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Nightly backups to a mounted NAS share ran from May and then stopped, failing with [Errno 30] Read-only file system. The reporter checked folder permissions -- correctly: the mount is gid=backup,dir_mode=0775, the service user is in that group, and his own shell writes to the share fine. Errno 30 is EROFS. A permission problem is errno 13. EROFS means the filesystem refused the write, and it refused because we told it to: our systemd unit ships ProtectSystem=strict, which mounts everything read-only inside the service's mount namespace and carves back out only ReadWritePaths=<install> <data> <logs>. A NAS share is not one of those three. Reads are unaffected -- which is why the UI happily listed his existing backups from the share while being unable to write a new one -- and his shell is outside the namespace entirely, so every check he could think to run said the directory was fine. Both installers write the unit file wholesale, so a ReadWritePaths line added by hand disappeared on the next install, taking the backups with it. They now back the old unit up (.bak-<timestamp>) and carry the operator's extra writable paths forward, reporting which ones they kept. The unit template documents the carve-out. The output directory is probed with a real write when it is saved and when the backup card loads, so an unwritable path is caught there rather than at 03:00 for a week. On failure the card names the cause and hands over the fix with the operator's path already in it (systemctl edit bambuddy -> ReadWritePaths=...), and a failed run reports the same diagnosis rather than the raw OSError. EROFS outside systemd, permission-denied, out-of-space, not-a-directory and missing are told apart, in all 11 locales. Docker: a backup path that is not bind-mounted is writable -- the write lands in the container's ephemeral layer and is lost on the next compose up. The probe compares the directory's device against the container root and warns, with the compose snippet that mounts it properly. |
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| daemon | ||
| install | ||
| scripts | ||
| tests | ||
| README.md | ||
SpoolBuddy Hardware Setup
PN5180 NFC Reader (SPI)
Wiring
| PN5180 Pin | Raspberry Pi Pin | GPIO | Wire Color |
|---|---|---|---|
| 3V3 | Pin 1 | — | Red |
| 5V | Pin 2 | — | Red |
| GND | Pin 20 | — | Black |
| SCK | Pin 23 | GPIO11 | Yellow |
| MISO | Pin 21 | GPIO9 | Blue |
| MOSI | Pin 19 | GPIO10 | Green |
| NSS (CS) | Pin 16 | GPIO23 | Orange |
| BUSY | Pin 22 | GPIO25 | White |
| RST | Pin 18 | GPIO24 | Brown |
Power: The PN5180 board has two power pins. 3V3 powers the IC itself, 5V powers the antenna booster and extends read range. Both should be connected. Do NOT connect 5V to the 3V3 pin — it will destroy the reader.
NSS: We use GPIO23 for manual chip-select instead of the default SPI CE0 (GPIO8) because the kernel SPI driver's automatic CS timing does not meet the PN5180's requirements (5µs setup, 100µs hold). The reader's NSS line is wired to GPIO23 only, so whether the kernel auto-toggles CE0 is electrically invisible to the PN5180. Pi 4 and Pi 5 are both supported — the code asks the driver to disable CE0 toggling but tolerates Pi 5's RP1 driver rejecting that request (#1424).
Setup Steps
1. Enable SPI and I2C
After a fresh Raspberry Pi OS install, SPI and I2C are disabled by default.
sudo raspi-config
# Navigate to: Interface Options -> SPI -> Enable
# Navigate to: Interface Options -> I2C -> Enable
sudo reboot
Verify after reboot:
ls /dev/spidev0.*
# Should show: /dev/spidev0.0 /dev/spidev0.1
ls /dev/i2c-*
# Should include: /dev/i2c-1
2. Configure /boot/firmware/config.txt
Add the following lines under the [all] section:
# SpoolBuddy: I2C bus 1 for NAU7802 scale (GPIO2/GPIO3)
dtparam=i2c_arm=on
# SpoolBuddy: Disable SPI auto CS (manual CS on GPIO23 for PN5180)
dtoverlay=spi0-0cs
i2c_arm=onenables I2C bus 1 (GPIO2/GPIO3). The NAU7802 is wired to bus 1. manual CS on GPIO23 because the driver's CS timing doesn't meet the PN5180's
Then reboot:
sudo reboot
Verify after reboot:
ls /dev/i2c-1
# Should exist
sudo i2cdetect -y 1
# Should show 0x2A (NAU7802)
3. Install system packages
sudo apt install python3-spidev python3-libgpiod gpiod libgpiod3 i2c-tools
python3-spidev/libgpiod3— system libraries for SPI and GPIO accessgpiod— command-line GPIO tools (useful for debugging)
pip install spidev gpiod smbus2
spidev— Python SPI bindings (PN5180 NFC reader)gpiod— Python GPIO bindings via libgpiod (works on both RPi 4 and RPi 5)
Wago connectors or breadboard jumpers are unreliable for SPI — the PN5180 is very sensitive to signal integrity issues (loose connections cause RF field flickering, phantom errors, and intermittent communication failures). Solder all wires directly for reliable operation.
6. Verify hardware communication
Run the diagnostic script to confirm the PN5180 is responding:
sudo python3 spoolbuddy/pn5180_diag.py
Expected output includes product version (e.g. v4.0), firmware version,
register dump, and "Diagnostics complete" at the end.
7. Test tag reading
sudo python3 spoolbuddy/read_tag.py
Place a tag on the reader. Supported tag types:
| Tag Type | SAK | Use Case |
|---|---|---|
| MIFARE Classic 1K | 0x08 |
Bambu Lab filament tags |
| MIFARE Classic 4K | 0x18 |
Bambu Lab filament tags |
| NTAG (213/215/216) | 0x00 / 0x04 |
SpoolEase / OpenPrintTag |
Troubleshooting
| Symptom | Cause | Fix |
|---|---|---|
| All zeros from SPI reads | SPI not enabled | Run raspi-config and enable SPI, then reboot |
GENERAL_ERROR on SEND_DATA |
Automatic CS timing too fast | Use manual CS on GPIO23 with spi0-0cs overlay |
BUSY timeout |
Wiring issue or RST not connected | Check RST and BUSY pin connections |
| RF field flickering on/off | Loose power wires | Solder all connections |
No tag found but tag is present |
Wrong protocol or missing setTransceiveMode() |
Ensure ISO 14443A config (0x00, 0x80) and setTransceiveMode() before every SEND_DATA |
| Auth failed for block N | Wrong key derivation | Verify HKDF uses context "RFID-A\0" (7 bytes including null terminator) |
EBUSY when requesting GPIO8 |
Kernel SPI driver owns CE0 | Use GPIO23 for NSS instead |
Technical Notes
- SPI speed: 500 kHz (higher speeds cause communication errors)
- SPI mode: 0 (CPOL=0, CPHA=0)
Wiring
| NAU7802 Pin | Raspberry Pi Pin | GPIO | Wire Color |
|---|---|---|---|
| VCC | Pin 1 | — | Red |
| SDA | Pin 3 | GPIO 2 | Yellow |
| SCL | Pin 5 | GPIO 3 | White |
| GND | Pin 30 | — | Black |
I2C Bus: Uses I2C bus 1 (GPIO2/GPIO3), enabled via
dtparam=i2c_arm=onin config.txt.
Verify
sudo i2cdetect -y 1
# Should show 0x2A
sudo python3 spoolbuddy/scale_diag.py
The diagnostic reads 10 samples at 10 SPS and shows raw ADC values, average, and spread. Typical idle readings are around ~500k with a spread under 20k.