# Mouse Pointer Hardware

This folder contains source files and notes for the ClickTapToe mouse pointer
PCB.

The mouse pointer board contains the optical pointing sensor and connects to the
input hub over RJ45.

The initial KiCad source for this board is derived from the PMW3610 breakout by
`siderakb/pmw3610-pcb`. The current ClickTapToe revision preserves the original
PMW3610 optical/lens/LDO section while adding the project-specific RJ45 cable
interface.

Mouse Pointer 1.0 is the first ClickTapToe-maintained production revision of
this board.

## RJ45 Pinout

The connector is an 8P8C modular jack used for ClickTapToe sensor wiring. It is
not Ethernet.

| RJ45 pin | Signal | Notes |
| --- | --- | --- |
| 1 | `VIN` / `3V3` | Sensor board input power |
| 2 | `GND` | Ground return |
| 3 | `SCLK` | PMW3610 SPI clock |
| 4 | `SDIO` | PMW3610 bidirectional SPI data |
| 5 | `nCS` | PMW3610 chip select |
| 6 | `GND` | Ground return paired with `SCLK` |
| 7 | `MOTION` | Active-low PMW3610 motion output after local series resistor |
| 8 | `nRESET` | Reset routed from the input hub through a 0 ohm link |

Twisted pair grouping:

| Pair | RJ45 pins | Signals |
| --- | --- | --- |
| Pair 1 | 1-2 | `VIN` / `3V3` + `GND` |
| Pair 2 | 3-6 | `SCLK` + `GND` |
| Pair 3 | 4-5 | `SDIO` + `nCS` |
| Pair 4 | 7-8 | `MOTION` + `nRESET` |

## Board Configuration

- Default logic configuration is 3.3 V: `JP1` is a 0 ohm link from `VIN` to
  `VDDIO` and is installed by default.
- Alternate 1.8 V logic is available by populating `JP2`, a 0 ohm link from
  `+1V8` to `VDDIO`. `JP2` is DNP by default.
- `JP3` is a 0 ohm reset link from RJ45 `nRESET` to PMW3610 `nRESET` and is
  installed by default.
- `R3` is a 100 ohm series resistor on `MOTION`, placed near the PMW3610 side
  before the signal leaves the board.
- `R2` is a 100k optional `nCS` pull-up to `VDDIO` and is DNP by default.
- `J1` remains as a debug/test header on the PMW3610-side signals.
- `U3` and `U4` are TPD4E05U06DQAR ESD protection arrays on the RJ45-facing
  cable signals.

The RJ45 connector is unshielded and is intended for hand installation. `J1` is
also optional/test-only and is not assigned a JLCPCB part number in the
production BOM.

The current firmware handles `MOTION` on XIAO `D7` through RJ45 pin 7 and
pulses `nRESET` on XIAO `D6` through RJ45 pin 8 before PMW3610 initialization.

## Online Review

`kicanvas.html` embeds the schematic and PCB in KiCanvas for browser-based
review. If GitHub Pages is enabled from the repository root, the mouse pointer
viewer is available at:

```text
https://mazzorella.github.io/ClickTapToe/hardware/mouse-pointer/kicanvas.html
```

## Planned Layout

- `kicad/` for KiCad project source files
- `production/` for generated Gerbers, drill files, BOMs, and placement files