Digital Discovery Play Mode not outputting

[AlanB]

I've recently come back to my Digital Discovery after a few months away.  I installed the latest version of WaveForms (3.18.49) and got started...

I tried running my Python script (which I'm sure *used* to work) to load a signal and play it back with Play mode.  While it appeared to run without error, I was getting inconsistent output on the pins - usually nothing at all, but I think I once had a garbled version of the output I was expecting.

I've gone to try running the example applications to try to understand the problem, and I'm not getting what I expect there either.  Running the file "DigitalDiscovery_Play.py" from the SDK examples doesn't appear to give any output at all on the pins (I have a logic analyser connected to most of the pins labelled 24-31).  It does print out the following:

DWF Version: b'3.18.49'
Opening first device
Configuring Digital Out...
Samples:134217728 Rate:100000000.0Hz  Period:1.34217728s

Should I expect more than this?  Is installing older versions of the SDK likely to be the best route forwards?

[attila]

Hi @AlanB

Here you can find the new version in which there is no need for DataSet after Configure:

Try with param stop. With run option, if the previously used application exited with shutdown the IO voltage level translators remain disabled.
dwf.FDwfParamSet(DwfParamOnClose, c_int(1)) # 0 = run, 1 = stop, 2 = shutdown
If the run option is needed, after open use the following to set the IO voltage and enable the translators:
# set digital voltage between 1.2 and 3.3V
dwf.FDwfAnalogIOChannelNodeSet(hdwf, c_int(0), c_int(0), c_double(3.3))
dwf.FDwfAnalogIOConfigure(hdwf, c_int(0)) 

The Digital Discovery play output captured with Analog Discovery:

[attila]

Hi @AlanB

Until this bug is solved use the following workaround, call DataSet twice, before and after Configure.
FDwfDigitalOutPlayDataSet
FDwfDigitalOutConfigure
FDwfDigitalOutPlayDataSet

[AlanB]

On 8/29/2022 at 9:45 AM, attila said:

Until this bug is solved use the following workaround, call DataSet twice, before and after Configure.
FDwfDigitalOutPlayDataSet
FDwfDigitalOutConfigure
FDwfDigitalOutPlayDataSet

I have copied line 64 of DigitalDiscovery_Play.py and placed it after the Configure call, as follows:

# set play data array of 16 bit samples
dwf.FDwfDigitalOutPlayDataSet(hdwf, byref(rgwPlay), c_int(16), c_int(int(nPlay)))

print("Starting Digital Out...")
dwf.FDwfDigitalOutConfigure(hdwf, c_int(1))
dwf.FDwfDigitalOutPlayDataSet(hdwf, byref(rgwPlay), c_int(16), c_int(int(nPlay)))

But I'm still not seeing any output on the output pins.  Do I need to use different parameters for the two calls to DataSet?

[attila]

Hi @AlanB

The following is working for me, with internal loopback on DIO lines: DigitalDiscovery_PlayRecord.py

[AlanB]

I can see the same graph when I run your script.  I don't see any output on a logic analyzer on the IO lines.  Can you confirm which lines (as labelled on the unit) should be being driven using that script?

[AlanB]

Thanks for the suggestions.  With the updated version of the SDK (3.18.50) and the change to param stop-on-close, I can see the expected output from the DigitalDiscovery_PlayRecord.py example as you've shown.  I haven't had the same success with DigitalDiscovery_Play.py (yet).  However, my original Python scripts appear to have started working again, outputting the expected patterns, so the latest SDK version is the one I'll carry on with.