How to send matrices to ThingSpeak?

Greetings! My project is to read in data from two arduinos and then separate the data into four matrices. These matrices are comprised of 8 values and are sent to ThingSpeak when filled (to 8). My issue is that I am attempting to send 4 matrices to ThingSpeak via this line :

thingSpeakWrite('ChID',{heartRateInputA,temperatureInputA,heartRateInputB,temperatureInputB},'WriteKey','myWriteKey');

When I execute this, the data goes through but only the first column of the 1-D array. How do I send the whole array? Attached below is the rest of my code.

    %Uses two sets of nested 'if' loops and variables and ThingSpeak channels
%to read in and parse data from each controller

a = Bluetooth('HC-05',1);
b = Bluetooth('IN',1);

a.ReadAsyncMode = 'continuous';
b.ReadAsyncMode = 'continuous';

fopen(a); %data collector A
fopen(b); %data collector B

%A data points
heartRateVarA=0;
temperatureVarA=0;

%B data points
heartRateVarB=0;
temperatureVarB=0;

col = 1; %column counter for matrices

heartRateInputA = [];
temperatureInputA = [];

heartRateInputB = [];
temperatureInputB = [];

while (a.Status == 'open')&(b.Status=='open')
%if data has been sent to thingSpeak, reset the column counter
    if(col == 15)
       col=0; 
    end
col = col+1;    

for i=1 : 1 : 2
 matchA = fgets(a);    
 matchB = fgets(b);

 testA = contains(matchA,'Celsius');
 testB = contains(matchB,'Celsius'); 

%Test A parsing 

 if (testA==1)
     temperatureVarA=matchA;
 else
     testA=contains(matchA,'BPM');
     if(testA==1)
         heartRateVarA=matchA; 
     end
 end

 %Test B parsing

if (testB==1)
   temperatureVarB=matchB;
else
   testB=contains(matchB,'BPM');
   if(testB==1)
       heartRateVarB=matchB;
   end
end

end

%Display read and parsed in data

    fprintf('Device 1 : \n\n');disp(col);
    fprintf('Heart Rate A : '); disp(heartRateVarA);
    fprintf('Temperature A : '); disp(temperatureVarA);

    fprintf('Device 2 : \n\n');
    fprintf('Heart Rate B : '); disp(heartRateVarB);
    fprintf('Temperature B : '); disp(temperatureVarB);

    %Removes non-numeric characters from data and sends to respective
    %matrix
    hInputA = str2double(strrep(heartRateVarA,'BPM: ',''));
    tInputA = str2double(strrep(temperatureVarA,'Celsius: ',''));
    hInputB = str2double(strrep(heartRateVarA,'BPM: ',''));
    tInputB = str2double(strrep(temperatureVarB,'Celsius: ',''));

    heartRateInputA(1,col) = hInputA;
    temperatureInputA(1,col) = tInputA;
    heartRateInputB(1,col) = hInputB;
    temperatureInputB(1,col) = tInputB;

    %create arbitrary time stamps of same size as data points to send data to
    %thingspeak
    stamps = [datetime('now')-minutes(length(matchA)-1):minutes(1):datetime('now')]';

    pause(2); %pauses for 2 seconds to coincide with arduinos

    if(col==8)
        col=1;

        thingSpeakWrite(501358,{heartRateInputA,temperatureInputA,heartRateInputB,temperatureInputB},'WriteKey','JLS6DXUINWFGI6QD');

    end
end

Thanks in advanced.

Answer 1

[James Holland]

I was unable to find a way to send an entire matrix into a single ThingSpeak field but found a different method. Refer to my last comment for the method I used.

https://www.mathworks.com/matlabcentral/answers/410613-how-to-send-matrices-to-thingspeak#comment_590228

Answer 2

[Image Analyst]

You're sending in a cell array since you have braces around your arrays, but since you say it's not working, maybe try converting it to a table variable and sending that in instead.

[James Holland]

Thank you, I tried this method but had to combine both heartRateInputA and temperatureInputA into one variable - device1 - and then use cell2table to create a table. When I tried to send this new, 2-by-8 table to field 1 of my ThingSpeak channel, it said :

Number of columns in 'Values' must be equal to the number of fields specified.

Any idea how to solve this?

[Image Analyst]

Not without seeing your cell2table command.

[James Holland]

Of course, here is what I attempted :

>> device(1,1:8) = heartRateInputA

device =

     0    69    71    56   129   144   113   109

>> device(2,1:8) = temperatureInputA

device =

           0          69          71          56         129         144         113         109
           0        2381        2405        2377        2377        2431        2394        2397

>> device1Table = cell2table(num2cell(device))

device1Table =

2×8 table

    Var1    Var2    Var3    Var4    Var5    Var6    Var7    Var8
    ____    ____    ____    ____    ____    ____    ____    ____

    0         69      71      56     129     144     113     109
    0       2381    2405    2377    2377    2431    2394    2397

>> thingSpeakWrite('channelID','Fields',1,'Values',device1Table,'WriteKey','myWriteKey');
Error using thingSpeakWrite
Number of columns in 'Values' must be equal to the number of fields specified.

[Image Analyst]

Well of course you need to actually put the actual numerical channel ID (501358) in there instead of the string 'channelID'. Did you do that?

[James Holland]

Yes I have the actual ID, write key, and such in the fields, just left it out for privacy.

[James Holland]

Currently, the data goes to ThingSpeak as long as I don't specify a field on the channel. This means that each element of the array is sent to an individual field. for example :

    heartRate = 0 69 56 77;

    thingSpeakWrite(channel,heartRate);
    thingSpeakRead(channel,'Field',1);
  ans = 0

    thingSpeakRead(channel,'Field',2);
  ans = 69

And so on so forth. How can I place all the data from a matrix into one field on the channel?

[Image Analyst]

I just got my devices and haven't yet set up my channel so you're a bit ahead of me. Maybe you can ask Hans Scharler at the Mathworks. That's who I've been talking to and he's very helpful.

[James Holland]

Thank you! Fortunately, it seems that I have found another method. Since MATLAB was able to send 8 data points to each channel, I just created a channel for each sensor. To display the data neatly, I created a MATLAB visualization to plot the pairs for their corresponding device as such:

hrB = thingSpeakRead(541121,'ReadKey','readKey'); %heart rate from device B
tempB = thingSpeakRead(541123,'ReadKey','readKey'); %temperature data from device B

%create line plot for deviceB
y3 = hrB;
y4 = (tempB/100);
x = (0.1:length(hrB));

thingSpeakPlotYY(x,y3,x,y4,'Color1','red','Color2','blue','YLabel1','Heart Rate','YLabel2','Temperature','Title','Device A');

The above was for Device B but Device A is almost the same.

[Héctor Cruz Guardo]

Hola James Holland, quisiera preguntarte un pequeño problema que manejo con una Tarjeta de Adquisicion de datos DAQ la cual de una entrada me entrega una matriz de salida, como hago para transferir dato por dato obtenido de la matriz a Thingspeak por medio de simulink, gracias