[ITP: Understanding Networks] MQTT Client

I feel like I’m a week behind in this class because I’ve had 1 credit weekend classes over the last two weekends. Admittedly, I also ordered my sensor a bit too late, so I’ll try to send a few more days worth of data collection over Thanksgiving when I’m home in AZ.

What is MQTT?

MQTT is the standard for IoT messaging. It is designed as an extremely lightweight publish/subscribe transport that is ideal for connecting remote devices with a small code footprint and minimal network bandwidth. (https://mqtt.org/)

Get RGB Color Sensor Working with Arduino

I wanted to harness my inner Tom Igoe, so I ordered the TCS34725 RGB Sensor from Adafruit. I soldered on the included headers so that I could attach it to my bread board and connected it to my Arduino Nano 33 IoT using some jumper wires. In the Arduino IDE, I installed the Adafruit TCS34725 Arduino library and uploaded the “tcs34725.ino” example sketch.

Send Sensor Data over MQTT

Now that I’ve got my sensor working consistently, I can try to connect to the network. I started with the “MqttClientSender.ino” example. To be sure I’m sending my data to the correct place, I made the broker “test.mosquitto.org”, the topic “undnet/makin-stuff”, and the client “makinClient”.

To get my sensor data to send, I made sure to include the Adafruit library, create an instance of the Adafruit_TCS34725 object, and call it’s begin() function in setup(). In loop() I use the library functions to get lux and color temperature data from the sensor. I had to format the data in JSON to send over the MQTT client.

One cool tip I stole from Suraj is using the built in LED of the Arduino to indicate whether I’m still connected to the broker or not. Thanks Suraj!

Now that things are working I can check that it’s logging data using MQTT Explorer. Haha, there I am!

I let the sketch run for some time and periodically checked in on the debug statements. After about an hour or so I saw these error messages in the IDE and my built in LED turned off indicating that I lost connection to the broker.

I was also unable to connect to my land lady’s network at home. I figured I would try again when I got to my parents house for fall break and I wasn’t able to connect to their network as well which was super concerning. I tried out the “ScanNetworks” sketch from the WiFiNINA library and saw that the signal strength of my parents network was very poor (~-80dBm). I had glued down my antenna too good! I carefully removed some hot glue with a razor blade and more networks became available to my Arduino. It seems really straightforward, but it was also really satisfying to see the signal strength go up as I brought my Arduino closer to the router. Fingers crossed, I think removing the glue fixed my connectivity issues!

Setting up my Microservice

So I’m starting with Tom’s “MqttNodeClientFileWriter” example. I edited the client.js to fit my MQTT client by updating the “clientId” and “myTopic” variables to match my Arduino sketch. I also made sure the broker was the same, test.mosquitto.org. I also copied the package.json, package-lock.json, and an empty data.txt file to my folder because I figured it would be important. I pushed all this to github so that I could pull on my Digital Ocean host.

I cloned my repo on my Digital Ocean host, but I guess the linux terminal does not like spaces in names! Had to put an underscore in “Understanding_Networks” part of my repository’s name.

I made a copy of the folder on the home directory and installed dependencies with “npm install package.json”.

When I run the script in its directory with “node client.js” my Arduino seems to disconnect from the broker. It reconnects when I quit running my script. Super weird!

For now, I’m putting this exploration on pause. I thought it would be interesting to access the MQTT sensor data myself and do something with it. It’s not required for the assignment, so I’ll revisit this once I complete all the other assignments!