Sending realtime data EMG to my Android via BluetoothLE

[ABG]

Here is the upstream code, which I am weak on:

char sSensorVals[16];
unsigned int nilai_sensor;
unsigned int nilai_sensor2;
...
   {
        lgUpdateTime = millis();
        nilai_sensor = analogRead(A0);     
        nilai_sensor2 = analogRead(A1);
        sprintf(sSensorVals, "%u,%u\0", nilai_sensor, nilai_sensor2);
        switchCharacteristic.writeValue(sSensorVals); //Send value pair to App
}

Here are some stabs in the dark for this code:

• Is 16 bytes enough for the sprintf buffer?
• Does sSensorVals need to be cleared between sprintf calls?
• how does the %u print format work? (Can it be broken with bad input?)
• Does that trailing \0 really work, on both ends of the transmission, to delimit messages?

[ChrisWard]

Some good points!

16 bytes: anologRead() outputs unsigned integers between 0 and 1023

1023,1023\0\0 = 13 UTF-8 string bytes. Note, Sprintf() should add it's own null (\0) but for some unknown reason that can go missing, so imposing another is a belt-and-braces measure. We should test without the extra \0, see below.

sSensorVals: Should not need to be cleared, but there is no harm in doing so.

%u: is a place holder for an unsigned int. That should be bullet proof but it is possible for the sensor to glitch, depending on sensor quality and the environment.

\0: Yes, that seems to be working, Muhammad has a working graph. It is technically not a delimiter but an end-of-string flag. Each value pair is streamed to the App per 1 second (Arduino timing is more accurate than Android timing).

[ABG]

Some more stabs in the dark:

This error text does not appear in the app, so I am going to point the finger at the Kio graph block, because it does not match any AI2 list block complaint I have ever seen before.

I assume the Kio blocks maintain their own internal lists, because their graphs extend across the Canvas and that graph block accepts two points at a time.

I notice there is an initialization call in

but it is not initialized in Screen init, so I suggest adding it:

That hardly makes sense, though, since the graph starts out okay.
Is it possible that the graph extension reaches an internal limit?

Based on the error message alone, I would switch to the AI2 list based graph component, with two input list Chartdata components.

Example:

Create a Temp vs time graph

To show how to normalize time based readings to a particular scale, here is an example of the Drunkard's Walk, for the last 12 seconds: [blocks] charts_last_hour.aia (3.8 KB) [Designer] [initialize global raw_data to] [initialize global time_window_seconds to] [initialize global Y to] [to normalize readings_table scale_in_seconds result] [when btnAddNumber .Click do]

(needs an extra chartData component, does not need normalization.)

[ChrisWard]

@Muhammad_Zulkifli

I've try your change sir, but there is an error, same error

Regarding ABG's comments about the Sketch:
Apart from the latest App Inventor Blocks fix, here is a modified Sketch that clears the sSensorVals string before the next value is applied. Also, '\0' is removed from sprinf(). Hopefully this will be even more robust.

ACTUATOR_COBAK6e.ino (8.3 KB)

[ChrisWard]

@ABG

Some more stabs in the dark:

The error message is triggered by the wonky value passed to the extension.

I think it would be good not to use an extension as there will be no point Juan maintaining it in future, now that App Inventor has it's own charts component.

Does the App Inventor chart allow run-time updates the way Juan's does? It will still require the code to omit wonky values.

[ChrisWard]

... one way to make everything more robust would be to increase the time interval from one second to two seconds.

[Juan_Antonio]

Suppose the app receives...

REAL TIME DATA1
(11,32)
(12,31)
(12,31)
...

Try,,,

[ChrisWard]

Hi Juan - that's actually very similar to earlier code. I think our latest code will ensure that wonky values will not get through to the graph.

[Muhammad_Zulkifli]

@ChrisWard

LED_Control_6E.aia (617.4 KB)

I I've tried it, sir, but I can only catch it once, however the signal changes, it's still the same

[Muhammad_Zulkifli]

@ChrisWard

that's actually very similar to earlier code

Maybe I can try it first sir

[ChrisWard]

@Muhammad_Zulkifli

I've tried it, sir, but I can only catch it once, however the signal changes, it's still the same

Hi Muhammad

Not sure if that's the Sketch or the App - I don't understand what you mean Can you describe the latest situation again (E.aia and E.ino) with the aid of an image?

[ChrisWard]

@Muhammad_Zulkifli

Maybe I can try it first sir

Like our first code, it would let for example "444," and ",444" through.

[Muhammad_Zulkifli]

@ChrisWard

Like our first code

I think the difference is that the .aia files are not showing in the labels
I don't know if I use labels, is there a number that is wonky again or not

[Muhammad_Zulkifli]

@ChrisWard

(E.aia and E.ino)

I use LED_Control_6E.aia and if .ino I use this
ACTUATOR_COBAK6e.ino (8.3 KB)
This is my example

I have turn my Variable resistors and still same writen in lable

[Juan_Antonio]

Have you tried the code I put in in post #139?
Change the max1 and max2 values ​​to 1000.

[ChrisWard]

@Muhammad_Zulkifli

This is my example

Hi Muhammad

I think it may be how the value is sent to the Label - should just overwrite, but it is still adding

1. Change it to this:

2. Also, sprintf() produces a null terminated string, so the App needs to know:

3. Question - are the values streaming on the Arduino Serial Monitor correctly?

[Muhammad_Zulkifli]

@Juan_Antonio

Change the max1 and max2 values ​​to 1000.

I have tried sir.
and same error

[Muhammad_Zulkifli]

@ChrisWard

Change it to this:

About this I have tried sir, this is appearance from my app

@ChrisWard

2. Also, sprintf() produces a null terminated string, so the App needs to know:

How about my button LED sir? is it work although the app I installed this

@ChrisWard

Question - are the values streaming on the Arduino Serial Monitor correctly?

It is corect sir

[ChrisWard]

Hi Muhammed

So the chart is working, just not the updating of the Label.

@Muhammad_Zulkifli

How about my button LED sir? is it work although the app I installed this

I have no idea what you mean

[ChrisWard]

@Muhammad_Zulkifli

About this I have tried sir, this is appearance from my app

Well, we need to see the new Project File.......