Qtouch describes their method of touch as "charge transfer signal acquisition technology". I have been trying to understand it.
Only working with one single key. I presume Qtouch has the best algorithm from what I have read online, if there is a more robust way that you recommend, please do share.
(I found this, it looks quite sensitive but I dont think it will be as robust as the Qtouch method:
I think there is a fundamental flaw in my understanding.
This is how I think it works:
(refer to the attached pic below)
Step1: Set PB1 and PC1 as outputs, and output a low on both of them to discharge Cs.
Step2: Set PC1 to an input.
Step3: Pulse PB1 high , then put it back to HiZ (or should if remain an output and output a low?)
Step4: Check if PC1 if high.
Step5: Repeat Steps3&4 until PC1 measures a High.
Step6: If the number of iterations taken is below the threshold then it is said to be touched.
In Step2: Should PC1 be an input or set set to output low?
In Step3 is PB1 is pulsed between high/low or High/HiZ?
I dont understand how the process works. To me what would make sense is if you remove PC1 all together, and ground the side of Cs that used to connect to PC1. Now the voltage built up across Cs is with respect to GND. And when you pulse PB1, Cs will charge up with each pulse, and can be measured on PB1 (PB1 Switching between an output and an input).
But clearly my reasoning is wrong because that is not how it is done. I am starting to think my cap knowledge that has served me quite well so far is fundamentally flawed.
I look at Cs as a cap with one leg connected to CB1, and the other leg connected to nothing (CS1 is a HiZ input I presume), so how can it ever build up a voltage across it?
Thank you for any help, your insight and time is much appreciated!