Method and apparatus for testing projected capacitance matrices and determining the location and types of faults

1. A method comprising:

measuring a capacitance value of a sensor;

comparing the measured capacitance values to a first reference value;

adjusting a calibration parameter in response to comparing the measured capacitance value to the first reference value; and

determining sensor integrity by comparing the value of the adjusted calibration parameter to one or more second reference values, wherein determining sensor integrity comprises identifying at least one of a plurality of fault conditions, and wherein each of the plurality of fault conditions is defined by at least one of the one or more second reference values.

2. The method of claim 1 wherein the sensor is a mutual capacitance sensor.

3. The method of claim 1 , wherein measuring the capacitance value of the sensor comprises generating a current from the sensor.

4. The method of claim 3 , wherein the calibration parameter is a setting for a programmable current source coupled to a circuit configured to perform measuring the capacitance value of the sensor.

5. The method of claim 1 wherein the plurality of fault conditions comprises a short between a first electrode and a second electrode.

6. The method of claim 5 wherein the first electrode receives a drive signal and the second electrode is coupled to a voltage potential.

7. The method of claim 6 wherein the voltage potential is ground.

8. The method of claim 5 herein the first electrode receives a drive signal and the second electrode is a shield layer coupled to a voltage potential.

9. The method of claim 8 , wherein the voltage potential is ground.

10. The method of claim 5 , wherein the first electrode receives a drive signal and the second electrode is configured to receive the drive signal from the first electrode and output a current.

11. The method of claim 1 wherein the plurality of fault conditions comprises a poor connection on either a first drive electrode or a second receive electrode.

12. The method of claim 1 , wherein the plurality of fault conditions comprises a poor connection between the sensor and a circuit configured to measure capacitance.

13. An apparatus comprising:

means for measuring a capacitance value of a sensor;

means for comparing the measured capacitance values to a first reference value;

means for adjusting a calibration parameter in response to comparing the measured capacitance value to the first reference value; and

means for determining sensor integrity by comparing the value of the adjusted calibration parameter to one or more second reference values, wherein the means for determining sensor integrity identifies at least one of a plurality of fault conditions, and wherein each of the plurality of fault conditions is defined by at least one of the one or more second reference values.

14. The apparatus of claim 13 wherein the means for measuring the capacitance value comprises a capacitance-to-current conversion circuit.

15. The apparatus of claim 14 wherein the means for adjusting the calibration parameter comprises a programmable current source coupled to an output of the capacitance to current conversion circuit.

16. A system comprising:

a capacitance sensor;

a capacitance measurement circuit coupled with the capacitance sensor, the capacitance measurement circuit configured to measure a capacitance value of the capacitance sensor;

a calibration circuit coupled with the capacitance measurement circuit, the calibration circuit configured to adjust a calibration parameter based on the measured capacitance value and a first reference value; and

a controller coupled with the capacitance measurement circuit and the calibration circuit and configured to compare the value of the adjusted calibration parameter to one or more second reference values in order to identify faults and fault types in the capacitance sensor, wherein the one or more second reference values define the faults and the fault types.

17. The system of claim 16 wherein the capacitance measurement circuit is a capacitance to current converter.

18. The system of claim 17 wherein the calibration circuit is a programmable current source coupled to the capacitance to current converter.

19. The system of claim 16 , wherein the controller is coupled to the capacitance sensor through a bed of nails tester.

20. The system of claim 16 , wherein the controller is coupled to the capacitance sensor through a printed circuit board.

21. The system of claim 16 , wherein the controller is coupled to the capacitance sensor through direct bonding to a touch panel substrate.