generating and reading a custom signal

[ssm]

Dear Help, 

I am generating a custom signal using WaveGen, apply it to DUT and then reading the result using the scope. I know that the speed/rate at which I am reading is limited by the USB and it is recommended not to go beyond 1M. I assumed I am going to lose few samples here and there, but the problem is that I am losing a big chunk of data which it seems more like a sync issue.

Here is the generated signal:

and here is the signal I am reading:

Is there a way to properly sync the AnalogIn and the AnalogOut to avoid such a problem? I am using the AnalogIn to trigger the scope.

here is the relevant part of the code to configure the scope:

1.                     // enable scope channels
2.                     FDwfAnalogInChannelEnableSet(hdwf, -1, true);
3.                     //FDwfAnalogInChannelEnableSet(hdwf, 1, true);
4.                     FDwfAnalogInAcquisitionModeSet(hdwf, acqmodeSingle);
5.                     FDwfAnalogInChannelRangeSet(hdwf, -1, 2);
6.                     // sample rate
7.                     FDwfAnalogInFrequencySet(hdwf, EXP->SampleRates[expNumber]);
8.                     FDwfAnalogInBufferSizeSet(hdwf, AD2ScopeBufferSize);
9.                     FDwfAnalogInChannelOffsetGet(hdwf, 0, &pvoltInOffsetC0);
10.                     FDwfAnalogInChannelOffsetGet(hdwf, 1, &pvoltInOffsetC1);
11.                     // configure trigger
12.                     FDwfAnalogInTriggerSourceSet(hdwf, trigsrcDetectorAnalogIn);
13.                     FDwfAnalogInTriggerAutoTimeoutSet(hdwf, 10.0);
14.                     FDwfAnalogInTriggerTypeSet(hdwf, trigtypeTransition);
15.                     FDwfAnalogInTriggerLevelSet(hdwf, 0.0);
16.                     FDwfAnalogInTriggerConditionSet(hdwf, trigcondRisingPositive);
17.                     FDwfAnalogInChannelFilterSet(hdwf, -1, filterAverage);
18.                     // wait at least 2 seconds with Analog Discovery for the offset to stabilize, before the first reading after device open or offset/range change
19.                     FDwfAnalogInConfigure(hdwf, true, false);
20.                     Wait(EXP->SetupWaitingTime[expNumber]);

here is the wavegen configuration:

FDwfAnalogOutNodeEnableSet(hdwf, 0, AnalogOutNodeCarrier, true);

1.                     // set custom function
2.                     FDwfAnalogOutNodeFunctionSet(hdwf, 0, AnalogOutNodeCarrier, funcCustom);
3.                     // get channel offset
4.                     FDwfAnalogOutNodeOffsetGet(hdwf, 0, AnalogOutNodeCarrier, &pvoltOutOffset);
5.                     // set custom waveform samples, normalized to ±1 values
6.                    FDwfAnalogOutNodeDataSet(hdwf, 0, AnalogOutNodeCarrier, InputFileSamples, NoSamplesInFile);
7.                    FDwfAnalogOutNodeFrequencySet(hdwf, 0, AnalogOutNodeCarrier, EXP->CustomSignalFreq[expNumber]);
8.                    FDwfAnalogOutNodeAmplitudeSet(hdwf, 0, AnalogOutNodeCarrier, EXP->MaxVdd[expNumber]);
9.                     FDwfAnalogOutRepeatSet(hdwf, 0,EXP->RepeatedTimes[expNumber]);
10.                     FDwfAnalogOutConfigure(hdwf, 0, true);
11.                     Wait(EXP->SetupWaitingTime[expNumber])

this is the Acquisition code:

1.                    // begin acquisition
2.                     FDwfAnalogInConfigure(hdwf, false, true);
3.                     FDwfAnalogOutConfigure(hdwf, 0, true);
4.                     while(true){
5.                         FDwfAnalogInStatus(hdwf, true, &sts);
6.                             if(sts == DwfStateDone) {
7.                                 break;
8.                             }
9.                         //Wait(0.001);
10.                     }
11.                     FDwfAnalogInConfigure(hdwf, false, false);
12.                     FDwfAnalogOutConfigure(hdwf, 0, false);
13.                     FDwfAnalogInStatusData(hdwf, 0, EXP->ScopeC0Samples, AD2ScopeBufferSize);
14.                     FDwfAnalogInStatusData(hdwf, 1, EXP->ScopeC1Samples, AD2ScopeBufferSize);

Note that this problem is happening only at certain sampling frequencies, even >2M still things are working.

the scope buffer here is 8192 and wavegen buffer is 4096,

sampling rate is 4194304 for the scope, and 1024 or 4194304/4096 for the wavegen signal 

thank you for the help

ssm

Example of out of sync signal:

example of part of the signal is gone:

here I used a very short pulse (5 sample points) at the start of the custom signal to trigger the AnalogIn, but this pulse is dragged for a long time, not sure why:

 

 

[attila]

Hi @ssm

The FDwfAnalogOutNodeFrequency for standard and custom waveform = 1 / the entire waveform period
If you have a custom waveform with 2000 samples and specify 1kHz, the sample rate will be 2MHz.

By default the signal will be generated continuously until stopped, the run time is 0 (infinite)
If you want to have finite repeat time first you should specify a run time, like:
FDwfAnalogOutRunSet(hdwf, 0, 1.0/secPeriod secPeriod)
FDwfAnalogOutRepeatSet(hdwf, 0, 100)
You can also specify trigger, wait...

[attila]

Hi @ssm

The acquisition rate is limited only for recording. Normal captures up to 8/16ki with AD can go up to 100MHz.
You are missing the: FDwfAnalogOutNodeEnableSet(hdwf, 0, AnalogOutNodeCarrier, true)
The custom waveform should be normalized to +/-1 values
Note the FDwfAnalogOutNodeFrequencySet refers to the waveform period and not sample rate.
The FDwfAnalogInConfigure(hdwf, false, false); at the end is not required.
The wait is only recommended before performing the first capture, after connecting to the device or changing the offset level in order this to settle.

[ssm]

>> The acquisition rate is limited only for recording. Normal captures up to 8/16ki with AD can go up to 100MHz.

so I understand from this I should not have any missing samples
>> You are missing the: FDwfAnalogOutNodeEnableSet(hdwf, 0, AnalogOutNodeCarrier, true)

I added this part, missed few lines of code there
>> The custom waveform should be normalized to +/-1 values

they are normalized
>> Note the FDwfAnalogOutNodeFrequencySet refers to the waveform period and not sample rate.

this part still not very clear, is it how many times the uploaded signal is repeated?
>> The FDwfAnalogInConfigure(hdwf, false, false); at the end is not required.

I will take it out
 

thank you again for your help

[ssm]

thank you attila for the great help,

ssm

[ssm]

I am still getting shifted or out of sync problems, sometimes a chunk of the signal is gone. I added pictures in the main question,

Is there a way to fix this issue or I just have to live with it?

thank you for the help

 

[attila]

Hi @ssm

The analog-out could be stopped, restarted... I don't know how much run time have you specified, use:
FDwfAnalogOutRunSet(hdwf, 0, 1.0 / EXP->CustomSignalFreq[expNumber])

The out-in you can synchronize with:
FDwfAnalogInTriggerSourceSet(hdwf, trigsrcAnalogOut1)

Relative to middle, zero is middle of capture:
FDwfAnalogInTriggerPositionSet(hdwf, 0)

Trigger to be on the left of the capture use:
FDwfAnalogInTriggerPositionSet(hdwf, 0.5 * AD2ScopeBufferSize / EXP->SampleRates[expNumber] )

[ssm]

the mistake was here:

FDwfAnalogInTriggerSourceSet(hdwf, trigsrcDetectorAnalogIn);

not sure why I used trigsrcDetectorAnalogIn instead of trigsrcAnalogOut1

FDwfAnalogInTriggerSourceSet(hdwf, trigsrcAnalogOut1)

working perfectly now.

thanks a million for the great help

ssm