Rigol MSO1104 SPI logic analyser decode problem [SOLVED]

[FrankT]

I'm trying to use the SPI decode feature on the logic analyser inputs.  It appears to be decoding a bit on both the rising and falling edges of the clock (See attached picture).

I can get it to work with an analog input,  not a digital one.

Does anyone know if I'm missing a setting?  I couldn't find anything.

[Howardlong]

Is it undersampling?

Try speeding up the trace a notch. The sampling rate for decoding is a lot less than the scope's sampling rate, but it moves up and down with the timebase. Sadly you don't seem to be able to manually adjust the decode sampling rate on this series of scopes.

[FrankT]

Thanks,

I tried that without success.  I looks buggy.  If I switch the clock line from the digital input to an analog input, it works.  If I slow the SPI clock down to 25kHz, I get decoded byte on every clock pulse.

[Howardlong]

Just tried it myself.  Check that, if the SPI decode mode is set to Timeout (rather than CS), the decode timeout is sufficient, or use the CS mode.

It seemed to work for me.

[smgvbest]

Just tried it myself.  Check that, if the SPI decode mode is set to Timeout (rather than CS), the decode timeout is sufficient, or use the CS mode.

It seemed to work for me.

If I understood the OP correctly he is having the issue on the Digital inputs not the analog ones.   from the look of you screen capture your on the analog inputs. 

I could be wrong though.

[Howardlong]

Thank you for the clarification, Sandra, you're right. I'll test again tomorrow, it's late here.

[Howardlong]

I couldn't stop myself, I had to deal with it now, even though it is 0130 here. It looks like my comments are still valid on the LA as well as analogue channels. Firmware is the recently semi-released beta to fix the jitter problem some people were encountering and the AC coupled trigger.


8 bit decode




16 bit decode




Use of CS rather than timeout (default) mode: if you have CS available this makes sense. or you have to fiddle with the Timeout value

[FrankT]

That's good to hear.  Where did you get the semi-released beta?

[smgvbest]

I hope they release this soon.   

[Howardlong]

That's good to hear.  Where did you get the semi-released beta?

It was available for a few days from Rigol about a month ago as a beta to fix the now infamous, if rarely noticed, AC trigger coupling and jitter problem. Unfortunately, for many users it also introduced a new feature where the front panel was very frequently either unresponsive or produced erratic random keypresses at startup, resolved by switching off and on again. There was also no way to return to your previous version.

[FrankT]

The latest firmware, 00.04.02 SP4, has fixed the problem.