Parsing Logic Analyzer with Script?

[John Kozell]

Hi folks,

I'm currently hacking a 433Mhz temperature probe, and attempting to intercept the reading using a standard 433Mhz receiver, such as the Sparkfun RF Link Receiver.

Using WaveForms (desktop) I can record the Logic Analyzer output, and can see the single fine. I'm currently in the process of parsing the bit stream. The signal is repeated every 59 seconds. However I need more samples, and the manual translation of the square wave to 0/1's is tedious and time consuming (and error prone).

I'd like to create a script that will read the 'repeated' (not recorded, realtime) Logic1 data, look for the periodic transmission bursts, convert the encoded waves to a binary character stream (ex: "0101001010") and print it to the screen (or log to file).

Is this approach possible, in the way I'm thinking of it? Or is there an easier/better way to approach it?

Also, I haven't been able to find many Script samples around the Logic# object. I understand it is similar to the Scope# (for example), but still a closer sample wound be great.

Any tips/suggestions?

Thanks

-John

[attila]

Hi @John Kozell

In case this protocol is UART, CAN, 1Wire... you can add such interpreter in WaveForms Logic Analyzer.
If you are familiar with programming you can add custom interpreter with javascript.

[hlipka]

You can also export the whole data set to CSV and parse it with a program. Just enable the 'logging' view and export the 'Logic' source to a file (on each acquisition).

[John Kozell]

Thanks Attila & hlipka. Sorry for the delay in replying.

Yes, hlipka, that's what I ended up doing. The signal I was monitoring has allot of noise, so I was worried about logging too much garbage, and I might have trouble locating the signal.

But I learned that the Logic Analyzer can be triggered, and configured to write a log file only when being triggered - that helped allot. So I was able to trigger, then write the file.

I created a .NET C# Console application to read the file, and used Reactive Extensions to crush the stream into a bursts of 1's & zero's, something like this:

                var acquisition = Samples.ToObservable(NewThreadScheduler.Default)
                    .DistinctUntilChanged(s => s.Value) // Filter out any adjacent high/lows, stream will alternate now.
                    .SkipWhile(s => s.Value != 0) // Make sure the first item is a zero, so we can calculate low durations.
                    .Buffer(2) // Convert single stream into stream of pairs, each having a high then low reading.
                    .Where(p => p.Count > 1) // Make sure entire stream is just pairs, drop the last if it is a singleton.
                    .Select(p => p[1].Time - p[0].Time) // Convert the high/low pairs, into a single measurement of the low duration.
                    .SkipWhile(d => d >= PREAMBLE_LOW_DURATION) // Ignore any pulses before the preamble.
                    .TakeWhile(d => d < PREAMBLE_LOW_DURATION) // Truncate the readings after the next preable.
                    .Select(d => d < _onesThreashold ? SHORT_SYMBOL : LONG_SYMBOL) // Differentiate between long and short pulses, code as 0/1.
                    .Scan((a, b) => a + b) // Concatinate bits into string (bits are reversed, LSB first).
                    .TakeLast(1) // The stream will only have 1 element, take that.
                    .ToArray(); // Convert to simple array. Didn't find a way to just return the first/only element of a stream.

Got a nice output, and created a list of samples that I could analyze. 

Still, I think it would be cool to be able to trigger a script from the Logic Analyzer, can this be done?

-John