Am Montag, 17. April 2023, 14:37:16 CEST schrieb Ondřej Jirman: > Hello Heiko, > > On Mon, Apr 17, 2023 at 10:34:20AM +0200, Heiko Stübner wrote: > > Hi Peter, Ondrej, > > > > Am Mittwoch, 5. April 2023, 15:53:39 CEST schrieb Ondřej Jirman: > > > [...] > > > > > > (I have to press quite hard to get bellow 300 and to get reliable detection > > > of volume down key press) > > > > > > On development version of the phone, the value returned by sardac is less > > > variable. Basically either 298.828125 or 300.5859375 but it's also on > > > the edge. > > > > > > I suggest raising the threshold to something like 600 and to do your own > > > testing, to get more data points. Unpressed value is ~1791.2109375 on both > > > phones, so 400 still gets a lot of headroom. And volume up is always < 15 > > > in my tests. > > > > did this get more attention meanwhile? > > > > I don't have a Pinephone Pro myself, so you'll need to decide between you > > about the value and the concern Ondrej raised here for the value. > > It's safe and needed to use a higher value. so in a nutshell, if I change "Volume Down" to say 400000 instead of the current 300000, the patch is good to go? I.e. that was my main question :-), as you raised the objection to the value in your initial reply Thanks Heiko > SAR ADC input is pulled high to 1.8V unless some key is pressed, so unpressed > value will always be around 1800 on all Pinephones, and pressed value will > depend on contact quality and tolerances. For volume down, SAR ADC input is fed > from a resistor divider of (10kOhm + 2kOhm) from 1.8V power rail. So that gives > 2/12*1.8 = 0.3V. We can't have the press detection threshold right at this > voltage, because: > > 1) these resistors have tolerances that will randomly result in measured voltage > being above or below the 0.3V on real devices (-1% on 10k and +1% on 2k = > 2*1.01/(10*0.99+2*1.01)*1.8 = 305 mV - already too high even without > considering switch contact quality), and > > 2) those piddly membrane switches apparently have their own random resistance > that is added to the bottom leg of the resistor divider, and depends on > strenght of the press on some devices (and switches may develop higher > resistance with age/use). > > Schematic: https://megous.com/dl/tmp/1125d9248a8213b3.png > > kind regards, > o. > > > Thanks > > Heiko >
