse emulation. Uses three PIO state machines for timing-critical multiplexed output on Core 1.
- Wire protocol: Multiplexed parallel bus -- 4 data lines, 1 select line, 1 clock/OE line
- PIO programs: 3 state machines on PIO0:
plex.pio(sm1) -- Data multiplexing on D0-D3clock.pio(sm2) -- Monitors CLR/OE edges for scan timingselect.pio(sm3) -- Monitors SEL line for nibble toggle
- Core: Runs on Core 1 (timing-critical)
The console scans controller ports sequentially. Each scan cycle toggles the SEL line to read two nibbles per controller (buttons are split across two 4-bit reads). The CLR/OE line resets the scan to port 0.
| Pin | Signal | Description |
|---|---|---|
| 1 | VCC | 5V power |
| 2 | D0 | Data bit 0 (Up/I) |
| 3 | D1 | Data bit 1 (Right/II) |
| 4 | D2 | Data bit 2 (Down/Select) |
| 5 | D3 | Data bit 3 (Left/Run) |
| 6 | SEL | Select -- nibble toggle from console |
| 7 | CLR/OE | Clear/Output Enable -- scan reset from console |
| 8 | GND | Ground |
Pin 7 is labeled OE (Output Enable) in some references and CLR (Clear) in others. They are the same signal.
See PCEngine Protocol Reference for wire-level details.
The PCEngine controller port is 5V. RP2040 boards (Pico, KB2040, etc.) are 3.3V and their GPIOs are not 5V tolerant.
Output lines (D0-D3, adapter → console): 3.3V output is above the PCEngine's TTL high threshold (~2.0V), so these work without level shifting.
Input lines (SEL, CLR/OE, console → adapter): The console drives these at 5V. Connecting them directly to RP2040 GPIOs risks damaging the chip. Use a voltage divider on each input line:
Console (5V) ──[1kΩ]──┬── GPIO (3.3V safe)
│
[2kΩ]
│
GND
This drops 5V to ~3.3V. Use 1kΩ (top) + 2kΩ (bottom) for each of SEL and CLR/OE (2 dividers total, 4 resistors).
Alternatively, a bidirectional level shifter module (BSS138-based or TXB0106) works but is overkill for these two slow input signals.
KB2040 (default):
| Signal | GPIO | Notes |
|---|---|---|
| D0 | GP26 | Data bit 0 (consecutive out group) |
| D1 | GP27 | Data bit 1 |
| D2 | GP28 | Data bit 2 |
| D3 | GP29 | Data bit 3 |
| SEL | GP18 | Select/nibble toggle (input from console) |
| CLR/OE | GP19 | Clear/Output Enable (input from console) |
Pico:
| Signal | GPIO |
|---|---|
| D0-D3 | GP4-GP7 |
| SEL | GP18 |
| CLR/OE | GP19 |
Note: The source code uses legacy names DATAIN_PIN (GP18) for SEL and CLKIN_PIN (GP19) for CLR/OE.
- Max players: 5 (PCEngine multitap)
- Assignment: Players assigned in order of connection (first connected = Player 1)
- Persistence: Player slots persist until disconnect; no shifting on disconnect
| JP_BUTTON_* | PCEngine Button | Notes |
|---|---|---|
JP_BUTTON_B1 |
II | Primary action |
JP_BUTTON_B2 |
I | Secondary action |
JP_BUTTON_B3 |
IV (Turbo II) | Auto-fire version of II |
JP_BUTTON_B4 |
III (Turbo I) | Auto-fire version of I |
JP_BUTTON_L1 |
VI | 6-button mode only |
JP_BUTTON_R1 |
V | 6-button mode only |
JP_BUTTON_S1 |
Select | Select button |
JP_BUTTON_S2 |
Run | Start/Run button |
JP_BUTTON_DU/DD/DL/DR |
D-pad | Direct mapping |
| Mode | Constant | Buttons Active |
|---|---|---|
| 2-button | BUTTON_MODE_2 |
I, II only |
| 6-button | BUTTON_MODE_6 |
I through VI |
| 3-button (Select) | BUTTON_MODE_3_SEL |
I, II, Select |
| 3-button (Run) | BUTTON_MODE_3_RUN |
I, II, Run |
| USB Mouse | PCEngine Mouse |
|---|---|
| Left Click | Left Button |
| Right Click | Right Button |
| Movement | Movement (1:1) |
Mouse is auto-detected when a USB mouse is connected -- no manual mode switching needed.
PCEngine controllers are fully digital. Left stick input is converted to D-pad directions.
PCEngine provides no feedback channel (no rumble, no LEDs).
Profile support is available at the app level. The PCEngine output itself does not define console-specific profiles.
| App | Description |
|---|---|
usb2pce |
USB/BT controllers to PCEngine/TurboGrafx-16 |