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Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue

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"Hans-Peter Diettrich"  wrote in message 
news:e1o5msFhoooU2@mid.individual.net...

> P E Schoen schrieb:

>> I tried various settings for the serial port component with inconsistent 
>> results. What is consistent is that errors always start when the 
>> CommBuffer is nearly full and the data must be split to fill the buffer 
>> and then start again at the beginning. I may need to check my arithmetic.

> Can't you use multiple buffers, to eliminate the moving of data?

Much of this code dates back to around 1996-1999 when I first tried making 
an application for Windows using Borland C++, and my first use of Borland 
Delphi 4 seems to be around 2003, when a consultant for another project 
showed me how to use it. I think I purchased Delphi and BC++ around 1998.

I'm not sure how multiple buffers would help. The serial port component has 
its own inBuffer which I have set to 48,000 bytes, or enough for 10 seconds 
of data. There is probably another small buffer at a lower level (there is 
an FTempInBuffer which is a pointer to data space allotted to 
FInBufferSize). The actual reading of data is accomplished by using:

nRead := 0;
nToRead := comStat.cbInQue;
if (nToRead > 0) and ReadFile( FHandle, FTempInBuffer^, nToRead, nRead, 
nil ) then
  if (nRead <> 0) and Assigned(FOnReceiveData) then
    FOnReceiveData( Self, FTempInBuffer, nRead );

So it does not appear that the FTempInBuffer is a circular queue, and thus I 
need to implement that in my own code using my CommBuffer[]. I could 
probably use much smaller values for the buffer sizes, but that's not really 
an issue these days when most computers have at least 2g of memory. The 
RxDataCount displayed in my status dialog is usually 280-390 bytes, which 
may depend on the PollingDelay which I have set at 50 mSec. At 4800 char/sec 
that is 240 characters. The extra characters likely occur during the buffer 
processing procedures.

I am doing additional processing in a procedure called by a timer set at 
50-250 mSec. So that may account for more delays and accumulation of data in 
the buffers. My MaxRxdCount after 10 minutes is now 1758. I have found that 
other Windows processes can increase this number, but so far it does not 
seem to lose data.

Quite a lot of real time processing occurs during these update intervals. 
Character pairs are read from the CommBuffer circular queue, and are parsed 
to verify their validity according to the extra two bits in each character, 
while the remaining 6 bits in each are concatenated to form a 12 bit 
integer. The ADC is only 10 bits but I designed the system to use 12 bits if 
needed. The value is shifted by 2048 to get a signed integer.

The absolute value is compared to a threshold value and a number of samples 
to determine if the value (of current) is enough to indicate that a test is 
in progress. If so, a small circular queue is used for pre-trigger data and 
added to a Waveform data buffer (like a digital storage scope). When the 
value drops below threshold for a number of samples, the actual start and 
stop points of the waveform are calculated, and a true RMS computation is 
performed to give the value of current in the pulse. This may be repeated 
for up to five pulses of 60 Hz current in a single test, with off times of 
as long as 20 seconds (although usually 1 or 2).

Meanwhile, the true RMS value of the samples in each update interval is 
computed and displayed on the screen, giving a continuous RMS value at all 
times. The sampling intervals of 50, 100, 150, 200, and 250 mSec are chosen 
to use an integral number of zero crossings for either 50 or 60 Hz. At 2400 
samples per second, 50 mSec is 120 samples, and corresponds to 3 cycles at 
60 Hz or 2.5 cycles at 50 Hz. This measuring technique is used in DMMs to 
cancel the effects of line voltage noise. It also produces consistent true 
RMS readings when the start and end of the sampling period are not 
synchronized to the zero crossings.

You may have already "left the building" at this point, unless you find this 
sort of discussion interesting. I have been involved in the measurement of 
power line frequency current and voltage signals for a LONG time, close to 
40 years. Technology has changed since then, from mostly analog methods, 
then ADCs with early microprocessors like the 8085 and Z80, then signal 
processing boards with MSDOS, and now PICs and DSPs with Windows 10 or other 
OS.

Thanks for your valued suggestions and time.

Paul 

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Delphi D4: using pointers to transfer data from COMM queue to circular queue "P E Schoen" <paul@pstech-inc.com> - 2016-08-19 02:19 -0400
  Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue "P E Schoen" <paul@pstech-inc.com> - 2016-08-19 03:58 -0400
    Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue "P E Schoen" <paul@pstech-inc.com> - 2016-08-19 04:42 -0400
      Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue Hans-Peter Diettrich <DrDiettrich1@aol.com> - 2016-08-19 12:34 +0200
    Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue Hans-Peter Diettrich <DrDiettrich1@aol.com> - 2016-08-19 12:30 +0200
      Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue "P E Schoen" <paul@pstech-inc.com> - 2016-08-19 20:54 -0400
        Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue Hans-Peter Diettrich <DrDiettrich1@aol.com> - 2016-08-20 12:43 +0200
          Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue "P E Schoen" <paul@pstech-inc.com> - 2016-08-20 19:15 -0400
            Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue Hans-Peter Diettrich <DrDiettrich1@aol.com> - 2016-08-21 12:50 +0200
              Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue "P E Schoen" <paul@pstech-inc.com> - 2016-08-22 07:12 -0400
  Re: Delphi D4: using pointers to transfer data from COMM queue to circular queue Hans-Peter Diettrich <DrDiettrich1@aol.com> - 2016-08-19 12:27 +0200

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