Hover touch using Trill Square

joellee

Hi! I was wondering if anyone has used the trill square for hover touch before? It seems that in centroid mode, it only takes discrete touches that make contact with the square. I've switched to using DIFF mode and taking raw readings, but that doesn't seem to be very reliable either (mostly noise).

I saw that proximity sensing is possible, and works well through other mediums like glass and plasic, but not through air? Would appreciate if anyone has clarity into whether hover touch is possible, or if this is a fruitless pursuit.

Thanks 😃 !

giuliomoro

You should try in raw mode to set a small prescaler value and large bit size. Do you see enough "proximity effect" that way?

joellee

That seems to have worked better! I'll still have to do some tuning for the parameters as there's a lot of noise with a low prescaler. Do you have any suggestions on how to filter the raw capacitance sensor readings?

To add some context to the intention behind implementing hover touch, I essentially want to use the trill square to hover and then also to touch as an indication of a click. Basically, do what trill square does in centroid mode but with hovering instead of physically touching the board.

giuliomoro

If you find a good prescaler/bit depth combination that in RAW mode allows you to see enough range on the pads, the next step is to do this:

set prescaler
set bit depth
update baseline
use DIFF mode: if it looks like you have enough signal-to-noise-ratio to distinguish the touches, set it to CENTROID mode
if you don't get touches, try reducing the minimum touch size till they start appearing

As for filtering, it depends on the type of noise that you are seeing.

joellee

Hi giuliomoro,

Sorry for the late reply, I'll certainly give that a shot and get back to you.

joellee

I've tried with the follow settings:

trill.setMode(Trill::RAW);
trill.setPrescaler(1);
trill.setScanSettings(1, 16);

#if DIFF_MODE
trill.updateBaseLine();
#endif

Somehow, I'm back to getting no readings... Also, I'm not noticing a very obvious difference in the readings when changing the prescaler.

This is how the readings look right now. Before I had readings that were noisy (giving me some values) but not flattened to 0 like the above screenshot.

giuliomoro

If it's RAW it should provide non-zero readings on all pads all the time with such a small prescaler. I see you have a DIFF_MODE define, does it mean you are setting DIFF somewhere not shown? The prescaler should change the RAW readings when no touch: lower prescaler -> higher readings. If you clip