Arduino in Test Instrumentation - Part 1: SCPI Lib

My 32KB 4Duino (Leonardo equivalent) kept grinding to a halt.  The issue is that when you ask the framework if there are any errors, it pops one off the stack if it exists OR it creates a new empty one and returns that.  These are all allocated in dynamic memory and that empty one is never deallocated.  Problem being that to determine if an error occurred you have to ask and you always get one!  The solution is to either (a) deallocate the memory for that empty error in your own code; or (b) change the framework to manage errors a bit better.  Given it’s not being maintained, then (b) is not a totally unsuitable approach.  Strange actually, because it properly manages the SCPI tokens it creates, just not the error tokens.  I don’t know if the Vrekrer implementation has fixed this - did it not use this one as a base or was that yet another library??? I forget, as you say there’s a few out there now.

That's an interesting idea. I'll have a look at that.

I hadn't considered the error status return at all, but I'm sure it can be wangled somehow.

I'm getting a little bit confused with all this [there are too many Jans in the world, aren't there!].

I need it to be lightweight to run on an UNO, so you're saying that rules out the Breuer one [which, from my cursory glance at the git page, does look like it's done reasonably well].

I was curious about the Vrecker one, mainly because it appears in the Library Manager so it's very easy to use in an Arduino project.

It sounds like I should stick with the original one. How did you find the memory leak? Did you do that with the Arduino IDE somehow, or were you using a different processor and other tools?

You could use the error handler for that purpose, maybe: If the parser detects an error, throw it over the wall to the meter?

And whatever the meter sends back, relay to the host?

In general, it would work.

You'd have to refine the error querying. Because you will have to be able to report error status on any of the two instruments when SYST:ERR queries are fired.

You will want something to do that in that case Jon.  The library Jan and I have used here works, but it does have a memory leak in the error handling code (easily fixed) and I found it necessary to write a fair bit of processing code with it.  It’s not maintained but I don’t think that’s an issue as it’s pretty simple and quick to get going.  The library you point out didn’t convince me that much so I haven’t tried it.  The Jan Breuer library scpi-parser looks very complete but may be too big for an Arduino depending upon the rest of the sketch.  The examples are enough to get you going but, not being a C/C++ programmer of any experience, I’ve had to trawl through the code to work out what I need to do as it isn’t well commented and the documentation, although much better than most libraries out there, is still a bit lightweight and possibly not up to date.

For something simple, I’d go with the one discussed originally by Jan.  I may well swap back to it.  I also could provide a more comprehensive working example for you as well if you need it.