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Troubleshooting

Common problems and how to fix them.

Scale

Scale shows 0 or doesn't respond
  • Does the LED on the NAU7802 light up? If not, check power — 5V on Pin 1, GND on Pin 2 of the WT32 I/O connector
  • Check load cell wiring (E+/E-/A+/A-)
  • If values are negative, swap A+ and A-
  • Recalibrate via Settings → Scale → Calibration
Scale weight is inaccurate
  • Recalibrate with a precise reference weight (~1000 g recommended)
  • Make sure nothing touches the weighing platform during tare
  • Avoid vibrations during measurement
Scale reads correctly but Spoolman diff is wrong
  • Check if the spool weight is set correctly in Spoolman
  • Update bag weight via Settings → Scale → Bag Weight

NFC

NFC reader not detected on boot
  • Does the LED on the PN532 light up? If not, check power — 5V on Pin 1 of the WT32 I/O connector
  • Check PN532 jumpers — must be set to I²C mode
  • Verify wiring: SDA → Pin 3, SCL → Pin 4, RST → Pin 7
  • Do not connect PN532 via NAU7802 STEMMA QT passthrough (only 3.3V)
NFC tag not recognized
  • Hold the spool steady directly over the NFC window
  • Try a different NTAG sticker — some cheap stickers have defects
  • Not sure if your tag is compatible? See the NFC Tag Compatibility Guide

WiFi & Network

Device doesn't connect to WiFi
  • SpoolmanScale supports 2.4 GHz only — 5 GHz networks will not appear
  • Double-check password (case sensitive)
  • Move closer to the router during setup
Can't reach Spoolman from SpoolmanScale
  • Make sure Spoolman is running and reachable from another device on your network
  • Use the IP address, not a hostname
  • Check port — default is 7912
  • Verify both devices are on the same network

Firmware

Device doesn't appear in Web Flasher
  • Use a data-capable USB-C cable (many cables are charge-only)
  • Try a different USB port or computer
  • Use Chrome or Edge — Firefox does not support WebSerial
OTA update fails
  • Check WiFi connection
  • Try again — the GitHub download can time out on slow connections
  • Fall back to the Web Flasher or manual file upload if OTA keeps failing
Display shows nothing after flashing
  • Re-flash via the Web Flasher

SpoolmanScale Pro (Pi)

Can't reach spoolmanscale.local
  • On Windows: install Bonjour Print Services
  • Use the Pi's IP address directly as an alternative
  • Check that the Pi is powered and connected to WiFi
Backend doesn't start after reboot
  • Check systemd service: sudo systemctl status spoolmanscale-backend
  • Check Docker: docker ps
  • Check logs: docker logs spoolmanscale-ui

Still stuck?

Join the Discord — the community is happy to help.