Methods for two-touch detection with resistive touch sensor and related apparatuses and systems

1. A method for a five-wire resistive touch sensor comprising a first conductive layer, a first layer electrode, a second conductive layer, and four second layer electrodes, the method comprising:

generating a first voltage gradient in a first direction across the second conductive layer;

while the first voltage gradient is active, measuring a first voltage of the second layer electrode and a first current across the touch sensor;

generating a second voltage gradient in a second direction across the second conductive layer;

while the second voltage gradient is active, measuring a second voltage of the second layer electrode and a second current across the touch sensor;

comparing each of the first and second currents to a respective threshold; and

detecting a two-touch event as a function of said comparing.

2. The method of claim 1 , wherein the four second layer electrodes are positioned at or proximate four corners of the second conductive layer respectively.

3. The method of claim 1 , wherein the first direction is substantially orthogonal to the second direction.

4. The method of claim 1 , wherein said detecting a two-touch event comprises detecting that at least one of the first and second currents exceeds the respective threshold.

5. The method of claim 1 , further comprising determining first and second touch contact positions of the two-touch event.

6. The method of claim 5 , wherein determining the first and second touch contact positions comprises:

estimating a first spacing of the first and second touch contact positions in a first dimension corresponding to the first direction as a function of the first current;

estimating a second spacing of the first and second touch contact positions in a second dimension corresponding to the second direction as a function of the second current; and

estimating two ordinates for the first dimension as a function of the first spacing and the first measured voltage, and estimating two ordinates for the second dimension as a function of the second spacing and the second measured voltage.

7. The method of claim 6 , further comprising refining the estimated ordinates.

8. The method of claim 7 , further comprising measuring a contact resistance between the first conductive layer and the second conductive layer.

9. The method of claim 8 , wherein refining the estimated ordinates further comprises compensating the estimated ordinates for the first dimension and the estimated ordinates for the second dimension as a function of the measured contact resistance.

10. The method of claim 9 , wherein measuring the contact resistance comprises measuring a resistance between the first layer electrode and, collectively, the four second layer electrodes.

11. The method of claim 9 , further comprising measuring, for each said second layer electrode, a respective individual resistance between the second layer electrode and the first layer electrode.

12. The method of claim 11 , wherein refining the estimated ordinates further comprises, compensating the measured contact resistance as a function of the measured individual resistances between the four second layer electrodes and the first layer electrode prior to the estimated ordinates as a function of the measured contact resistance.

13. The method of claim 6 , further comprising pairing the estimated ordinates for the first dimension and the estimated ordinates for the second dimension to provide first and second contact position coordinates.

14. The method of claim 13 , further comprising:

generating first corner-to-corner voltage gradient in the second conductive layer and measuring a first corner-to-corner current; and

generating second corner-to-corner voltage gradient in the second conductive layer and measuring a second corner-to-corner current, wherein the pairing of the estimated ordinates is based in part on a comparison of the first and second corner-to-corner currents.

15. A controller apparatus for a five-wire touch sensor comprising a first conductive layer, a first layer electrode, a second conductive layer, four second layer electrodes, the controller apparatus comprising:

a processor;

voltage drive circuitry for driving each of the four second layer electrodes and the first layer electrode;

detector circuitry for detecting voltage or current output of each of at least three of the second layer electrodes and the first layer electrode; and

memory operably coupled to the processor and having processor-executable instructions stored thereon that, when executed, cause the processor to implement the method of claim 1 .

16. The controller apparatus of claim 15 , wherein the detector circuitry comprises, for each of at least one of the first layer electrode or second layer electrodes, a respective Analog to Digital Converter (ADC).

17. The controller apparatus of claim 16 , wherein the detector circuitry further comprises, for each of at least one of the first layer electrode or second layer electrodes, a respective offset circuit that amplifies a difference between a baseline voltage and the voltage output of a corresponding electrode.

18. The controller apparatus of claim 17 , wherein each said offset circuit comprises a respective Digital to Analog Converter that outputs the baseline voltage, and a respective amplifier that amplifies the difference between the baseline voltage and the voltage output of the corresponding electrode, the difference being input to a corresponding ADC.

19. A touch sensor system comprising:

a five-wire resistive touch sensor; and

the controller apparatus of claim 18 .