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Add KiCad schematic and updated BOM

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Schematic includes:
- Power section: SS14 reverse protection, AMS1117-3.3 LDO
- RP2040-Zero and OLED module headers
- Trigger output: 74LVC1G17 Schmitt buffer
- Return input: voltage divider, BAT54 clamps, MCP6001 buffer
- Button with pull-up, power LED

BOM updated with correct parts and LCSC numbers.
ASCII schematic reference in hardware/kicad/README.md.
This commit is contained in:
Florian Berthold
2026-01-23 03:30:30 +01:00
parent d103b2732c
commit f100eb23bf
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hardware/kicad/README.md
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# SN-L00 KiCad Project
## Schematic Overview
```
+12V (from Eurorack)
│
▼
┌─────────────────────────────────────────────────────────────────┐
│ POWER SECTION │
│ │
│ J1 (2x5) D1 (SS14) U1 (AMS1117-3.3) │
│ Eurorack ──────►Schottky──┬────►LDO────────────► +3.3V │
│ Header protection │ │ │
│ C1 C2,C3 │
│ 10uF 10uF+100nF │
│ │ │ │
│ GND GND │
└─────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────┐
│ MCU & DISPLAY │
│ │
│ MOD1 (RP2040-Zero) MOD2 (OLED 128x32) │
│ ┌─────────────┐ ┌──────────┐ │
│ │ 3V3 5V │ │ GND │ │
│ │ GND GND │ │ VCC │◄── +3.3V │
│ │ GP0 GP9 │──SDA───────────►│ SDA │ │
│ │ GP1 GP8 │──SCL───────────►│ SCL │ │
│ │ GP2 GP7 │──TRIG_OUT └──────────┘ │
│ │ GP3 GP6 │──RETURN_IN │
│ │ GP4 GP5 │──BTN │
│ │ GP29 3V3 │ │
│ │ GND GND │ │
│ └─────────────┘ │
└─────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────┐
│ TRIGGER OUTPUT │
│ │
│ GP2 ────► U2 (74LVC1G17) ────► R3 (100Ω) ────► J2 (TRIG OUT) │
│ Schmitt buffer current limit 3.5mm jack │
│ │ │
│ C4 (100nF) to GND │
└─────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────┐
│ RETURN INPUT │
│ │
│ J3 (RETURN) ──► R4 (10K) ──┬──► R5/R6 divider ──► U3 ──► GP3 │
│ 3.5mm jack protection │ (10K/22K = 0.69x) MCP6001 │
│ │ buffer │
│ ├── D3 to +3.3V (clamp high) │
│ └── D4 to GND (clamp low) │
│ BAT54 Schottky │
└─────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────┐
│ BUTTON │
│ │
│ +3.3V ──► R1 (10K) ──┬──► GP4 │
│ pull-up │ │
│ SW1 ──► GND │
│ tactile │
└─────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────┐
│ POWER LED │
│ │
│ +3.3V ──► R2 (1K) ──► D2 (Green LED) ──► GND │
└─────────────────────────────────────────────────────────────────┘
```
## RP2040-Zero Pinout Reference
```
┌─────────────────┐
5V ──┤ 5V 3V3 ├── 3.3V
GND ──┤ GND GND ├── GND
GP29 ──┤ GP29 GP0 ├── I2C SDA → OLED
GP28 ──┤ GP28 GP1 ├── I2C SCL → OLED
GP27 ──┤ GP27 GP2 ├── TRIG_OUT → 74LVC1G17
GP26 ──┤ GP26 GP3 ├── RETURN_IN ← MCP6001
GP15 ──┤ GP15 GP4 ├── BTN (active low)
GP14 ──┤ GP14 GP5 ├── (spare)
└─────────────────┘
USB-C on bottom
```
## Files
- `SN-L00.kicad_pro` - KiCad project file
- `SN-L00.kicad_sch` - Schematic (open in KiCad 8+)
- `SN-L00.kicad_pcb` - PCB layout (to be created)
## Design Notes
### Power
- Single +12V rail used (no -12V needed)
- AMS1117-3.3 LDO provides 3.3V for MCU and peripherals
- SS14 Schottky for reverse polarity protection
- Total current draw ~20-30mA
### Trigger Output
- 74LVC1G17 provides clean Schmitt-trigger buffered output
- 100Ω series resistor for short-circuit protection
- Output: 0-3.3V (compatible with most Eurorack gate inputs)
### Return Input
- Handles 0-10V Eurorack signals safely
- 10K/22K voltage divider scales to ~0-3.1V
- Schottky clamp diodes protect against overvoltage
- MCP6001 rail-to-rail op-amp buffers signal
- Threshold set in firmware (~1.5V default)
### I2C
- 400kHz I2C to OLED display
- No external pull-ups needed (internal to OLED module)
## Opening the Project
1. Install KiCad 8.0+
2. Open `SN-L00.kicad_pro`
3. Schematic editor opens automatically