2 Feb 2019

LoRa - first steps

It took all of (maybe?) an hour to setup 2 Adafruit Feather M0 with RFM95 LoRa Radio devices and have them ping each other using the simple getting started guide and default Arduino code. Yes Arduino, boo hiss, I agree. But it was a very simple and easy way to perform a quick test which helps answer a few basic feasibility questions.

As some of you know, we own a farm, which presents lots of amazing opportunities for electronics projects: remote sensing, remote control, recording, etc. It would be great to know if someone cranks up the heat in the tack room, then leaves without turning it back down again. It would be great to know if someone accidentally leaves a light on, or a door open, somewhere in the barn. It would be great to be alerted if the electric fence goes down. It would be fantastic to be able to track water temperature in numerous places throughout our outdoor wood boiler HVAC system and correlate that with ambient room temperatures and outdoor temperature. It would be even more amazing to be able to track property-wide and area-specific electricity usage and water usage. And perhaps even consider some HVAC control projects too! Then there's motion sensing, detecting cars/people coming and going, gate operations/accessibility, wildlife/herd tracking, mailbox alerts, ..., it's quite a list!

But before I can even start to dream too much, I need to look at a lot of mundane things and figure out a whole bunch of details. For example: how do I communicate with things over the length (685m) and width (190m) of our property (~30acres)? What's the best way to communicate with things in the barn? Does everything need to be plugged in, or are batteries feasible?

One of the challenges that might not be readily obvious to most, is that the barn is mostly wrapped in metal. Trying to do wireless things in, around, through, and past an all-metal-wrapped barn is not straight-forward. Even our house has a metal roof. Another challenge is the fact our house is made of field-stone, and has roughly 17" thick concrete/stone walls! Try getting WiFi out of the underground basement through a 17" concrete/stone wall!

I'm sure to most people, it's obvious WiFi isn't a solution. Maybe sections of the property could be covered by WiFi, but it's certainly not the solution everywhere. And even at that, trying to cover an outdoor area in WiFi requires outdoor antennas, and WiFi extenders (which are not cheap, and can be difficult to get them to work together). Not to mention: WiFi is hard on battery-operated devices. Obviously Bluetooth isn't going to cut it either. So that eliminates all those Espressif ESP8266/ESP32 and BT/BTLE devices. A traditionally popular option would be Zigbee, but I get the feeling its popularity is waning. The rising star today for "IoT things" seems to be LoRa, so I wanted to give that a try. Ideally though, I'd like to try Zigbee too, so I can evaluate it and LoRa side-by-side.

But how well is LoRa going to work on my property? Sure we hear all sorts of amazing numbers describing the theoretical LoRa range, but these results always come with provisos. How well is LoRa going to work from my basement? Through my house's thick walls? Past the all-metal barn? Over the hills? And through the forest?

Then on top of LoRa itself is this whole LoRaWAN stuff and The Things Network... (whatever those things are).

Above the radio we then have to consider microcontrollers. I wouldn't want to wake up one day to find that I had grown overly-biased in my preference for one microcontroller over all others. But having worked with 8-bit PICs, 8-bit AVRs, and 8051s, I have to say: those 32-bit CortexMs from ARM are pretty sweet! Maybe I'll consider using a PIC here or there just to improve my microprocessor breadth, but they won't be a top priority. Another up-and-coming microcontroller that I'll want to experiment with would be one of those smaller RISC-V designs such as the FE310.

On top of the microcontroller goes the code. As I said above, the Arduino environment is cute for some quick prototyping, but ideally I'd prefer to be closer to the hardware. Popular choices in the maker community include MicroPython and Adafruit's CircuitPython. Those are okay choices and both have their place, but only you're fond of "single control-loop" designs. Through these projects I'm hoping to explore MicroPython, CircuitPython, and, yes, even Arduino stuff, but ultimately I'd like to spend most of my time with things like FreeRTOS, Zephyr, mbed, and libopencm3. Any others I should consider?

Above the "firmware" comes higher-level software such as messaging. I'm guessing MQTT is the only sensible choice here?

I'm still not done. Another item that needs serious attention are all the various hardware choices: hardware form-factors, batteries, weatherproof enclosures, .... If every item is going to be a one-off design, then I can try a bunch of different boards, batteries, enclosures, and form-factors to see which ones work better than others. But if I want to build up an ecosystem of devices all built on the same known platform, then I need to consider standardizing on some of these options.

I like what Adafruit has done with their Feather line of development boards. They're standardized, breadboard-able, have LiPo connectors and charging hardware onboard, and have an ever-growing ecosystem of daughter-boards (FeatherWings). What's nice about the Feather ecosystem is how the user has a choice of microcontroller for the baseboard itself. I think it would be fair to call Adafruit's Feather ecosystem a form-factor for The Internet of Things. Are there any others worth considering?

I started out saying how it didn't take very long to get two of these boards sending messages to each other. Although my research had told me that it should work easily, I was still very amazed when I took one of the boards, plugged in a LiPo battery, put everything inside a weatherproof enclosure, brought it to the barn, and returned to my desk to find they were still communicating! The barn is about 80m (~260') away, and my office is underground, behind a 17" thick concrete/stone wall! I tweaked the code a little, but didn't make any changes to the radio operation other than to set the frequency. I'm using just a plain, simple 3" wire soldered to the "antenna" pad. Wow!

And with this little experiment, I've (finally!) started down the path of (hopefully!) many fun, electronics, farm projects! I now know I can at least communicate from my desk to the barn over LoRa using a simple 3" wire antenna and two tiny Feather boards.

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