Infinit analog in record length

[Reinhard]

Hello everyone,

is there an option to specify an infinit record length?

like (which doesn't work)

dwf.FDwfAnalogInRecordLengthSet(hdwf, c_double(-1))

Thanks.

[attila]

Hi @Reinhard

For infinite record you can specify negative number for record length: AnalogIn_Record.py

dwf.FDwfAnalogInRecordLengthSet(hdwf, c_double(-1)) 

 

It looks like for infinite record the lost samples are reported wrongly. Try ignoring this:

...
dwf.FDwfAnalogInStatusRecord(hdwf, byref(cAvailable), byref(cLost), byref(cCorrupted))
#cSamples += cLost.value # ignore for infinite record
#if cLost.value :
#    fLost = 1
...

 

[Reinhard]

@attila Thank you for the answer.

Will this be fixed in a future release?

[attila]

Hi @Reinhard

Sure, it will be fixed.
You have in private message a beta version solving this issue.

[Filippo]

Hi, I am interested in using the AD2 acquisition in continuous record mode.

I would like to know if the issue mentioned here

On 19/12/2017 at 4:11 PM, attila said:

Hi @Reinhard

Sure, it will be fixed.
You have in private message a beta version solving this issue.

has been fixed in the present release 3.7.5 (January 2018).

Could not find any mention of it in the change log: https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/change-logs/3-7-5

It is also not very clear to me the difference between the int *pcdDataLost and int *pcdDataCorrupt counts provided by the FDwfAnalogInStatusRecord() function: aren't they the same thing ? (if 1 sample has been overwritten before the USB readout, I lost 1 sample, thus 1 sample in the buffer i got is corrupted). The SDK reference manual did not make it clear to me.

Can someone please help me spotting out the difference? Actually I just want to know that no sample has been dropped between my buffer readout cycles, which of the two variables should I take confidently into account ?

Thank you very much,

Filippo

 

[attila]

Hi @Filippo

You can consider both as error and reduce the acquisition frequency.
During recording the device buffer is used as a circularly written memory.
The corrupt indicates that the read data could have been altered, the device buffer got above 50% full.
The lost indicate how many samples are dropped, device buffer overflow.

FDwfAnalogInStatusRecord(
HDWF hdwf, int *pcdDataAvailable, int *pcdDataLost, int *pcdDataCorrupt)
Parameters:
- hdwf – Interface handle.
- pcdDataAvailable – Pointer to variable to receive the available number of samples.
- pcdDataLost – Pointer to variable to receive the lost samples after the last check.
- pcdDataCorrupt – Pointer to variable to receive the number of samples that could be corrupt.
The function above is used to retrieve information about the recording process. The data loss occurs when the
device acquisition is faster than the read process to PC. In this case, the device recording buffer is filled and data
samples are overwritten. Corrupt samples indicate that the samples have been overwritten by the acquisition
process during the previous read. In this case, try optimizing the loop process for faster execution or reduce the
acquisition frequency or record length to be less than or equal to the device buffer size (record length <= buffer
size/frequency).

[Filippo]

Thank you @attila.