C++Builder3 -putting values into an array

Posted on 2001-06-09
Last Modified: 2008-03-17
Data Acquistion program written using Borlands C++builder3:
 I am using a driver function to return a value which I then intend to plot using TPerformanceGraph. I would like to lable the axis (not an included feature of TPerformanceGraph), particularly the x-axis,which will be time.

void __fastcall TForm1::Button2Click(TObject *Sender)

   if (gnNumOfSubdevices == 0)

                            (LONG far *)&DriverHandle);

                               (LONG far *)&DriverHandle);

            ptAIVoltageIn.chan = gwChannel;
            ptAIVoltageIn.gain = ptAIConfig.DasGain;
            ptAIVoltageIn.TrigMode = 0; // internal trigger
            ptAIVoltageIn.voltage = (FLOAT far *)&fVoltage;


        data[i] =?????????????????????????????????

       PerformanceGraph1->DataPoint(clRed,data[i] );

I need to put values returned by DRV_AIVoltageIn() into my data array, but dont know how.
The closest I've come has been with the following code:
data[i] = *(ptAIVoltageIn.voltage);
...which only allows me to compile, but causes a crash because of illegal use of a float blah blah blah. (makes my eyes hurt to read it.
Here's some info on the driver functions:

status = DRV_AIVoltageIn(DriverHandle, lpAIVoltageIn)

Reads an analog input channel and returns the result scaled to a voltage. (units = volts)
Name            Direction     Type           Description

DriverHandle     Input             long          assigned by

lpVoltageIn   Input/Output  long pointer to    the storage
                             PT_AIVoltageIn    address for                                            chan,gain  
                                              TrigMode and

1) SUCCESS if successful
2) InvalidDriverHandle if DriverHandle = NULL
3) AIConversionFailed if A/D conversion failed
4) DataNotReady if TrigMode=1 and data is not ready
5) AIScale return code

           typedef struct tagPT_AIVoltageIn
     USHORT      chan;
     USHORT      gain;
     USHORT      TrigMode;
     FLOAT far   *voltage;

       } PT_AIVoltageIn, FAR * LPT_AIVoltageIn;

PT_AIVoltageIn is used by DRV_AIVoltageIn function .

Name     Direction     Type          Description
chan     Input         unsignedshort     the sampled channel

gain     Input        unsigned short        gain code

TrigMode  Input         unsigned short     trigger mode

voltage       Output    long pointer
                   to floating-point     measured voltage
                                        returned, scaled
                                        to units of volts

Thanks again for all your help,
Question by:RLawless
LVL 22

Accepted Solution

nietod earned 300 total points
ID: 6171004
>>  Because my values are coming from a for loop the timing may
>> vary if there is other demands on the system (?).
Thsi could be a gigantic effect.  Your app could be suspended for long periods of time, like say a tenth of a second.  That doesn't sound like mutch, but you might be able to collect 1000 data points in that time.  So it has a drastic effect on the data.

Your best bet is to use external hardware to collect the data and provide it to the computer.  Or to use an external device that provides both a data point and a time at which it was collected.

Less good would be to remove the assumption that the values are equally spaced (in time) and collect both the time and the values.  The problem is that you have assume that the program is not suspended between the time the time is obtained and the value is obtained.  There's no way to prevent that.  however increasing the priority fo the thread will help.

Expert Comment

ID: 6181005
Hi RLawless,

Generally, when I encounter this problem I use the following snippet.

memcpy( &( ( *data )[ i] ), (void*)&ptAIVoltageIn.voltage, sizeof( ptAIVoltageIn.voltage) );

I'm posting this as a comment as im not 100% sure that it'll work in your case as there is insufficient code to compile reliably.

You can award some points if it works but let me know either way.

Best of luck

LVL 11

Expert Comment

ID: 6811732
I think you forgot this question. I will ask Community Support to close it unless you finalize it within 7 days.
Unless there is objection or further activity,  I will suggest to accept "nietod" comment(s) as an answer.

If you think your question was not answered at all, you can post a request in Community support (please include this link) to refund your points.
The link to the Community Support area is:

Please do not accept this comment as an answer!

Expert Comment

ID: 6828363
Force/accepted by

Community Support Moderator
Experts Exchange

Featured Post

Master Your Team's Linux and Cloud Stack

Come see why top tech companies like Mailchimp and Media Temple use Linux Academy to build their employee training programs.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Written by John Humphreys C++ Threading and the POSIX Library This article will cover the basic information that you need to know in order to make use of the POSIX threading library available for C and C++ on UNIX and most Linux systems.   [s…
  Included as part of the C++ Standard Template Library (STL) is a collection of generic containers. Each of these containers serves a different purpose and has different pros and cons. It is often difficult to decide which container to use and …
The viewer will learn how to pass data into a function in C++. This is one step further in using functions. Instead of only printing text onto the console, the function will be able to perform calculations with argumentents given by the user.
The viewer will learn how to clear a vector as well as how to detect empty vectors in C++.

803 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question