# SN-L00 Latency Tester

Eurorack module for measuring round-trip latency in audio/CV signal chains.

**Organization**: [SubModular](https://git.sub-net.at/submodular) / Sub-Net e.U.

## Features

- Measures latency from 0.01ms to 999ms
- 128×32 OLED display showing milliseconds
- Three modes: Single shot, Continuous, Statistics
- Skiff-friendly depth (<25mm)
- USB serial output for logging

## Specifications

| Parameter | Value |
|-----------|-------|
| Width | 8 HP (40mm) |
| Depth | <25mm |
| Power +12V | ~25mA |
| Power -12V | 0mA |
| Resolution | 0.01ms |
| Output | 0-3.3V trigger |
| Input | 0-10V tolerant |

## Project Structure

```
SN-L00/
├── hardware/
│   ├── BOM.md              # Bill of materials with LCSC part numbers
│   ├── kicad/              # KiCad schematic and PCB
│   │   ├── SN-L00.kicad_pro
│   │   ├── SN-L00.kicad_sch
│   │   ├── SN-L00.kicad_pcb
│   │   ├── README.md       # ASCII schematic reference
│   │   └── PCB_LAYOUT.md   # Placement guide
│   └── panel/
│       ├── PANEL_SPEC.md   # Dimensions and specifications
│       └── SN-L00_panel.svg # Panel design
├── firmware/
│   ├── CMakeLists.txt      # Pico SDK build
│   ├── README.md           # Build instructions
│   ├── include/            # Header files
│   └── src/                # Source files
└── docs/
    └── DESIGN.md           # Technical design document
```

## Hardware

### Components

| Part | Description |
|------|-------------|
| MCU | RP2040-Zero (Waveshare) |
| Display | 0.91" OLED 128×32 I2C |
| Output buffer | 74LVC1G17 Schmitt trigger |
| Input buffer | MCP6001 op-amp |
| Regulator | AMS1117-3.3 LDO |

Full BOM with LCSC part numbers in [hardware/BOM.md](hardware/BOM.md).

### PCB Layout (KiCad 8)

1. Open `hardware/kicad/SN-L00.kicad_pro`
2. Update PCB from schematic: **Tools → Update PCB from Schematic** (F8)
3. **Automated routing** (from terminal):
   ```bash
   cd hardware/kicad
   python3 scripts/autoroute.py
   ```
   This places components, routes, and runs DRC automatically.

   Or manually in KiCad Scripting Console:
   ```python
   exec(open('scripts/autoroute_full.py').read())
   ```
5. Fill zones: Press **B**
6. Run DRC: **Inspect → Design Rules Checker**
7. Export Gerbers: **File → Fabrication Outputs → Gerbers**

### Manufacturing

- PCB: 2-layer, 40×100mm (8HP)
- Assembly: PCBWay or similar (SMD parts)
- Hand-solder: RP2040-Zero module, OLED module
- Panel: Aluminum or PCB (8HP, 40.30×128.50mm)

## Firmware

Built with Raspberry Pi Pico SDK.

```bash
export PICO_SDK_PATH=/path/to/pico-sdk
cd firmware
mkdir build && cd build
cmake .. && make
```

Flash `sn_l00.uf2` via USB bootloader.

See [firmware/README.md](firmware/README.md) for details.

## Usage

1. Connect **TRIG OUT** to your signal chain input
2. Connect your signal chain output to **RETURN IN**
3. Press button to measure latency
4. Long press to toggle continuous mode

### Modes

- **SINGLE**: Press to measure once
- **CONT**: Auto-measures every 500ms, shows live reading
- **STATS**: Shows min/max/average after continuous mode

## Typical Latency Values

| Source | Expected Latency |
|--------|------------------|
| Analog modules | <0.1ms |
| Digital Eurorack (DSP) | 1-5ms |
| Audio interface round-trip | 3-20ms |
| DAW + plugins | 5-50ms+ |

## License

TBD

## Links

- Repository: https://git.sub-net.at/submodular/SN-L00
- Organization: https://git.sub-net.at/submodular
- Parent: [Sub-Net e.U.](https://sub-net.at)