Parts list
This is everything you need to build one station. The firmware supports exactly one controller board and one NFC reader module, with fixed pins, so buy these parts and not look-alikes.
What to buy
| Part | Qty | Exactly what | Check before buying |
|---|---|---|---|
| Controller with touchscreen | 1 | WT32-SC01 Plus (ESP32-S3, 16 MB flash, 480 × 320 touchscreen) | It must be the Plus. The older WT32-SC01 (without "Plus") is a different board and does not work. |
| Scale converter | 1 | NAU7802 breakout board | See Choosing a NAU7802 board below. |
| Load cell | 1 | YZC-133, 5 kg (default) or 2 kg | A four-wire bar-type cell. Get the seller's wiring sheet and mounting drawing. Use one cell, not two. |
| NFC reader | 1 | ELECHOUSE NFC_ST25R3916B module (ST25R3916B chip, antenna on the board) | The module must be switched to I2C mode with its solder bridge (see Wiring). The pin order in this manual is for this module only. |
| NFC tags | one per spool | NXP ICODE SLIX2 (NFC-V / ISO 15693), blank | NTAG and MIFARE tags are found but not read. Other ISO 15693 tags are read but cannot be written. See Which tags work. |
| USB cable | 1 | A data cable that fits the board's USB socket | Charge-only cables cannot install the firmware. |
| 5 V power supply | 1 | A regulated 5 V USB supply | See Power. |
| Cable for the expansion connector | 1 | An 8-wire cable that fits the board's EXT connector | Match the connector on your board. |
| Cable for the NFC module | 1 | A 7-wire cable that fits the module's connector | Match the connector on your module. |
| Hook-up wire, pin headers | as needed | For the NAU7802 board and the load cell | Depends on your breakout board. |
| Enclosure | 1 | The printed case (three parts, about 299 g of filament), or a base and platform you build | The case needs 2 × M5 nuts, 2 × M5 × 12 button-head screws, 2 × M5 × 16 cap screws, 2 × M2.5 × 10 screws with nuts, four 12 mm rubber feet, a USB-C panel-mount cable and a right-angle USB-C plug. See Scale platform and enclosure. |
Choosing a NAU7802 board
- It has labelled VIN, GND, SDA and SCL pins.
- It has four load-cell terminals: E+, E−, A+, A−.
- Its documentation says which supply voltage it accepts.
- Its SDA and SCL lines work at 3.3 V. See Power.
You also need two tools for setup: a multimeter to check the cables before first power, and an object of known weight (no heavier than the load cell's capacity) to calibrate the scale.
What the project does not recommend
The project has not tested or measured any of these, so it names none:
- Sellers and prices.
- A specific NAU7802 board. Any breakout that meets the checks above should work.
- A current rating for the power supply.
For the curious: how the parts fit the firmware
You do not need this to buy or build. It shows what the firmware expects from each part.
| Part | What the firmware expects |
|---|---|
| WT32-SC01 Plus | ST7796 display and FT6336 touch, both built into the board. The expansion connector carries the scale and the NFC reader. |
| NAU7802 | Address 0x2A. The station sets it to gain 128, 3.0 V internal regulator, 10 readings per second. |
| YZC-133 | Capacity 5000 g or 2000 g. You choose 5 kg or 2 kg in the browser under Settings → Scale → Edit Load-cell profile → YZC-133 variant. The default is 5 kg. Changing it deletes the scale calibration. |
| NFC_ST25R3916B | Address 0x50, I2C mode, with the interrupt (IRQ) wire connected. |
| ICODE SLIX2 tag | 80 blocks of 4 bytes, tag ID starting E0:04. |
Reference documents
These come from the manufacturers, not from this project. The connector pin numbers in Wiring follow the first one.
- WT32-SC01 Plus datasheet (PDF)
- ELECHOUSE guide to I2C mode — use it for the solder bridge only. The GPIO numbers in its examples are for a generic ESP32 and do not apply to the station.