accelerometer data from Raspberry to Thingspeak not displaying properly

Hello

I am hoping someone can help please. I have connected my raspberry pi 3 to a Thingspeak channel and set up two fields to be read and displayed, 'Temperature' and 'Accelerometer'. The temperator information is displayed as a field chart but the accelerometer is not. I know the raspberry pi is reading it as the values are printing and when I use 'export recent data' I can see the information there. Am I missing something in getting accelerometer information to display as a field? I am importing with 2 fields but I checked with another field (pressure) and it worked so I know the code for two fields is right.

Any help greatly appreciated.

Answer 1

[Vinod]

Are you sure your data in the field 2 is numeric? When you export the data, does it show as numeric or text?

If the data in the field is non-numeric, you will have to use MATLAB to parse the data and plot it.

Answer 2

[Claire McV]

Yes, it is numeric, here's a sample of the exported data: {"created_at":"2019-12-19T10:50:29Z","entry_id":376,"field2":"{'y': 0.06191210821270943, 'x': 0.020850349217653275, 'z': 0.9745436906814575}"},{"created_at":"2019-12-19T10:50:44Z","entry_id":377,"field2":"{'y': -0.0016885813092812896, 'x': 0.021820131689310074, 'z': 0.9686949253082275}"}]}

[Vinod]

Looks like the data sent to thingspeak is not numeric, but a JSON object.

"field2" is being set to (literally) "{'y': 0.06191210821270943, 'x': 0.020850349217653275, 'z': 0.9745436906814575}"

You can do one of two things:

1) Use MATLAB to unpack the XYZ values that are encoded as JSON, unpack the data and plot it

2) Modify the code on the device to send 'x', 'y' and 'z' values to 3 different fields on the channel and use built in plotting.

Answer 3

[Claire McV]

Thank you so much, and sorry for the confusion. I am a complete novice at this, which option would be the easiest and most straightforward, in your opinion? Any tips would be much appreciated.

Many thanks

Claire

[Vinod]

I'd say since you already have the data coming in, using MATLAB to extract the data would be the easiest way to do what you need. Check out the thingSpeakRead function and the jsondecode functions in MATLAB that you can use in your MATLAB visualization app on ThingSpeak.