Lorawan Recommendations

[Matthew Daubney]

Hello!

I'm looking to write an MQTT->LoRaWAN bridge so I can pop a GPS tracker on my bike and hook it to my home sensor network. So sensor->LoRaWAN->internet->mqtt->all my myriad of sensor programs.

Is there a preferred micro architecture for this? Can I get away with a cheap 8 bit micro or will I need to go ARM or somesuch? I can only find the one Microchip LoRaWAN device, are there any others (these seem to be £10+ each and in short-ish supply).

Thanks,

[mikethebee]

Good news is that TheThingsNetwork are supporting an mqtt service, it will replace the api fully soon. I recommend you sign up out TTN forum at https://groups.google.com/forum/#!forum/tvttnug where Andrew Lindsay and others more expert than me can answer the technical questions.

Richard I. and Ryan are working on a great little board with sensors on board, and a bluetooth to TTN bridge device for BT sensors. ThingInnovations.uk is Andrew's business and Thingitude.com is the company we have setup up to help support things like yours. The Microchip RN4283 is our preferred module, but it is on hold awaiting re-certification after some firmware changes.

Look at ttnreading.org for a list of resources. I'm always happy to help you, and I want to organise an rLab workshop on TTN and sensors, looking at early June when we should have some hardware available.

-Mike

[Richard Ibbotson]

Hi Matt,
I don't think you need a LoRaWAN bridge.
As Mike says, use the Things Network, which can probably do all the parts required to get data to your home sensor network. Using the Things network is the most sensible for a bike to give the roaming you need. If you need coverage where there is currently none, then add a gateway to the network and increase coverage for all.

At the device end, then you don't really need MQTT, you just need to send short data packets which can then be presented through MQTT from the Things network to your sensor network.

At the device end you need a LoRaWAN radio. Radios are based on the SX1276 or SX1272 chip from Semtech. The Semtech chip is a bare radio and you program its functions through lots of registers These can be used bare, or on a board module. The RN2483 from Microchip is one of these modules, it is a Semtech chip supported by a PIC. All the code for LoRaWAN is on the PIC and you can talk with a simple serial protocol, they cost around £8, but still have had some technical and supply problems. An advantage for commercial applications is that the LoRaWAN code  on the module has approval from LoRaWAN Alliance, but this can also limit functions of device and time to market.The HopeRF RFM95W is a module with just a SX1276 chip(actually a licensed copy) and the RF bits. This does not have a PIC, so you do all the LoRaWAN protocol in firmware using a stack written by IBM called LoRa MAC in C (LMIC). LMIC will run on an 8 bit Atmel, but is a bit tight due to the encryption code. Most LMIC implementations use  a small ARM processor. The RFM95W cost about £6 from China, there are other similar boards.

So to build a device you have many options.
You could link a GPS to an ATMega328 with an RN2483, or keep an eye on what Andrew at Things innovations is doing to get maybe a more ready built solution and add GPS to that.
Sodaq are doing a GPS + RN2483 product on a kickstarter:
https://www.kickstarter.com/projects/sodaq/loraone-the-lora-iot-development-board
We have a working prototype of our rThing One which is GPS + ARM Cortex M0 + 9 Axis, + Temp/humidity + RFM95W. It can be fitted with an OLED display or many I2C peripherals. Can show you that if you like. Ryan is reworking PCB due to couple of errors, plus we are adding a micro USB to make programming more simple for other people. It is the size of an 18650 battery and can be programmed direct from the Arduino environment.
The blue tooth prodcut is still not public, but can tell you about that too.
We are also looking to move away from SX1276 modules to bare chips to get the price down, same for GPS modules.