Yes, the FFT is a bit “crude”, but I just wanted to get a working version running. The thing with the ending frequency seems like a question of datatype or datatype conversion, but I didn’t really look into it.
I’ve also used the FFT with 1024 points instead of 256 and it runs without issues and is much more precise, but displaying that involves a bit more work, scaling the output to the display window (and I didn’t do that.)
The trigger level presets is all Marco’s work
PS: oh, and I think I fixed the github binary files corruption thing…
Let me take this opportunity and give a big thanks to Pedro, Marco and others that have incrementally contributed to improving the s/w. I think this was the original intend of this product, and gracious individuals have taken upon themselves the task to deliver the s/w. BRAVO!
Yes, Marco and then Pedro did a great job, thank you very much. And the work of Pedro allows each of us to compile the firmware using a free compiler.
The integration of FFT is very nice but I don’t understand what it measures exactly. Look at the following example (230V mains with 10x probe): [attachment=0]IMAG000.jpg[/attachment]
Two things irritate me: [list]
[*]why so many harmonics? The mains should be a very good sine, I don’t expect anything significant above 50Hz. Is this noise because of the limited resolution of the ADC? Or a “feature” of the FFT? Of because of the vertical logarithmic scale?
[*]the rays in the spectrum are not really rays, they are rather blurred - is that a "feature" of the FFT too (e.g. because of the width of the bandpass filter?)