Seeed Studio Studio Wio-LR1121 Wireless LoRa Module w/ IPEX

The Wio-LR1121 communicates with a host MCU via an SPI interface. You must connect the module's SPI pins (MOSI, MISO, SCK, CS) and a reset pin to your microcontroller. Initialization involves pulling the reset pin low, then high, before sending configuration AT commands or LoRaMAC-node library commands over SPI to set the frequency band, spreading factor, and output power. Ensure your firmware handles the specific SPI timing requirements of the LR1121 chip.

Band switching is managed through the LR1121's internal RF switch, controlled via specific SPI register writes. Your firmware must send a command sequence to deactivate the current radio, reconfigure the RF front-end parameters (center frequency, bandwidth) for the new band, and then re-enable the radio. The integrated TCXO maintains stability during the switch. Reference the Semtech LR1121 datasheet and Seeed Studio's example code for the exact register values for 868MHz, 915MHz, or 2.4GHz ISM operation.

Use a 50-ohm antenna with an IPEX4 (1.5mm) plug matched to your target frequency band. For sub-GHz (868/915MHz), a λ/4 whip or PCB antenna with ~3dBi gain is typical. For 2.4GHz, a smaller chip or dipole antenna is used. Antenna gain directly impacts the link budget; a 3dBi gain antenna can effectively add 3dB to both transmit and receive performance. Ensure the antenna is impedance-matched to 50 ohms to prevent VSWR issues that reduce efficiency and range. Keep the RF trace short on your PCB.

To achieve the specified 1.35µA sleep current, you must correctly use the module's deep sleep mode. After communication, send the SPI command to put the LR1121 into its lowest power sleep state. Crucially, your host MCU must also tri-state (set to high-impedance) its SPI lines connected to the module. Any GPIO pins held high or low by the MCU can create a current leakage path. Power the entire node from a low-quiescent-current LDO regulator. Measure sleep current with a multimeter in series with the battery.