Dual LoRa module adapter for BeagleBone

This PCBA connects widely available LoRa modules based on Semtech SX127x RFIC, such as this module (archive) sold on Aliexpress for less than $3, to the Texas Instruments BeagleBone family of single board computers.

Requirements

The module must have a size of 16 by 16 mm, and have 16 castellated pads with 2 mm spacing; for details, see the Kicad footprint. The module pinout must match the following, viewed from the top:

Pin 1?
ANT		GND
GND		DIO5
DIO3		nRESET
DIO4		nCS
3V3		SCK
DIO0		MOSI
DIO1		MISO
DIO2		GND

These modules do not have a clearly marked pin 1, so the actual pinout may be rotated 180° compared to the above.

See also the bill of materials.

Usage

BeagleBone pinout

The following table lists the BeagleBone pins and their connections:

Radio#	Function	BB pin	CPU pin
radio0	nRESET	P9_15	gpio1[16]
radio0	IRQ	P9_16	gpio1[19]
radio0	nCS	P9_17	gpio0[5]
radio0	SCK	P9_22	gpio0[2]
radio0	MOSI	P9_18	gpio0[4]
radio0	MISO	P9_21	gpio0[3]
radio1	nRESET	P9_25	gpio3[21]
radio1	IRQ	P9_27	gpio3[19]
radio1	nCS	P9_28	gpio3[17]
radio1	SCK	P9_31	gpio3[14]
radio1	MOSI	P9_30	gpio3[16]
radio1	MISO	P9_29	gpio3[15]

Radio 0 is connected to CS0 of SPI0, radio 1 is connected to CS0 of SPI1.

BeagleBone pin mux configuration

To configure BeagleBone pins, run the following commands:

sudo modprobe spidev
sudo chown $USER /dev/spidev*

config-pin P9_15 gpio_pu
config-pin P9_16 gpio_pu
config-pin P9_17 spi_cs
config-pin P9_22 spi_sclk
config-pin P9_18 spi
config-pin P9_21 spi

config-pin P9_25 gpio_pu
config-pin P9_27 gpio_pu
config-pin P9_28 spi_cs
config-pin P9_31 spi_sclk
config-pin P9_30 spi
config-pin P9_29 spi

These commands were tested on Debian 12 (bookworm).

Basic functional test

To perform a basic test of module functionality, install spi-tools and run the following commands:

echo '0: 4200' | xxd -r | spi-pipe -b 2 -d /dev/spidev0.0 | xxd
echo '0: 4200' | xxd -r | spi-pipe -b 2 -d /dev/spidev1.0 | xxd

Both commands should return the following output:

00000000: 0012                                     ..

The number 12 is the module ASIC revision.

Full functional test

Steps for performing a full test of module functionality, including radio transmission and reception, will be provided later.

Revision history

A1 : Initial revision

Terms of distribution

The adapter is covered by the CERN-OHL-P (permissive) license. See LICENSE.txt for details.