maziggy
e9200449ae
Reproduced live during the #1133 rollout: the SpoolBuddy display kept serving the pre-fix picker for hours after every cache-clear, chromium-restart, and pkill attempt because a chain of stale state across HTTP cache + Service Worker + persistent profile prevented fresh code from reaching the running tab. Three independent changes — any one of them sufficient on a clean profile, but all three needed to escape an already-corrupted one: (1) backend/app/main.py — index.html now served with Cache-Control: no-cache, must-revalidate on both / and the SPA catch-all. Vite emits content-hashed JS/CSS bundle filenames so the assets themselves are safe to cache forever, but the HTML wrapping them is the only file that knows which hash is current. Without explicit cache directives Chromium falls back to heuristic caching (typically 10% of time since Last-Modified) and on long-running kiosks happily serves stale HTML across browser restarts. That stale HTML references an old bundle hash which is also still in disk cache, so the kiosk runs pre-deploy JS forever without ever knowing why. (2) frontend/public/sw.js — CACHE_NAME bumped from bambuddy-v25 to bambuddy-v26 so any client that fetches the new sw.js drops its old CacheStorage. The SW does network-first for HTML/JS/CSS but intercepts and falls back to cache, and cache-control on HTTP responses doesn't reach into the SW's own cache layer. (3) spoolbuddy/install/install.sh — generated kiosk launcher now uses --user-data-dir=/tmp/spoolbuddy-kiosk-userdata with a pre-launch rm -rf, so every kiosk restart starts from a clean slate (no HTTP cache, no SW registration, no IndexedDB). Trade-off is a slightly slower first paint and zero offline support; neither matters for a single-purpose kiosk facing a backend on the same LAN, and the guarantee that next-deploy-just-works is worth far more. 4 new tests in test_static_html_cache_headers.py: index.html on / and SPA catch-all paths emit Cache-Control: no-cache, must-revalidate; API routes are unaffected (no leak of HTML cache directive onto endpoints we want React Query to cache aggressively). For existing kiosks already trapped by an old persistent profile, operator runs once: rm -rf ~/.config/chromium && systemctl restart getty@tty1.service. The new launcher then picks up automatically.
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). Manual CS via GPIO23 with
spidev.no_cs = Trueresolves this.
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.