SensorTag to Blynk Using Node-RED

Node-RED provides an elegant solution to merge different IoT devices and services. 

• The SensorTag acquires weather data and sends them to the Raspberry Pi through BLE (Bluetooth Low Energy).

• The Node-RED flow runs on the Raspberry Pi, processes the weather data and sends to the Blynk server, either on the cloud or locally, through WiFi.

• An iOS- or Android-based phone or tablet connects to the same Blynk server, either on the cloud or locally, and displays the measures on a beautiful way.

The RedBear IoT pHAT provides BLE and WiFi to the Raspberry Pi Zero.

​General Preparation

​Download the Debian Jessie Lite image and prepare a microSD-card.

​On macOS, I’m using ApplePi-Baker to prepare the microSD-card. 

​In order to enjoy SSH through USB, update the microSD-card on the main computer with
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• ​At the very bottom, add 
• Press ctrl-O ctrl-X to save and close.

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• Then launch 

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• ​​After rootwait, add a space.
  

• Press ctrl-O ctrl-X to save and close.

• Power-cycle the Raspberry Pi.

• ​Connect to the Raspberry Pi, with an USB cable on USB port. On the main computer. 

Default password is raspberry.

​To proceed with the update and upgrade,

• Launch on the Raspberry Pi

Code Editor

To set the timezone,

• Launch on the Raspberry Pi 

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• ​Install and run rpi-update.
  
• Launch on the Raspberry Pi ​​

Install RedBear IoT pHAT

• ​Power the Raspberry Pi off,
  
• Plug the RedBear IoT pHAT on the Raspberry Pi,
  
• Power the Raspberry Pi on,
  
• Connect to it and launch

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If the answer is IoT pHAT w/eep_v0.3, the board is ready. Proceed to next section. Otherwise, the EEPROM needs to be updated. Just follow this procedure.
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​To confiture WiFi,

• Launch on the Raspberry Pi​

• Add at the end
• Press ctrl-O ctrl-X to save and close. ​

• ​​Finally, reboot.

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• ​Connect using Ethernet over USB or WiFi.
  
• Launch on the main computer

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Default password is raspberry.

​To check Bluetooth is running,

• Launch on the Raspberry Pi

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​To scan Bluetooth devices,

• Launch on the Raspberry Pi

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The SensorTag Node-RED requires Bluetooth, as well as an Ethernet over USB connection or a WiFi connection

​Install node, npm and Node-RED

• ​Launch on the Raspberry Pi

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• ​Check

• ​To obtain release 0.12 of node, launch on the Raspberry Pi

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• ​To install Node-RED

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• ​To install npm to manage additional nodes,

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• ​To obtain release 2.15 of npm, launch on the Raspberry Pi

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​Install Additional Nodes

​There are two releases for the SensorTag, node-red-contrib-sensortag and node-red-node-sensortag. I managed to get the first one to work.

• Install the node.

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• ​List the installed nodes

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• ​To install the Blynk node, launch on the Raspberry Pi Zero

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​Launch the Blynk App

On the iOS- or Android-based phone or tablet,

• Install the Blynk app and launch it.
  

• Enter your credentials, either to the Blynk cloud or to a local server.
• Create a new project.
• Press E-mail to have the auth token sent.

For each measure, add a widget.

• Select one widget among the long list,
  
• Name it, and
  
• Define a virtual pin.

​On the right, temperature is defined on virtual pin V0, and light on virtual pin V3.

​Develop the Node-RED Flow

• ​Launch Node-RED with one of the two commands.

• Connect using Ethernet over USB or WiFi
  

• Open http://raspberrypi.local:1880 on a browser. 
  

Click to enlarge.


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• Click-and-drop the SensorTag from the left pane to the main area.
  

• Each time the Deploy button on the top-right turns red, click Deploy to launch the flow.
• ​On the SensorTag node, click on Scan and select your SensorTag.

• Select the sensors from the SensorTag to be included in the messages.

​If connection doesn't work,

• Launch bluetoothctl in a separate connection and disconnect the SensorTag with

​On the SensorTag node,

• Press Rescan and select the line with B0:B4:48:ED:B4:84, corresponding to your SensorTag. 

• Add a Debug node and connect it to the SensorTag node.

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​The SensorTag outputs
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• ​On the Node-RED GUI, add a function node and define it with

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• Do the same for other messages.
  
• Replace the msg.sensor criteria and the payload:msg.payload.json_data.field accordingly.

For example, the criteria for light is "luxometer" and the field payload:msg.payload.json_data.lux. 

​On the Node-RED GUI,

• Add a Blynk write node and define the URL and project key.
  

​The project key is the auth token sent from the Blynk app.

The URL could be

• the Blynk cloud, or

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• the IP address of a local server.

The finalised flow looks like

• Click Deploy.

• Press Update and define the virtual pin. 
• Do the same for the other measures, with different numbers for the virtual pins.

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• Move the SensorTag and check the measures change accordingly on the phone or the tablet.