AdaFruit. IO nRF24L01 Windows 10 IoT Core Field Gateway

Part 1

For school Internet of Things(IoT) projects, I needed a robust field gateway for uploading telemetry data from a number of "cheap n cheerful" sensor nodes.

The distances involved were modest 5M (indoors) to 600M (outdoors) so a mix of Low & high power nRF24L01 wireless modules looked like a suitable choice.

After looking at several Cloud IoT Services AdaFruit.IO looked like it had sufficient flexibility and a reasonable pricing model. The security model (Feb 2018) with a shared API Key will have some challenges in wider scale deployments

Initially, I was going to use the Adafruit.IO MQTT interface but have found that getting an HTTP endpoint (fine for telemetry) white-listed in a school environment is easier.

While reading the AdaFruit.IO API documents I noticed that they have published a swagger definition of the API so I used NSwag to generate a C# client. I added a partial class with a single method to put an HTTP Header with the AdaFruit.IO API Key (see AdaFruit.IO.Swagger\APIKey.cs for details) on every request.

The field gateway hardware is Raspberry PI 2/3 based with an "off the shelf" shield (with some simple modifications).

The Field Gateway configuration is stored in a JSON file (a sample file is provided in the Github repo).

Edit [2018-03-10] application now generates an empty configuration file when first run so the one on GitHub is no longer required.

{
"AdaFruitIOUserName": "User Name here",  
"AdaFruitIOApiKey": "API Key here",  
"AdaFruitIOGroupName": "Group Name Here",  
"RF24Address": "Base1",  
"RF24Channel": 15,  
"RF24DataRate": "DR250Kbps",  
"RF24PowerLevel": "High",  
"RF24AutoAcknowledge": true,  
"RF24DynamicAcknowledge": false,  
"RF24DynamicPayload": true
}

Part 2

The UserName, APIKey & GroupName fields need to be updated then the file uploaded to the LocalState directory in application folder.

User Folders\LocalAppData\ AdaFruitIO.IoTCore.FieldGateway.NRF24L01-uwp_1.0.0.0_arm__nmn3tag1rpsaw\LocalState\

I use the device portal "Apps\File Explorer".

WARNING: Pay attention to the case of your settings.

https://io.adafruit.com/UserNameHere/feeds/GroupNameHere.5c-86-4a-00-c4-13h 

The Windows 10 IoT Core device logs useful information via Realtime ETW Tracing which can be viewed in the Device Portal Debug\ETW after enabling the "Microsoft-Windows-Diagnostics-LoggingChannel" provider.

Once the application is configured and tested you can use the Device Portal\Apps Manager to set the program to run on device startup.

Part 3

I have created several sample sensor nodes which use the same SeeedStudio Grove temperature and humidity sensor:

• Arduino/Seeeduino

• devduino V2.2

• Netduino

For an enclosure I use an off the shelf box from a local electrical supplies wholesaler.

The JSON configuration file has the following settings

• AdaFruitIOUserName - from "View AIO Key" on homepage of AdaFruit.IO portal

• AdaFruitIOApiKey - from "View AIO Key" on homepage of AdaFruit.IO portal

• AdaFruitIOGroupName - from the "Feeds" page of the AdaFruit.IO portal

• RF24Address - 3 to 5 characters long

• RF24Channel - 0 - 127

• RF24DataRate options

DR1Mbps
DR2Mbps
DR250Kbps

RF24PowerLevel options

Minimum
Low
High
Max

RF24AutoAcknowledge

True
False

RF24DynamicAcknowledge

True
False

RF24DynamicPayload

True
False

Adafruit have produced a series of videos about how to configure Adafruit.IO devices, feeds, groups and dashboards.