Design

The board uses a Raspberry Pi Pico, this has the advantages of being inexpensive, readily available and easy to flash. The LoRa module I have chosen is the AiThinker Ra-01SH which uses the newer Semtech SX1262 LoRa chip. This gives us a similar hardware package to the Waveshare SX1262 LoRa Module for Pi Pico for which the official firmware was designed. The pin connections on this board have been designed to mimic those of the Waveshare hat, minimising any requirement to alter the firmware.

Two boards have been produced for this project. The first is the base board which features an edge mount SMA male connector.

Second is the portable version of this board featuring a PCB antenna. Until such time as this has been properly range tested and Bluetooth functionality is developed this remains experimental and I would advise caution in using it for anything besides test purposes.

The PCBs can be ordered very reasonably from JLCPCB using the Gerbers available in the downloads section.

The board options are entirely up to you however I would recommend a board thickness of 1.6mm in order to accommodate the SMA edge connector and I would always recommend using tented vias whenever surface mounting one PCB onto another. This will mean there is a layer of solder screen over the vias which reduces the risk of shorts from any exposed metal on the attached module's underside.

The BOM (the stuff you're going to need and what it's going to cost)

JLCPCB have a minimum order quantity of 5 so for this example the prices are based on buying enough parts to make this many nodes.

AliExpress prices change with the wind so everything stated is correct as of the time of writing and includes delivery. Hopefully you'll have at least some of this stuff lying around in a drawer somewhere or know someone else who does.

Each node is going to require the following:

1 x Custom PCB - JLCPCB - £0.70

1 x Raspberry Pi Pico - AliExpress - £2.30

1 x AiThinker Ra-01SH SX1262 LoRa Module - AliExpress - £4.13

1 x 0805 10uF Capacitor (C1) - AliExpress - £0.01 (pack of 100)

1 X 0805 100nF Capacitor (C2) - AliExpress - £0.01 (pack of 100)

1 x 0805 200k Resistor (R1) - AliExpress - £0.01 (pack of 100)

1 x 0805 100k Resistor (R2) - AliExpress - £0.01 (pack of 100)

1 x Edge Mount SMA Female Connector - AliExpress - £0.55 (pack of 10)

Total cost Per Board - £7.72