Smart device real time application

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Hello thare,i'm working on a real time application for smart device with C#. i want to send data every 37 millis seconde.
i did a program that send data every 37 millis-second with the function thread.sleep(37).
but when i see the data on the oscilloscope , the time between every data sent is not 37 millis-second . so i didn't send data on a real time. i want to know if there is a methode to send data exactly every 37 seconde without interruption by other processe. is there a way tow work wuth a thread and high priority.?? to make the application real time.

the goal is to send exactly the data evey 37 millis-second without interruption. i'm working on visula studio 2008, c# smart device.

thanks :)

What I have tried:

C#

main 
{
//loop here 
Serial.write(data)
thread.sleep(37)
//
}

Posted 5-May-16 5:00am

Jammes_Ca

Updated 5-May-16 21:18pm

Santosh Kokatnur

v3

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Sergey Alexandrovich Kryukov · Answer 1 · 2016-05-05T05:05:00

Solution 1

You cannot do such things, because the OS is not a real-time OS. One possible solution is to plot data as a scatter plot, passing both measurement and the time stamp of measurement event. You don't have to use a real oscilloscope; you can always use the on-screen chart to show data.

Sorry, but true real-time problems are not solvable at this level. There are different solutions based on specialized hardware.

—SA

Posted 5-May-16 5:05am

Sergey Alexandrovich Kryukov

Comments

Jammes_Ca 5-May-16 11:13am

I didn't understand your solution, could you give me more detail. or write me some code please, i am newer :)

Sergey Alexandrovich Kryukov 5-May-16 11:22am

This is not a full solution, just an idea: perhaps you don't really need real time so badly. You cannot achieve any real-time qualities on this level.

Perhaps you don't need exact time, but need a correct function of some measurement values s(t), where t is time, defined in several points in time. Those points can be equidistant in time (which you cannot achieve), or not (which is quite realistic scenario). Deliver not just s-values (based on 27 millisecond assumption), but pair of numbers: signal and time. Show the points on the plot not assuming that the points in time are equidistant. It's called "scatter plot".

Is it clear?

—SA

Sergey Alexandrovich Kryukov 5-May-16 11:22am

...

Jammes_Ca 5-May-16 11:30am

i understand, but i should send data every 37ms, or the time betweene two datas is 37 seconde, because i send those data to an IR sensor, se the ir sensor he likes receving data in 37 ms intervale. the goal is the data who will be sent, they should 37ms interval between every data sent

Sergey Alexandrovich Kryukov 5-May-16 11:36am

From your application code? Then forget about this "should", period. Sorry. You need a hardware solution.
If you describe your ultimate goals, perhaps I would advise some alternative.
—SA

Jammes_Ca 5-May-16 11:53am

Ok i will describe the project, there is an electronic card, that has an IR sensor and a micro controleur, and ther is a "pda"" mx workabout" that communicate with electronic card through IR sensor, the communication based on a standar serial port communication."1 bit start 8 bits data 1 bit parity 1 bit stop"

now we have a new genertion of a pda is a "PIDION BIP6000" so we want to communicate with this card with the pidion and not with the old generation of pda which based on dos application.

so to communicate with this electronic card we should send data to it.
the interval between 2 data is 37 ms.
for example i send 0x35 0x80. to blink the led wich in the electronic card.
and the time between the 0x35 and 0x80 is 37 ms.

the problem is we have not source code of th old pda"mx workabout". we don't know if it has a real time operatin gsystem or no.

so the goal is to communicate with this card with sendind regular time of data

Sergey Alexandrovich Kryukov 5-May-16 12:02pm

Explain one more thing: what is "card" exactly? What is inserted in a computer, what is outside. Please, whole hardware setup. Second thing: the goal of all this activity. Real, ultimate goal. Why communicating with this card? What do you want to achieve from it. "so the goal is to communicate with this card with sending regular time of data" is never an ultimate goal, it's always an intermediate goal. (By the way, you did not even specify exact time precision.) And you cannot send data from Windows at exact regular intervals. And I cannot be 100% sure that the card really requires that, even with certain time precision. I know this is a RFID device...
—SA

Jammes_Ca 5-May-16 12:15pm

about the card we d'ont know anything how it's works. but we know that card works well with the "mx workabout" and also we have not the source code of the program that run on mx.
this card has data, the ir sensor on this card count how many personne enter in a room, so the ir sensor detecte a presence and store the data in the micro controleur.

Now we have a new generation of a pda, and we want to do the same application that was in the old pda.
we have all the data code to communicate with this card, for axamlpe the data 0x88 0x96 start the communication between the electronic card and the PDA.

the probleme is, we sent the same data with the PIDION. but the electronic card , didn"t answer. and after several expirementation. we recognize that we have 2 problem.
first problem is the frequency of pcm modulation IR of the pidion is low than th IR if "mx workabout". so we should change the modulation of the pidion

second probleme. we did test with the "mx workabout" we send data with the mx and we visualise the data on the osciliscope and we find the time between 2 data is 37ms.

so this is why i told you i have to send data evey 37ms.

we have no idea about the card and we don"t know how it's work.

Sergey Alexandrovich Kryukov 5-May-16 12:23pm

You apparently stuck. It looks like you have insufficient information about the device. I only can tell you that you cannot guarantee regular time intervals, even with some predefined precision. I'm 100% sure you did not guarantee it with for the older device. This is a stochastic process, with some good responsiveness of the system, which you can make better or worse, but never can guarantee any predefined time constraints. If your device worked well, it means that it was somewhat tolerant to the poor precision of timing.

Do you have any change to get manufacturer's help?

Again, "I have to send data every 37ms" is just the misconception. There is no such thing in nature. Even if you "have to", you have to do it to certain precision, which you would need to know. Also, it sounds very questionable, perhaps, you don't have to do so. If you really had, I would call it a fatal manufacturer's defect. Such devices don't inherently need in real-time processing; real-time requirements would simply render them unusable, that's all.

After all, if the manufacturer cannot solve your problem, return the devices and demand you money back.

—SA

Jammes_Ca 5-May-16 12:27pm

i told you with the old device we see time between data is 37 ms
and i have another question, tell me how i can change the IR pcm modulation ???
i want the ir PCM MODULTAION GET 150KHZ. actualy he hase 19 khz

Sergey Alexandrovich Kryukov 5-May-16 12:29pm

No — what?
I have no idea how to change the modulation. Address to the manufacturer.
—SA

Jammes_Ca 5-May-16 12:31pm

i edited my answer. i said no for your question "Do you have any change to get manufacturer's help?"

Jammes_Ca 5-May-16 12:31pm

and how can i send data with a regular time ?? even 37 or 40 or 200 ms have you an idea ?

Sergey Alexandrovich Kryukov 5-May-16 13:17pm

The whole idea is wrong.
—SA

Jammes_Ca 5-May-16 15:33pm

how ?

Sergey Alexandrovich Kryukov 5-May-16 15:57pm

You should through out the idea of reliably repeated event with regular time intervals. This is impossible, or possible only with certain probability. Hardware control/acquisition based on not real-time systems should be based on ether independence on timing (read about race condition) or measuring the point of real time and supplying it along with data. The accurate device for time inquiry is the class Stopwatch. That's all.
—SA

Jammes_Ca 5-May-16 16:08pm

i told you, i don't care about the hardwar, i want just send data from the IR of a pidion. maube there is a technique to force non real time to a real time os. thread with high priority

Sergey Alexandrovich Kryukov 5-May-16 16:17pm

It does not matter what you care about and what not. What you want to do is a wrong idea. Case closed.
—SA

Jammes_Ca 5-May-16 16:25pm

i told you with tread wz can get a high perfeormance