RFID readers and cards

The reader recognises the cards. You can choose between a reader that plugs into USB (simple) and readers that you wire to the pins of the Pi (cheap, a bit of work). Set the reader up with:

lauschctl setup rfid

The step asks which reader you have, enables the right plugin and installs what it needs. Connect all USB readers before you run it. The settings land in settings/rfid.yaml; you may run the step again at any time (it rewrites the file after asking). Restart Lauschkiste afterwards.

Choosing cards

Readers work at one of two frequencies: 125 kHz (RDM6300) or 13.56 MHz (all others). Cards, stickers and key fobs must match. With the MFRC522 only the types Mifare Classic 1k/4k and Mifare Ultralight work, not NTAG2xx.

Which readers notice a card staying on

Some readers send one signal when a card is put on. Others send a signal as long as the card is there; they allow music that stops when the card is taken off (Cards). Known to do this: RDM6300, MFRC522 (SPI) and PN532 (I2C). USB readers mostly do not.

The readers

Reader	Connection	Card stays on	Tested
USB readers	USB	mostly not	not yet
RC522 / MFRC522	SPI	yes	yes, in daily use
MFRC522 on I2C	I2C		not yet
PN532	I2C	yes	not yet
RDM6300	serial	yes	not yet
USB NFC readers without keyboard mode	USB		not yet

“Not yet” means: written and tested with automated tests, but not yet on real hardware by the project. Please report what you find.

USB readers (keyboard type)

Most cheap USB readers behave like a keyboard that types the card number. They need no wiring. The user running Lauschkiste must be in the group input (normally the case; otherwise sudo usermod -a -G input <user>).

RC522 / MFRC522 (SPI)

The cheap blue board. It talks over SPI, which the Raspberry Pi device plugin switches on (lauschctl setup raspi, then restart).

MFRC522	Function	Raspberry Pi	Pin
SDA	chip select	GPIO8 (SPI0 CE0)	24
SCK	clock	GPIO11 (SPI0 SCLK)	23
MOSI	data out	GPIO10 (SPI0 MOSI)	19
MISO	data in	GPIO9 (SPI0 MISO)	21
IRQ	interrupt	GPIO24	18
RST	reset	GPIO25	22
GND	ground		20
3.3V	power		17

Some boards label MOSI and MISO the other way round. Nothing breaks if you swap them wrong: if no card is read, swap the two wires. Without the IRQ wire the box polls, which uses a lot of CPU; without the RST wire the reset pin must be connected to 3.3V.

Options in rfid.yaml (config:): spi_ce (0 or 1), pin_irq (24), pin_rst (25), antenna_gain (4), mode_legacy (false; only for large collections of 4-byte numbers from older installations).

MFRC522 on I2C

The same chip over I2C, for example the M5Stack RFID 2 unit. Options: i2c_bus (1), i2c_address (0x28). To find the address install i2c-tools and run i2cdetect -y 1.

MFRC522	Raspberry Pi	Pin
5V	5V	4
GND	GND	6
SDA	GPIO2 (SDA)	3
SCL	GPIO3 (SCL)	5

PN532 on I2C

Good reading range and many card types, e.g. the Adafruit PN532 breakout. It needs two pins, but polls. Set its two jumpers for I2C: SEL0 on, SEL1 off. Connect 5V (not also 3.3V).

PN532	Raspberry Pi	Pin
5V	5V	4
GND	GND	6
SDA	GPIO2 (SDA)	3
SCL	GPIO3 (SCL)	5

RDM6300 (serial)

A 125 kHz reader on the serial port (UART). Its RX/TX levels are 3.3 V, not 5 V as often said; check your board before you wire anything. You wire pins at your own risk.

USB NFC readers without keyboard mode (nfcpy)

For USB NFC devices that cannot be used as a keyboard. nfcpy lists the supported devices. Connect the device before running lauschctl setup rfid: the step stops the kernel from claiming it and finds the device. To use several devices, give each its device_path in rfid.yaml, for example usb:072f:2200 (vendor and product ID).

rfid:
  readers:
    read_00:
      module: rc522_spi
      config: {}                 # reader specific, filled by lauschctl setup rfid
      same_id_delay: 1.0         # seconds before the same card counts again (against bouncing)
      place_not_swipe:
        enabled: false           # true: the card stays on; needs a reader that can tell
        card_removal_action:
          action: player.pause

card_removal_action is the same for all cards on that reader. Individual cards can switch the removal action off or the delay off, see Cards.