A proof of concept to demostrate any measure captured from a accelerometer attached to a raspberry pi 3 and transport this information throw mqtt protocol to a hub server thats centralize this information using a mqtt message broker like mosca and message router like node-red to parse and manage. In this case we will use a node-red flow on the raspberry 3 and not python service to capture the accelerometer measures.
The Node-RED flow Designer in raspberry pi:
The Node-RED flow Designer in server side:
The Raspberry pi 3 and accelerometer connected
Architecture
- Raspberry pi 3: The Raspberry Pi is a series of credit card-sized single-board computers developed in the United Kingdom by the Raspberry Pi Foundation.
- MPU6050: The MPU-6050™ parts are the world’s first MotionTracking devices designed for the low power, low cost, and high-performance requirements of smartphones, tablets and wearable sensors.
- Raspbian: Last raspbian for raspberry pi. Raspbian is the Foundation’s official supported operating system.
- NodeJS: Event-driven I/O server-side JavaScript environment based on V8. Includes API documentation, change-log, examples and announcements.
- mosca: MQTT broker as a module http://mosca.io.
- Node-Red: A visual tool for wiring the Internet of Things.
- node-red-contrib-gpio: A set of node-red nodes for connecting to johnny-five IO Plugins.
- raspi-io: An IO plugin for Johnny-Five that provides support for the Raspberry Pi.
- node-red-contrib-graphs: A Node-RED graphing package.
Install GPIO Node-red packages on raspberry-pi 3 device:
-
Stop node-red if is still running
node-red-stop -
Start a root user from pi user:
sudo su - -
Modifiy the start user of the node-red service and set root
sudo nano /lib/systemd/system/nodered.service -
Start node-red, this will create a .node-red appplication directory to configure the new node red instance from root account
node-red-start node-red-stop -
Install in this last directory the new node packages to access the raspberry pi GPIO from nodejs
cd .node-red npm install node-red-contrib-gpio npm install raspi-io -
Exit the root account and restart node-red. Now the node-red instance start from root account, so the application directory of the node-red will be /roo/.node-red where we had installed all GPIO packages. This new nodes will used in our future flows to manage this pins of the raspberry pi.
exit node-red-start -
Access Node-Red raspberry pi Web designer
http://192.168.1.45:1880
- Copy and import this flow from node-red import clipboard to crete the raspberry pi flow
[{"id":"e0dd9e02.d117f","type":"mqtt-broker","z":"5e77b74b.936dc8","broker":"192.168.1.29","port":"1883","clientid":"","usetls":false,"verifyservercert":true,"compatmode":true,"keepalive":"60","cleansession":true,"willTopic":"","willQos":"0","willRetain":null,"willPayload":"","birthTopic":"","birthQos":"0","birthRetain":null,"birthPayload":""},{"id":"19d415f0.73ba1a","type":"nodebot","name":"","username":"","password":"","boardType":"raspi-io","serialportName":"","connectionType":"local","mqttServer":"","pubTopic":"","subTopic":"","tcpHost":"","tcpPort":"","sparkId":"","sparkToken":"","beanId":"","impId":""},{"id":"635ce998.acf998","type":"gpio out","z":"5e77b74b.936dc8","name":"","state":"I2C_READ_REQUEST","pin":"","i2cDelay":"0","i2cAddress":"104","i2cRegister":"59","outputs":1,"board":"19d415f0.73ba1a","x":209,"y":187,"wires":[["186bfa84.8252f5"]]},{"id":"3562881e.bf6c38","type":"debug","z":"5e77b74b.936dc8","name":"","active":true,"console":"false","complete":"false","x":534,"y":38,"wires":[]},{"id":"186bfa84.8252f5","type":"function","z":"5e77b74b.936dc8","name":"process i2c","func":"var data = msg.payload;\nvar int16 = function(high, low) {\n var result = (high << 8) | low;\n // if highest bit is on, it is negative\n return result >> 15 ? ((result ^ 0xFFFF) + 1) * -1 : result;\n};\n\n\nmsg.payload = {\n accelerometer : {\n x: int16(data[0], data[1]),\n y: int16(data[2], data[3]),\n z: int16(data[4], data[5])\n },\n temperature : int16(data[6], data[7]),\n gyro : {\n x: int16(data[8], data[9]),\n y: int16(data[10], data[11]),\n z: int16(data[12], data[13])\n }\n};\n\nreturn msg;","outputs":1,"x":334,"y":99,"wires":[["3562881e.bf6c38","f5563d59.de0aa"]]},{"id":"3086d0ad.426e8","type":"inject","z":"5e77b74b.936dc8","name":"","topic":"","payload":"14","payloadType":"string","repeat":"","crontab":"","once":false,"x":107,"y":97,"wires":[["635ce998.acf998"]]},{"id":"24705baf.328ae4","type":"gpio out","z":"5e77b74b.936dc8","name":"","state":"I2C_WRITE_REQUEST","pin":"","i2cDelay":"0","i2cAddress":"104","i2cRegister":"","outputs":0,"board":"19d415f0.73ba1a","x":493,"y":354,"wires":[]},{"id":"6997c4ec.8c13bc","type":"inject","z":"5e77b74b.936dc8","name":"","topic":"","payload":"","payloadType":"none","repeat":"","crontab":"","once":false,"x":143,"y":354,"wires":[["4c294d92.b11134"]]},{"id":"4c294d92.b11134","type":"function","z":"5e77b74b.936dc8","name":"i2c bytes","func":"msg.payload = [0x6B, 0x00];\nreturn msg;","outputs":1,"x":321,"y":354,"wires":[["24705baf.328ae4"]]},{"id":"f5563d59.de0aa","type":"mqtt out","z":"5e77b74b.936dc8","name":"","topic":"mpu6050","qos":"","retain":"","broker":"e0dd9e02.d117f","x":526,"y":129,"wires":[]}]
Install mosca mqtt message broker on the server side:
npm install mosca bunyan -g
mosca -v | bunyan
Execute npm to install node-red message router and the UI modules on the server, the package.json has all dependencies:
npm install
Start node-red
node node_modules/node-red/red.js
Access Node-Red server Web designer
http://localhost:1880/
- Copy and import this flow from node-red import clipboard to crete the raspberry pi flow
[{"id":"d4a328fc.110fd8","type":"mqtt in","z":"19f847a6.9b1408","name":"","topic":"mpu6050","qos":"2","broker":"e8b9681b.ed6e18","x":123,"y":102,"wires":[["9bfd210a.90696"]]},{"id":"9bfd210a.90696","type":"debug","z":"19f847a6.9b1408","name":"","active":true,"console":"false","complete":"false","x":367,"y":102,"wires":[]},{"id":"e8b9681b.ed6e18","type":"mqtt-broker","z":"19f847a6.9b1408","broker":"localhost","port":"1883","tls":null,"clientid":"","usetls":false,"compatmode":true,"keepalive":"60","cleansession":true,"willTopic":"","willQos":"0","willRetain":null,"willPayload":"","birthTopic":"","birthQos":"0","birthRetain":null,"birthPayload":""}]
The source code is released under Apache 2.0.