Wiring¶

All components connect to the I/O connector on the WT32-SC01 Plus using the included 7-pin cable. The I/O socket has 8 pins — plug the 7-pin cable in flush to the left.

The PN532 and NAU7802 share the same I²C bus (SDA/SCL) and are wired in parallel.

Do not daisy-chain via NAU7802 STEMMA QT passthrough

The NAU7802's STEMMA QT passthrough port only supplies 3.3V. The PN532 requires 5V. Always connect both modules directly to the WT32 I/O connector.

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WT32-SC01 Plus I/O Connector¶

Pin	Color	Signal	Connects to
1	Red	5V	PN532 VCC + NAU7802 VIN
2	Black	GND	PN532 GND + NAU7802 GND
3	Yellow	GPIO10 (SDA)	PN532 SDA + NAU7802 SDA
4	Green	GPIO11 (SCL)	PN532 SCL + NAU7802 SCL
5	Blue	—	unused
6	White	—	unused
7	Brown	GPIO12 (RST)	PN532 RST

ASCII — I/O Connector Overview¶

  WT32-SC01 Plus I/O Connector (8-pin, use pins 1-7)
  ┌───┬───┬───┬───┬───┬───┬───┬───┐
  │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │
  │5V │GND│SDA│SCL│ - │ - │RST│   │
  └───┴───┴───┴───┴───┴───┴───┴───┘
    │   │   │   │           │
    │   │   │   │           └── PN532 RST
    │   │   └───┴── PN532 SDA + NAU7802 SDA (parallel)
    │   │       └── PN532 SCL + NAU7802 SCL (parallel)
    │   └────────── PN532 GND + NAU7802 GND
    └────────────── PN532 VCC + NAU7802 VIN

PN532 NFC Reader¶

The PN532 has no connector — wires must be soldered directly.

Solder from the back

Always solder from the back of the PCB — there is not enough clearance on the front once it's mounted in the enclosure.

Recommended Assembly Order¶

Solder all other components first (NAU7802, load cell, WT32 breakout cable)
Leave the PN532 wires loose and long enough to work with
Feed the wires up through the PN532 mount opening from below
Solder to the back of the PN532 PCB
Slide the PN532 into its mount and route cables into the enclosure

JST SH 1.0mm connector

If you use a 5-pin JST SH 1.0mm pigtail on the PN532, the mount opening is just large enough to pass the connector through — allowing you to solder everything outside the enclosure and plug in during final assembly.

PN532 Pinout (JST SH 1.0mm 5-pin, 3rd party cable colors)¶

PN532 Pin	Color (3rd party)	Signal	WT32 I/O Pin
1	Black	GND	Pin 2 (Black)
2	Red	5V	Pin 1 (Red)
3	Yellow	SDA	Pin 3 (Yellow)
4	White	SCL	Pin 4 (Green)
5	Orange	RST	Pin 7 (Brown)

ASCII — PN532 to WT32¶

  PN532                            WT32-SC01 Plus I/O
  ┌──────────┐                     ┌──────────────────────┐
  │          │                     │                      │
  │  GND  ───┼── Black ─────────── │── Pin 2  (GND)       │
  │  VCC  ───┼── Red ───────────── │── Pin 1  (5V)        │
  │  SDA  ───┼── Yellow ────────── │── Pin 3  (GPIO10)    │
  │  SCL  ───┼── White ─────────── │── Pin 4  (GPIO11)    │
  │  RST  ───┼── Orange ────────── │── Pin 7  (GPIO12)    │
  └──────────┘                     └──────────────────────┘

NAU7802 Scale ADC¶

The safest option is soldering directly to the labeled pads on the NAU7802 (VIN, GND, SDA, SCL). Alternatively, use the STEMMA QT connector — but note that 3rd-party JST SH 1.0mm cables have a different pin order and require re-pinning.

NAU7802 Pinout (STEMMA QT, JST SH 1.0mm 4-pin)¶

STEMMA QT Pin	Color (3rd party)	Signal	WT32 I/O Pin
1	Black	GND	Pin 2 (Black)
2	Red	5V	Pin 1 (Red)
3	Yellow	SDA	Pin 3 (Yellow)
4	White	SCL	Pin 4 (Green)

ASCII — NAU7802 to WT32¶

  NAU7802                          WT32-SC01 Plus I/O
  ┌───────────────────┐            ┌──────────────────────┐
  │                   │            │                      │
  │  GND  ────────────┼── Black ── │── Pin 2  (GND)       │
  │  VIN  ────────────┼── Red ──── │── Pin 1  (5V)        │
  │  SDA  ────────────┼── Yellow ──│── Pin 3  (GPIO10)    │
  │  SCL  ────────────┼── White ── │── Pin 4  (GPIO11)    │
  └───────────────────┘            └──────────────────────┘

Load Cell¶

Load Cell wire	NAU7802 terminal	Function
Red	E+	Excitation +
Black	E-	Excitation -
White	A+	Signal +
Green	A-	Signal -

Negative scale values?

If the scale shows negative values, swap A+ and A-.

ASCII — Load Cell to NAU7802¶

  Load Cell                       NAU7802
  ┌──────────────┐                ┌───────────────────┐
  │              │                │  Screw Terminals  │
  │  RED    ─────┼── Red ──────── │── E+              │
  │  BLACK  ─────┼── Black ─────  │── E-              │
  │  WHITE  ─────┼── White ─────  │── A+              │
  │  GREEN  ─────┼── Green ─────  │── A-              │
  └──────────────┘                └───────────────────┘

Full System Overview¶

  WT32-SC01 Plus I/O (Pins 1-7)
  ┌─────────────────────────────────────────┐
  │ Pin 1 (5V)   ───────┬─────────────────── PN532 VCC
  │                     └─────────────────── NAU7802 VIN
  │ Pin 2 (GND)  ───────┬─────────────────── PN532 GND
  │                     └─────────────────── NAU7802 GND
  │ Pin 3 (SDA)  ───────┬─────────────────── PN532 SDA
  │                     └─────────────────── NAU7802 SDA
  │ Pin 4 (SCL)  ───────┬─────────────────── PN532 SCL
  │                     └─────────────────── NAU7802 SCL
  │ Pin 7 (RST)  ─────────────────────────── PN532 RST
  └─────────────────────────────────────────┘

                                NAU7802 Screw Terminals
                                ┌──────────────────────┐
                                │ E+ ── Load Cell RED   │
                                │ E- ── Load Cell BLACK │
                                │ A+ ── Load Cell WHITE │
                                │ A- ── Load Cell GREEN │
                                └──────────────────────┘

Wiring Photos:¶

Step 1 Step 2 Step 3 Step 4

Next Step¶

➡️ Assembly