Wireless

Wireless connectivity for my home hobby devices is provided using the LoRa protocol implemented using dev boards that make use of Semtech devices. Check here for Semtech info and their LoRa overview. This page focuses on how to use the Semtech SX1280 device.

My network uses a star topology with a single access point implemented by connecting a Beaglebone to an SX1280 dev board. The network nodes are AVR MCUs connected to SX1280 dev boards. The SPI serial bus is used for both the Beaglebone and AVR interfaces.

Power Budget

Rx worst case cost:

(Sleep to STDBY_RC) = 1200 us @ 700 uA = 2.3e-7 mAh
(STDBY_RC to RX) = 85 us @ 700 uA = 1.652e-8 mAh
(Rx Time @ 325 kBit/sec) = 3.1 us/bit @ 7 mA = 6e-9 mAh/bit

Tx worst case cost:

(Sleep to STDBY_RC) = 1200 us @ 700 uA = 2.3e-7 mAh
(STDBY_RC to RX) = 85 us @ 700 uA = 1.652e-8 mAh
(Tx Time @ 325 kBit/sec) = 3.1 us/bit @ 18 mA = 1.54e-8 mAh/bit

Pinout

Relevant pins for my designs:

GND
VDD: 1.8V to 3.7V.
NSS_CTS (input): SPI slave select (active low).
MOSI_RX (input): SPI slave input.
MISO_TX (ouput): SPI slave output.
CLK_RTSN (input): SPI clock.
NRST (input): Active low reset signal.
BUSY (ouput): Transceiver busy indicator.

/lib

Wireless

Power Budget

Pinout

SPI Hello World