Wiring Guide¶
Detailed wiring diagrams and pin connections for all SpoolBuddy components.
System Architecture¶
SpoolBuddy uses two microcontrollers:
- CrowPanel (ESP32-S3) - Display, UI, and scale (NAU7802)
- Raspberry Pi Pico - NFC reader (PN5180)
┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐
│ CrowPanel │ │ Raspberry Pi │ │ PN5180 │
│ ESP32-S3 │ │ Pico │─SPI──│ NFC │
│ │ │ │ │ │
│ UART1-OUT ────┼──I2C─│ │ └─────────────────┘
└────────┬────────┘ └─────────────────┘
│ I2C
┌────┴────┐
│ NAU7802 │
│ Scale │
└────┬────┘
│
┌────┴────┐
│Load Cell│
└─────────┘
Safety First¶
- Always disconnect power before making wiring changes
- Use 3.3V only for the PN5180 (5V will damage it!)
- Double-check connections before powering on
Wiring Diagram¶
NAU7802 Scale → CrowPanel (I2C)¶
The scale ADC connects to the CrowPanel's UART1-OUT header.
UART1-OUT Header Pinout¶
┌──────┬──────┬──────┬──────┐
│ Pin1 │ Pin2 │ Pin3 │ Pin4 │
│IO19 │IO20 │ 3V3 │ GND │
│ SDA │ SCL │ VCC │ GND │
└──────┴──────┴──────┴──────┘
NAU7802 Connections¶
| NAU7802 Pin | CrowPanel | Header | Wire Color |
|---|---|---|---|
| SDA | IO19 | UART1-OUT Pin 1 | Yellow |
| SCL | IO20 | UART1-OUT Pin 2 | White |
| VCC | 3.3V | UART1-OUT Pin 3 | Red |
| GND | GND | UART1-OUT Pin 4 | Black |
Load Cell → NAU7802¶
Connect the 4-wire load cell to the screw terminals on the NAU7802 board.
Load Cell (5kg) SparkFun Qwiic Scale
┌─────────────────┐ ┌─────────────────┐
│ Red ───────────┼────────────┤► E+ (Red) │
│ Black ─────────┼────────────┤► E- (Black) │
│ White ─────────┼────────────┤► A- (White) │
│ Green ─────────┼────────────┤► A+ (Green) │
└─────────────────┘ └─────────────────┘
| Load Cell Wire | NAU7802 Terminal | Function |
|---|---|---|
| Red | E+ | Excitation + |
| Black | E- | Excitation - |
| White | A- | Signal - |
| Green | A+ | Signal + |
Wire Colors Vary
Wire colors vary by manufacturer. If readings are negative or erratic, try swapping A+ and A-.
PN5180 NFC → Raspberry Pi Pico (SPI)¶
The NFC reader connects to the Raspberry Pi Pico via SPI.
Pico Pinout Reference¶
Raspberry Pi Pico
┌───────────────────┐
GP0 ─┤ 1 40 ├─ VBUS
GP1 ─┤ 2 39 ├─ VSYS
GND ─┤ 3 38 ├─ GND
GP2 ─┤ 4 37 ├─ 3V3_EN
GP3 ─┤ 5 36 ├─ 3V3 (OUT)
GP4 ─┤ 6 35 ├─ ADC_VREF
GP5 ─┤ 7 34 ├─ GP28
GND ─┤ 8 33 ├─ GND
GP6 ─┤ 9 32 ├─ GP27
GP7 ─┤ 10 31 ├─ GP26
GP8 ─┤ 11 30 ├─ RUN
GP9 ─┤ 12 29 ├─ GP22
GND ─┤ 13 28 ├─ GND
GP10 ─┤ 14 27 ├─ GP21 ← RST (RESET)
GP11 ─┤ 15 26 ├─ GP20 ← BUSY
GP12 ─┤ 16 25 ├─ GP19 ← SCK
GP13 ─┤ 17 24 ├─ GP18 ← MOSI
GND ─┤ 18 23 ├─ GND
GP14 ─┤ 19 22 ├─ GP17 ← NSS (CS)
GP15 ─┤ 20 21 ├─ GP16 ← MISO
└───────────────────┘
PN5180 Connections¶
| PN5180 Pin | Pico GPIO | Pico Pin # | Wire Color |
|---|---|---|---|
| VCC | 3V3 | 36 | Red |
| GND | GND | 33 or 38 | Black |
| SCK | GP19 | 25 | Yellow |
| MISO | GP16 | 21 | Orange |
| MOSI | GP18 | 24 | Green |
| NSS (CS) | GP17 | 22 | Blue |
| BUSY | GP20 | 26 | Pink |
| RST | GP21 | 27 | Brown |
3.3V Only!
The PN5180 is 3.3V only. Do NOT connect to 5V (VBUS) - it will damage the chip!
Quick Reference Card¶
┌────────────────────────────────────────────────────────────┐
│ SPOOLBUDDY QUICK WIRING REFERENCE │
├────────────────────────────────────────────────────────────┤
│ │
│ NAU7802 (Scale) → CrowPanel UART1-OUT │
│ ───────────────────────────────────── │
│ SDA → Pin 1 (IO19) VCC → Pin 3 (3V3) │
│ SCL → Pin 2 (IO20) GND → Pin 4 (GND) │
│ │
│ Load Cell → NAU7802 Terminals │
│ ───────────────────────────── │
│ Red → E+ Black → E- White → A- Green → A+ │
│ │
│ PN5180 (NFC) → Raspberry Pi Pico │
│ ──────────────────────────────── │
│ MISO → GP16 (Pin 21) SCK → GP19 (Pin 25) │
│ MOSI → GP18 (Pin 24) NSS → GP17 (Pin 22) │
│ BUSY → GP20 (Pin 26) RST → GP21 (Pin 27) │
│ │
│ PN5180 (NFC) → CrowPanel UART1-OUT │
│ ──────────────────────────────── │
│ VCC → Pin 3 (3V3) GND → Pin 4 (GND) │
│ 5V → Pin3 (3V3) (not redundant, enables antenna) │
│ │
│ Raspberry Pi Pico → CrowPanel UART1-OUT │
│ ──────────────────────────────── │
│ VSYS (Pin 39) → Pin3 (3V3) GP4 → Pin 1 (IO19) │
│ GND (Pin 38) → Pin4 (GND) GP5 → Pin 2 (IO20) │
│ │
│ Power │
│ ───── │
│ CrowPanel: USB-C 5V/2A │
│ │
│ Pico: powered from I2C │
│ (powering via USB is possible for debug purposes, │
│ but connection to VSYS (Pin 39) should be swapped to │
│ 3V3_EN (Pin37) when using it to prevent the USB-5V │
│ from seeping into the system) │
└────────────────────────────────────────────────────────────┘
Power Requirements¶
| Component | Voltage | Current (typical) |
|---|---|---|
| CrowPanel 7.0" | 5V (USB-C) | 300-600mA |
| Raspberry Pi Pico | 5V (USB) or 3.3V | 25-100mA |
| PN5180 | 3.3V | 80-150mA |
| NAU7802 | 3.3V | 1-2mA |
Recommendation
Use quality USB-C cables and a 5V/2A power adapter for the CrowPanel.
Wiring Checklist¶
NAU7802 → CrowPanel¶
- SDA → UART1-OUT Pin 1 (IO19)
- SCL → UART1-OUT Pin 2 (IO20)
- VCC → UART1-OUT Pin 3 (3V3)
- GND → UART1-OUT Pin 4 (GND)
Load Cell → NAU7802¶
- Red wire → E+ terminal
- Black wire → E- terminal
- White wire → A- terminal
- Green wire → A+ terminal
PN5180 → Pico¶
- SCK → GP19 (Pin 25)
- MISO → GP16 (Pin 21)
- MOSI → GP18 (Pin 24)
- NSS → GP17 (Pin 22)
- BUSY → GP20 (Pin 26)
- RST → GP21 (Pin 27)
PN5180 → CrowPanel¶
- VCC → UART1-OUT Pin 3 (3V3)
- 5V → UART1-OUT Pin 3 (3V3)
- GND → UART1-OUT Pin 4 (GND)
Pico → CrowPanel¶
- VSYS (Pin 39) → UART1-OUT Pin 3 (3V3)
- GND (Pin 38) → UART1-OUT Pin 4 (GND)
USB-powered Pico
If you wish to connect the Pico to USB-power (e.g. for debugging purposes), connect UART-OUT Pin3 (3V3) to 3V3_EN (Pin37) to prevent 5V power to seep into the 3.3V power distribution.