Touchscreen Sensitivity Questions

[Munque]

I'm working with this Touch screen - 3.7" and it seems to be insensitive. It works if you push hard enough, but that makes it sort of impractical to use. I was assuming a solution might be on the last line of the following code...

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#include "TouchScreen.h"
#define Yp A4 // must be an analog pin, use "An" notation!
#define Xn A5 // must be an analog pin, use "An" notation!
#define Yn 14 // can be a digital pin
#define Xp 27 // can be a digital pin
TouchScreen ts = TouchScreen(Xp, Yp, Xn, Yn, 300);

My assumption was the 300 related to sensitivity, but so far no changes to that number have any effect.

Second possibility was here...

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void loop() {
	TSPoint p = ts.getPoint();
	if (p.z > ts.pressureThreshhold) {
		//Do something.
	}
}

I attempted to diminish the threshold as follows...

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void loop() {
	TSPoint p = ts.getPoint();
	if (p.z != 0) {
		//Do something.
	}
}

So far the device remains stubbornly insensitive.
I'm trying to determine if it's there's a coding solution or we're just confronting a limitation of the touchscreen device itself.

[mikeysklar]

Did you try using a multimeter to measure the resistance between X+ and X-? Our example assumes a 300 ohm resistance, but your display might have a different value.

// For better pressure precision, we need to know the resistance
// between X+ and X- Use any multimeter to read it
// For the one we're using, its 300 ohms across the X plate
TouchScreen ts = TouchScreen(XP, YP, XM, YM, 300);

https://github.com/adafruit/Adafruit_To ... endemo.ino

Did you experiment further with the MINPRESSURE readings?

// we have some minimum pressure we consider 'valid'
// pressure of 0 means no pressing!
if (p.z > MINPRESSURE && p.z < MAXPRESSURE) {
Serial.print("X = "); Serial.print(p.x);
Serial.print("\tY = "); Serial.print(p.y);
Serial.print("\tPressure = "); Serial.println(p.z);

https://github.com/adafruit/Adafruit_To ... shield.ino

[Munque]

Did you try using a multimeter to measure the resistance between X+ and X-?

Yes 650Ω, but setting

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TouchScreen ts = TouchScreen(Xp, Yp, Xn, Yn, 650);[code] had no affect.  I tried a range of numbers, from 100 to 2000 and never experienced a difference in performance.

[quote="mikeysklar"]Did you experiment further with the MINPRESSURE readings?[/quote]
Rather than play with settings I just monitor them in the Arduino Serial Monitor where they generally range from 0 to -500, never positive, but they sometimes spike between -2000 & -4000 and occasionally -8000
It is never possible to get a response at all until putting a significant amount of pressure -- far more pressure (easily 10X the pressure) you'd put on an iPhone.