Troubleshooting¶

Problems the scale cannot work out by itself: network, backend, tags, the Pi.

Check the status bar first

Anything wrong with the hardware, the scale diagnoses itself and says so in plain words. Every message it can show, with cause and fix, is under What the scale is telling you.

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 shows an absurd number, e.g. -3487423847234 g

That number is not a measurement. When the I²C bus is broken, every register read comes back as all ones, which the firmware reads as "conversion ready" plus a sample of -1. Fix the bus first, the number follows.

Open the serial monitor at 115200 baud and look at the boot line I2C_EXT scan: - it lists every address that answers. Expected: 0x24 PN532, 0x2A NAU7802
Repeated [E][Wire.cpp:499] ... returned Error -1 means "no device acknowledged". That is a wiring fault, not an address conflict: 0x24 and 0x2A cannot collide, and the touch controller sits on a separate bus
Check the solder joints while the plug is seated. A cold joint measures fine on the bench and opens under strain
SDA (Pin 3) and SCL (Pin 4) not swapped, GND (Pin 2) continuous

Weight is still wrong after fixing the wiring

A calibration taken while the bus was broken is stored in the device and survives the repair.

Settings → Scale → Reset calibration, then TARE and calibrate again with a reference weight

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 (PN532 RSTPDN) → Pin 7, see Wiring
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
Too close is more common than too far: 5 to 20 mm between tag and reader work best, see Positioning
Not sure if your tag is compatible? See the NFC tags

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)
Password contains ^, ~, | or `? Firmware before v0.7.2 cannot type them. Flash the current version with the web flasher, which then also asks for the WiFi
Hidden network: it does not appear in the list. Use Set up by phone and type its name, see Step 2 - WiFi
Move closer to the router during setup

Can't reach the backend from the scale

Make sure the backend is running and reachable from another device on your network
Use the IP address, not a hostname
Check the port - the usual ones are Spoolman 7912, FilaMan 8083, BamBuddy 8000. Without a port the request goes to port 80
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

Web Flasher says: Failed to initialize

The flasher found the port but cannot reach the chip. Try these in order:

Close everything that may hold the USB port: Arduino IDE, a slicer, a second tab with the flasher.
Use a different cable, one that carries data, in a USB port straight on the computer, no hub.
Put the scale into download mode by hand. The display board has only a RST button on its back. BOOT (GPIO0) is on the 7-pin DEBUG connector next to it, and the optional debug board (ZXACC-ESPDB) plugged in there has both buttons.

With the debug board: hold BOOT, press and release RST, release BOOT.

Without it: bridge pin 6 (BOOT) and pin 7 (GND) of the DEBUG connector with a short wire, press RST, remove the wire. Pin 1 at the other end carries 5V, so find GND with a multimeter first: it beeps against the metal shell of the USB-C socket.

The screen stays dark, that is right: the chip now waits for the flasher. Connect in the flasher and install, then press RST once.

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

Update is not offered, or “no longer fits”

0.8.0 divides the scale's memory anew, and that only works over the cable. A scale still on the old layout says the update no longer fits, or the web upload reports that the file is larger than the storage of this scale. The firmware on the device is fine, only the memory layout is too small.

Update once over USB: open the web flasher in Chrome or Edge, connect the scale and choose Update. It takes about 2 minutes, and all settings are kept
If the flasher offers "Install" instead, leave "Erase" unticked, or WiFi and calibration are gone
After that, updates arrive over the air as before. Details on Updating the firmware

Display shows nothing after flashing

Re-flash via the Web Flasher

Sending a log / bug report

Open the Logs page in the web interface. It needs the Maintenance switch
Set Scope to Verbose, then repeat what went wrong
No SD card? Set Write the log to Internal. The internal storage holds 4,096 lines, that is several hours at Verbose
Download the log and post it on Discord or in a GitHub issue, with the firmware version and the backend you use

SpoolmanScale Pro (Pi)¶

Can't reach spoolmanscale-pro.local

On Windows: install Bonjour Print Services
Use the Pi's IP address from your router instead
The Pi finds no network at all? After 90 seconds it opens its own setup WLAN, see Set up the Pi

A backend does not start

Log on its tile on the Overview shows what the backend says
The service's own log: journalctl -u spoolmanscale-pro -n 100
Its data broken? Restore a backup on the Backup tab

Forgot the login of the Pi

On the Pi: sudo rm /var/lib/spoolmanscale-pro/auth.json, reload the page and create the login again

Still stuck?

Join the Discord - the community is happy to help.