LoRa

I've started experimenting with another wireless data technology known as LoRa. LoRa ( Long Range ) is suitable for small amounts of data over distances up to several kilometres, and uses license free frequency bands in the UHF spectrum.

Regarding the hardware, my favourite development modules nowadays are based on the ESP32 microcontroller, ( see 02.8.20 ), and my searches discovered such modules with not only the built-in WiFi and Bluetooth capability of the ESP32, but also having LoRa transceiver chips as well ! I bought two, ( identical and with built-in OLED displays ), including antennas; one to be the transmitter, the other the receiver. Cost was just $23.

ESP32 based LoRa modules (R) transmitter (L) receiver

I uploaded some basic firmware I had written to program the modules for a simple test. I set up a very short 15cm link ( see image above, click to zoom ). The transmitter sends a data packet every few seconds comprising a text string "LoRa_868MHz" plus the packet number. The receiver displays the text in the received packet, the number of data bytes received and the received signal strength, RSSI, currently -45dBm.

Having got a LoRa link up and running the next step will be to connect a sensor to a remote transmitter, e.g., a soil moisture sensor outside in the garden, and send the sensor measurement to a receiver in the house. The herb patch in the far corner of my property would be a good choice of location. Because of the distance neither Bluetooth nor WiFi would be suitable technologies, and I'm guessing there's no WiFi coverage there anyway. 

A global LoRa network exists called LoRa-WAN, having an ever-increasing number of gateways giving access to it. My nearest gateway, 6.5Kms away, might receive my LoRa signal. Or I could setup my own gateway. Gateways are connected to Servers. So I could then log in to a server and see my sensor data when away from home. More information can be found at https://www.thethingsnetwork.org.

 

  

My first Android app

I've created my first Android app. It's called "SpacerLabs UV" and is for use with the WiFi version of my UV Radiation Meter, ( see post 12.01.2021 ). The UV Index can be read from the meter's web-server, without the complete web-page, and there is also no need to open a browser first. All this has been achieved using a cloud-based tool for developing applications for Android devices, called "MIT App Inventor", ( appinventor.mit.edu ), and without any programming knowledge needed !

Basically, developing an app is a two part process using the Designer view and then the Blocks view. First, design the display by positioning components, ( e.g., buttons, labels, text boxes etc ) onto a viewer that looks like a phone. Then, using the Blocks view, connect functional blocks to assign functions to the components e.g., what should happen when a button is tapped. If the "MIT AI2 Companion" app has been installed on a smart phone, the effect of changes can be seen on an actual phone in near real-time via WiFi. When the app is finished, it is saved as a .apk file which can be emailed to a recipient as an attachment from where it can be downloaded and installed on an Android device.

Tapping 'Get UV Index' updates the value

My choice of icon for the app

The lower image shows the icon I chose to launch the app. The top image shows the app opened on a smart phone. It looks quite primitive, having only a few components and no menu bar. But it serves its purpose well. The UV Index 6.54 was measured one sunny morning this month on my balcony.