Help using ThingSpeak TimeControl Recurring

Hello:

Using the Timecontrol app, I want to execute a MatlabAnalysis recurring daily at 6:00 A.M. but execute it only ONCE. The MatlabAnalysis code performs a Thingspeakwrite() to a channel. I have the impression that the execution of this code is called multiple times during minute 00. I cannot write to a field more than every 30 seconds i believe. What can I do? Thanks in advance!

Below is my MatlabAnalysis code:

NHRS=6;
disp(['process the last ' num2str(NHRS) ' hours of pool level measurements']);  
channelID = xxxxxx; 
[data timestamps]= thingSpeakRead(channelID, 'NumPoints', 100, 'Fields', 5);
ts=timestamps;
indx=find(~isnan(data));
data1=data(indx);
ts1=ts(indx);
[N dummy]=size(data1);
[data2]=data1(N-NHRS+1:N);
ts2=ts1(N);
%disp('last 24 pool data levels');
%disp(data2);
disp(' ');
disp('time stamp of last pool level measurement');
disp(ts2);
% Calculate the average
avgValue = mean(data2);
% display the aveage
disp(['mean: ' num2str(avgValue) ' cm']);
% calcul the std deviation
sd=std(data2,1); 
%display the std deviation
disp(['sd: ' num2str(sd) ' cm']);
thingSpeakWrite(xxxxxx,[avgValue,sd],'WriteKey','xxxxxx');

[Christopher Stapels]

You should be able to complete your goal with this code and the appropriate timeControl.

What do you mean by "I have the impression that the execution of this code is called multiple times during minute 00" Your code seems fine at first glance, though im nto sure the use of the disp statements will help you when you run the timeControl, except for debug.

Answer 1

[William Glass]

below is my results and attached is my timecontrol config

process the last 6 hours of pool level measurements

time stamp of last pool level measurement

03-Nov-2026 18:09:49

mean: -9.99 cm

sd: 1.1801 cm

Error using Calculate and display average and sd of poolLvl (line 25)

Requests are too frequent. For further information, see Limitations in the documentation.

[William Glass]

See my message showing results in my other post. The channel is written to OK though but will it work the next days?

[dpb]

@William Glass, why did you make this an Accepted Answer instead of a Comment?

Anyway, that is an artifact I overlooked...

Is that log from a schedule execution or from a manual submittal to test the code? If it were scheduled at 6:20 PM, there's a 10 min difference so the 15-sec (free account) write update limit wouldn't have come into play.

However, if you're manually testing, then would have to be sure to not try to execute the code again inside that window -- and 15 sec is quite a long time if just sitting at the terminal.

The other thing to check is to look at the channel upload data -- use

https://thingspeak.com/channels/ID_NUMBER/feeds.json?api_key=YOUR_KEY&results=5

to see the actual time stamps of all uploaded data to make sure some other process isn't still running in the background and causing the conflict.

[dpb]

@William Glass - "The channel is written to OK though but will it work the next days?"

As noted, it's not clear from the post how the test was run -- see my follow-on above. If you try manually, if you have/are using a free account then you'll need to be sure you don't try a second time too soon. Otherwise, it's "wait a day and see". Unless there's something else going on we can't see, it appears it should work ok. As above, you can double-check for certain the update proceess is the only one actually writing and it isn't conflicting. The posted timestamps make it appear at superficially to not be an issue. What is the intended update frequency and who's doing the updating?

[William Glass]

Scheduled result for 6:15 pm. Manually, no errors if I don't run the code for > every 15 sec. If you see my config I'm not a sprcialist about sending questions so didn't know about "accepted answer". If you say that my code will be executed only once every 10 minutes , there should not be the error? Anyway,wait and see tomorrow.

[dpb]

If you don't get the error manually, there's nothing in the code for the daily task that is going to be a problem unless the task is scheduled for a time that is inside the window after the periodic updating has occurred within the 15 sec window.

You could add a check that the current time is greater than 15 sec after the last read timestamp and if not, do a pause() for long enough to satisfy the refresh cycle delay.

As far as the forum, the intent is that Answers are solutions to the Question raised of which there may be like cats, multiple ways of skinning. "Accepted" is way to provide an indicator there is a solution to the question that is satisfactory as an indicator to the community as well as provide the recognition to the contributor.

[William Glass]

See results.txt

I added to timestamps to the code near the end

[dpb]

Well, that's a kick in the head, isn't it? I've never used thingSpeak so no real hands-on experience but the AI 'bot says it's possible that despite the documentation to the contrary, it is treating the read and write as same for the channel access. If that is the case, adding a

pause(20)

after the read before the write operation should make the symptom disappear.

The other alternative would be to write the summary statistics to a second independent channel.

The last thing would be if somehow whatever other process is updating the routine data has the channel accessed in the background that isn't visible at all from this side; we have no information at all on what/how/where the other data are coming from.

[Christopher Stapels]

I think this seems consistant with the behavior you are seing. This line

[data timestamps]= thingSpeakRead(yyyyy, 'NumPoints', 1, 'Fields', 1);
disp(timestamps);

gets the last time stamp in the channel.

04-Nov-2026 16:10:03

You said you ran the execution at 4:10, but the last time stamp is at 4:10 and 3 seconds. That seems to be within 15 seconds, though it actually seems to be after the present time of 4:10. Time controls may be scheduled at the intended time, but it is possible that they run a little late. Can you also output datetime("now") so we know the present time when this happens? It definitely seems to me htat there is data written to the channel right about the same time that you execute this code, thus the frequency rejection.

[dpb]

I guess I misread the timestamp @Christopher Stapels :>)

[Christopher Stapels]

no worries @dpb In my time zone we are still reeling from daylight savings adjustments, so most times are read wrong ;). BTW I did want to point out that reads arent ever treated as writes with respect to rate limits, though you arent crazy to think of it.

[dpb]

Well, I knew weren't supposed to be and that AI can make up stuff out of the ether...good to have confirmation there aren't other circumstances; undoubtedly there was a posting somewhere that drew that conclusion it picked up on as fact.

We shifted as well, thankfully. On the farm, wish they would set at Standard and leave it alone... :>) It's the sun that controls the time of day, not the clock...when it's 11PM by the clock and the sun isn't much yet under the yardarm, it just ain't right when have to match up to something on town time.

[William Glass]

" if that is the case, adding a pause(20) after the read before the write operation should make the symptom disappear. The other alternative would be to write the summary statistics to a second independent channel. The last thing would be if somehow whatever other process is updating the routine data has the channel accessed in the background that isn't visible at all from this side; we have no information at all on what/how/where the other data are coming from."

Well, I still have the same error with the pause and I am already writing the stats to another channel. In the meantime, I have done this processing on my ESP32 used for other stuff as well. It works fine.

[dpb]

Very difficult to diagnose without access and your postings don't show the diagnostics to be able to see sufficient details as @Christopher Stapels noted. There's clearly a conflict from somewhere; just can't tell precisely the origin remotely, particularly since there's the other component behind the curtain playing the part of the great and powerful Oz.

May have to submit this to Mathworks as an official support request at <Product Support Page> so can share the details sufficiently to be able to track down the issue.

[William Glass]

Well, I will stop on this issue now. By doing all this processing on my hardware, I am getting the results I need. Thank you for trying to help me. I think there is a bug in the thingspeak TimeControl or MatlabAnalysis or the way I'm using it. If someone on your side is interested in continuing this investigation, it would be useful for all. The test is really quite simple to set up.

1. create channel1 & channel2
2. send some data to channel1 using https://api.thingspeak.com/update?api_key=xxxxx&field1=yyyy
3. trigger a MatlabAnalysis code using recurrent dayly hour and minute.
4. the MatlabAnalysis code using https://api.thingspeak.com/channels/yyyyyy/fields/1.json?results=N will read these samples then calculate the avg and sd
5. the MatlabAnalysis will then send avg and sd to channel2 using https://api.thingspeak.com/update?api_key=zzzzzz&field1=avg&field2=sd

That's what I tried to do with no success but Thanks again anyway!

[dpb]

That or the real thing with your specific hardware setup is what you should send to MathWorks.

The Answers forum is, while supported by MathWorks, not an official support channel; occasionally a MathWorks staffer will chime in, but that's also a volunteer thing, not any required duty to follow up if other daily duties interfere.

[Vinod]

Some recommendation when using MATLAB in your timecontrols -- using thingSpeakRead and thingSpeakWrite function instead of using the REST API directly. It is more efficient and has error handling for different cases.

That said, the issue you are likely running into is that you're writing into channels too frequently than your free license allows (once every 15 seconds). If you purchases a license you could update your channel every second. Alternatively, try putting a pause(15) in your MATLAB code in your timecontrol. Does that address your issue?

[William Glass]

DB

"That or the real thing with your specific hardware setup is what you should send to MathWorks.

The Answers forum is, while supported by MathWorks, not an official support channel; occasionally a MathWorks staffer will chime in, but that's also a volunteer thing, not any required duty to follow up if other daily duties interfere."

So who and where can I get to a MathWorks staffer? I have simplified my MatlabAnalysis code and still getting errors. All he has to do is create a channel with 2 fields, read my public channel with my simplified MatlabAnalysis code and set up a TimeControl to execute it. See attachmeents.

[dpb]

Submit this to Mathworks as an official support request at <Product Support Page>. There's link at to RH side of the MATLAB window as well.

I strongly suspect there's something going on with the secondary hardware communications channel besides just the analysis code.

[Christopher Stapels]

@dpb since the user mentioned using the 15 second window, I think the user is on the free tier. If so, they are not eligible to get official MathWorks support other than what we can give here. I do think we can figure this out thoguh with the correct information from @William Glass.

[William Glass]

DB "I strongly suspect there's something going on with the secondary hardware communications channel besides just the analysis code."

Nope no secondary HW for this latest test. Just reading channel data(updated by the HW only every hour) and trying to write avg and sd to another channel with my Matlab code. Again, manually works fine.

OK, I'll contact Mathworks.

[dpb]

NOTA BENE: Unfortunately as @Christopher Stapels notes above, the use of the free channel isn't supported as service request. I wasn't ware of that limitation, sorry to have misled.

All I can then suggest is to completely instrument the code to ensure about all the times when it runs automagically instead of manually.

[Christopher Stapels]

Im trying out the code and workflow to see if I can spot the error, and Vinod added some helpful suggestions. If you filed a support request, they would probaby ask Vinod or me to help anyway, so this isn't too bad a route.

[William Glass]

DB

"NOTA BENE: Unfortunately as @Christopher Stapels notes above, the use of the free channel isn't supported as service request. I wasn't ware of that limitation, sorry to have misled.

All I can then suggest is to completely instrument the code to ensure about all the times when it runs automagically instead of manually."

Well, I was just trying to help Matlab folks even though I'm using free channels. I still think there is a bug in either the TimeControl or MatlabAnalysis. As I said earlier, I had no intention of continuing because my hardware performs these same tasks with success. BTW, all Matlab tests that I have described never function automatically.

[Christopher Stapels]

I was able to test using your channel data and your code (but writing to my channel that I used to use for counting players coming to the hockey game). I have a staff license, not a free license, but used a timecontrol to triger this. I used the thingSpeakRead function in the latest code you provided (not the API call) How do you get the output with the fail message? Does that come from the timeControl Appp feedback?

YourChannelID=3266231;
YourWriteKey='xxxxxxxxxxxxxxxx';
channelID =  2787477; 
data= thingSpeakRead(channelID, 'NumPoints', 100, 'Fields',5);
isOK=isfinite(data);    % valid data logical addressing vector
data=data(isOK);        % use logical addressing vector directly, no need for find() here
data
% Calculate the average
avgValue = mean(data);
% display the aveage
disp(['mean: ' num2str(avgValue) ' cm']);
% calcul the std deviation
sd=std(data,1); 
%display the std deviation
disp(['sd: ' num2str(sd) ' cm']);
thingSpeakWrite(YourChannelID,[avgValue,sd],'Fields',[1,2],'WriteKey',YourWriteKey);

[William Glass]

here is the error in the MatlabAnalysis App below:

data =

0

-0.2000

0

-0.1000

-0.4000

-0.4000

-0.4000

-0.4000

-0.5000

-0.5000

-0.5000

-0.5000

-0.5000

mean: -0.33846 cm

sd: 0.18621 cm

Error using test (line 14)

Requests are too frequent. For further information, see Limitations in the documentation.

Answer 2

[dpb]

One of two possible issues could trigger the observed behavior. The first would be the TimeControl is using the Recurrence setting on "Hour" instead of "Day". You should not see an "Every" field when select "Day" but is/will be replaced by the "Time" field which should then be 06:00.

Alternatively, you may have a correctly formatted TimeControl, but since ThingSpeak allows up to 12 active TimeControls, it is easy have other schedule daemons left running in the background from prior testing. Select "Apps > TimeControl" and ensure there are not multiple entries for the desired MATLAB app. Delete or make inactive any duplicates that might show up there.

That should prevent the application from being either scheduled multiple times or executing more than once when it is executed/called/scheduled.

I took the liberty of reducing the MATLAB code just a little to eliminate some unneeded temporaries

NHRS=6;
disp(['process the last ' num2str(NHRS) ' hours of pool level measurements']);  
channelID = xxxxxx; 
[data ts]= thingSpeakRead(channelID, 'NumPoints', 100, 'Fields', 5);    % only ts was used, don't need to copy 
isOK=isfinite(data);    % valid data logical addressing vector
data=data(isOK);        % use logical addressing vector directly, no need for find() here
ts=ts(isOK);            % ditto for timestamps
N=nnz(isOK);            % how many were saved 
[data2]=data(N-NHRS+1:N);   % NOTE: could replace N here with internal keyword 'end'
ts2=ts(N);
%disp('last 24 pool data levels');
%disp(data2);
disp([newline 'time stamp of last pool level measurement']);
disp(ts2);
% Calculate the average
avgValue = mean(data2);
% display the aveage
disp(['mean: ' num2str(avgValue) ' cm']);
% calcul the std deviation
sd=std(data2,1); 
%display the std deviation
disp(['sd: ' num2str(sd) ' cm']);
thingSpeakWrite(xxxxxx,[avgValue,sd],'WriteKey','xxxxxx');