ESP32S2: TouchIO default threshold is unsatisfactory

[hierophect]

Running the following on a Saola 1 Wrover board:

import time
import board
import touchio

touch_IO1 = touchio.TouchIn(board.IO1)
touch_IO2 = touchio.TouchIn(board.IO2)

while True:
    if touch_IO.value:
        print("Touched IO1!")
    if touch_IO.value:
        print("Touched IO2!")
    time.sleep(0.05)

will result in A1 constantly reading as touched. If additional pins are added (IO3, IO4, etc) then all pins before the last one created will constantly trigger.

@ladyada ping so this is on your radar. I'm investigating now.

[microdev1]

Unable to replicate this. Tested with :-

Adafruit CircuitPython 6.2.0-beta.2-230-g64192b0eb on 2021-03-02; microS2 with ESP32S2

I suspect interference problems. Can you try with pins which are physically apart from each other.

[hierophect]

@microdev1 interesting. I've edited the post to include the board (Saola Wrover). Your guess was correct, the pins only interfere when they're adjacent, putting them one or more pins away (IO1 and IO3) stops the issue. Should we consider tweaking the threshold value, or breaking it out on the board level? When a wire is connected to the pin, it's so sensitive that even just holding your hand within an inch the wire causes it to go off.

[hierophect]

Nevermind, I see it's in the API. Sorry, haven't worked with TouchIO before. Still, I do wonder if it's worth adjusting the threshold from the board level since this could be a confusing issue for a new user.

[microdev1]

Ya... while implementing TouchIO... I did all the testing on my microS2 which has very small traces + it is 4 layers thus having different electrical characteristics then most other boards. I think we can settle on a middle ground for threshold values which works for all of the boards... the api also offers some filtering features which might be helpful.

[jepler]

I notice that the docs state

When the TouchIn object is created, an initial raw_value is read from the pin, and then threshold is set to be 100 + that value.

I doubt that all ports do exactly this, so the docs may need to be updated, but basically I think that for other platforms we've found that adding a constant to a value that is assumed to be the 'background value' was an effective but simple way to set the initial threshold.