This tutorial explains the steps to make an inexpensive LoRa gateway and how I managed to run it. Then I show a complete scenario with nodes, gateways and cloud all together. Finally I will explore the possibility to manufacture a cheaper one.
With this tutorial anybody can make a complete LoRa gateway with about 200€ in parts. This project is not intended for a design and manufacture of a commercial gateway in big quantities.
A LoRa gateway runs around SX1301. This chip is not for sale in single unit quantities, and sell to qualified customers only. The only way is to buy an already made gateway board.
We are going to use a Multitech mCard-LoRa, about 156€:
Connected through a mPCIe to USB converter to a Raspberry Pi (25€).
The RF chain, highlighted in blue, has a balun, SAW filter, PA, filter and switch in the TX path and a SAW filter, LNA and SAW filter in the RX path. In the other layer there is a FTDI SPI to USB converter and some LDOs. Looking at power pins of the card, GND pins are routed to ground and 3.3v power pins (2, 24, 52) are routed the input of some voltage regulators (the ones used for digital domain supply). But regulators inputs for analog domain are routed to pins 23 and 25. This doesn’t meet the Mini-PCIe specification because that pins are assigned to the Express lane. The three LP38502SD-ADJ LDOs used for the analog part are adjusted to 3.3v output, then LDOs need a supply greather than 3.52v as the dropout is 220mV. In short, I decided to supply pins 23 and 25 of the Mini-PCIe connector with 5v from the USB connector. I have done this fix in the adapter bought: this completes all the hw modifications needed.
Software download and modifications are available on the official GitHub project page.