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Configure Transceiver GPIOs#
Using the Sidewalk protocol on the sub-GHz radio band with an EFR32 radio board requires the Semtech SX1262MB2CAS LoRa shield. The Semtech shield can be connected to the main board using either an adapter board (recommended) or 10 female-to-female jumper wires (if adapter board is not available). Using this third-party sub-GHz radio module enables sub-GHz communication from EFR32xG21 and EFR32xG24 radio boards. The Semtech shield is not necessary with the KG100S, as it already includes the Semtech chip.
Ⓘ INFO Ⓘ: For superior signal integrity, ease of use, and a more robust development platform, Silicon Labs recommends the Sidewalk Adaptation Board (BRD8042A, included in the Silicon Labs Pro Kit for Amazon Sidewalk) instead of jumpered wire connections.
When using the Sidewalk Adaptation Board, connect it to the main board Expansion Header as shown below, and mount the Semtech shield to the female pin headers on the Adaptation Board.
When using jumper wires, connect the Semtech shield to the main board Expansion Header with the following scheme:
EFR32 Mainboard Exp. Pin | Semtech Shield Pin | Function |
|---|---|---|
EXP_HEADER 1 | J3-6 | GND |
EXP_HEADER 4 | J2-4 | SPI MOSI |
EXP_HEADER 6 | J2-5 | SPI MISO |
EXP_HEADER 8 | J2-6 | SPI SCK |
EXP_HEADER 10 | J1-8 | SPI NSS |
EXP_HEADER 11 | J2-1 | ANT_SW |
EXP_HEADER 12 | J1-6 | DIO1 |
EXP_HEADER 13 | J1-4 | BUSY |
EXP_HEADER 14 | J4-1 | SX NRESET |
EXP_HEADER 2 | J3-4 | VMCU |
If you wish to customize the wiring between your sub-GHz chip and the EFR32, you can implement such changes in your application with the Pin Tool (in Simplicity Studio). When using the KG100S module, you also need to edit the GPIO mappings in file app_gpio_config.c in the sub-GHz example applications.
⚠ WARNING ⚠: In KG100S applications Silicon Labs recommends not using the SPI peripheral, because the multi-chip module (MCM) design already leverages it for communication between the EFR32 and the Semtech radio transceiver. Sharing the SPI bus with additional devices can negatively impact time-critical radio control signals and lead to message failure in sub-GHz protocols.