Input I²C or SPI selection. Pull low for SPI, high for I²C

Configurable:
SPI clock input
Determines LSB of I2C address - tie to GND to clear LSB, tie to 3V3 to set LSB

Configurable:
Serial comms data enable to drive EIA485 transceiver
SPI chip select. Pull low to select.
Determines LSB‑1 of I2C address - tie to GND to clear LSB‑1, tie to 3V3 to set LSB‑1

Configurable:
Serial comms transmit (3V3 logic)
I²C data input / output. (Pull up resistors must be fitted on host board)
SPI data output

Configurable:
Serial comms receive (3V3 logic)
I²C clock input. (Pull up resistors must be fitted on host board)
SPI data input

USB 5V - note this does not power the module, only for data enable

USB data

USB data

3V3 logic drive for external buzzer - variable frequency, 50/50 mark/space

Pull low to bypass config.txt on startup

Serial LED 3V3 logic output - ‘Neopixel’ protocol. Host must provide 5V driver

Connect to antenna via matching circuit

Connect to antenna via matching circuit

Driven high when a payload is available to be read and can be used to wake up the host processor

Reserved for future use. Recommended to connect this pin to host GPIO so the functionality could be used when released.

Flag signal for data availability on the host connected serial interface (I²C/SPI)

Power to module. 3.3V to 5V

Serial comms transmit

Serial comms receive

Pull low to reset module