c1123365da
Reporter on a Raspberry Pi 5 couldn't read NFC tags — gauge worked, SPI bus and wiring fine, but PN5180 transfers didn't complete. Manually commenting out `self._spi.no_cs = True` restored communication. Root cause: Pi 5's RP1 southbridge SPI driver (spi-rp1) doesn't honour the SPI_NO_CS ioctl the way the historical Broadcom driver on Pi 4 did. Safe to relax Pi-wide. SpoolBuddy's PN5180 NSS line is wired to GPIO23 (manual CS in _cs_low / _cs_high — the kernel's default auto-CS timing doesn't meet the PN5180's 5µs setup / 100µs hold spec). The hardware CE0 line (GPIO8) is not connected to the reader, so whether the kernel auto-toggles it is electrically invisible. The no_cs = True call was always cosmetic on this hardware. Wraps the assignment in try/except OSError in both the daemon and the diagnostic script; the daemon logs at debug level so future Pi-5-specific triage is greppable. README updated to drop the "spidev.no_cs = True resolves this" sentence and explain the manual GPIO23 CS scheme carries the timing on its own.
5.4 KiB
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.