System and method for diagnostics of a grid based digitizer

1. A method for testing a capacitive based digitizer to determine a defect in electrical connectivity of the digitizer, wherein the digitizer includes a sensor grid formed from a first set of parallel conductive elements and a second set of parallel conductive elements patterned on one or more layers of a substrate, wherein the second set is patterned orthogonally from the first set to form the sensor grid and wherein all the conductive elements from both the first and the second set are patterned on the substrate and electrically insulated from each other, the method comprising:

providing an input signal on one or more first conductive elements of the sensor grid;

detecting output signals in a plurality of second conductive elements of the sensor grid responsive to the input signal in the at least one first conductive element, the plurality of second conductive elements being other than the one or more first conductive elements;

determining a defect in electrical connectivity in the sensor grid based on the output signals, wherein at least the providing, detecting and determining is performed autonomously by the digitizer; and

identifying a conductive element of the sensor grid with the defect in electrical connectivity based on the output signals.

2. The method according to claim 1 , wherein the method for testing a digitizer to determine a defect in electrical connectivity of the digitizer is performed in the absence of user interaction with the digitizer.

3. The method according to claim 1 wherein the method is performed by firmware of the digitizer.

4. The method according to claim 1 , wherein the output signals are detected from conductive elements positioned orthogonally to the one or more first conductive elements on which the input signal is provided.

5. The method according to claim 1 , wherein the output signals are detected from conductive elements parallel to the one or more first conductive elements on which the input signal is provided.

6. The method according to claim 1 , wherein the output signals are effected by capacitive coupling between the one or more first conductive elements and the plurality of second conductive elements of the sensor grid.

7. The method according to claim 1 wherein the output signals are effected by capacitive coupling at grid junctions formed between the first and second set of parallel conductive elements.

8. The method according to claim 1 , wherein pairs of parallel conductive elements are input to differential amplifiers and wherein output from the differential amplifiers is sampled to produce the output signals from the sensor grid.

9. The method according to claim 8 comprising grounding a first input of a differential amplifier to detect a signal propagating on a second input of the differential amplifier.

10. The method according to claim 1 , comprising:

providing an input signal on the first set of parallel conductive elements; and

detecting output signals from the second set of parallel conductive elements.

11. The method according to claim 1 wherein the input signal is an AC signal.

12. The method according to claim 11 , wherein the input signal is provided at a frequency used during user interaction with the digitizer for finger detection.

13. The method according to claim 1 , wherein detecting includes comparing the amplitude of the output signals from the sensor grid to a pre-defined threshold.

14. The method according to claim 1 , wherein detecting includes comparing the energy of the output signals from the sensor grid in a pre-defined frequency band to a pre-defined threshold.

15. The method according to claim 1 , wherein detecting includes comparing the output signals of the sensor grid to properties of the input signal.

16. The method according to claim 1 , comprising comparing amplitude of each of the output signals to an average amplitude of the output signals.

17. The method according to claim 16 , comprising comparing the amplitude of each of the output signals to a standard deviation of the average amplitude of the output signals.

18. The method according to claim 1 , comprising determining connectivity between conductive elements of the sensor grid and circuitry of the digitizer.

19. The method according to claim 1 , comprising detecting an electrical break in conductive elements of the sensor grid.

20. The method according to claim 19 comprising:

providing an AC input signal on a first end of a first conductive element of the sensor grid, the first conductive element including a first end and a second end;

sampling an output signal from at least one second conductive element crossing the first conductive element closest to the second end;

comparing the output signal to a threshold; and

determining that the first conductive element includes the electrical break responsive to the output signal being below the threshold.

21. The method of claim 19 , comprising determining a location of the electrical break along the defected conductive element.

22. The method according to claim 1 , comprising determining cross-talk between gridlines of the sensor grid.

23. The method according to claim 22 comprising:

providing an AC input signal on the one first conductive element of the sensor grid;

sampling an output signal from a neighboring conductive element that is parallel to the one first conductive element;

comparing the output signal to a threshold; and

determining that there is cross talk between the one first conductive element on which an input signal is provided and the neighboring conductive element responsive to the output signals sampled being above the threshold.

24. The method according to claim 1 , comprising determining shorts between gridlines of the sensor grid.

25. The method according to claim 24 comprising:

providing an AC input signal on one first conductive element of the sensor grid;

sampling output signals from neighboring conductive elements that are parallel to the one first conductive element;

comparing the output signals to a threshold; and

determining that there is a short between the one first conductive element through which an input signal is transmitted and the neighboring conductive element responsive to an output signal from the neighboring conductive element being above the threshold.

26. The method according to claim 1 , comprising determining an imbalance between gridlines of the sensor grid.

27. The method according claim 26 comprising:

providing an AC input signal on one first conductive element of the sensor grid;

sampling an output signal from at least one differential amplifier having input from two parallel conductive elements crossing the one first conductive element;

comparing the output signal to a threshold; and

determining that there is an imbalance between the two parallel conductive element serving as input to the differential amplifier responsive to the output signal being above the threshold.

28. The method according to claim 1 , comprising reporting the determined defect to a host computer associated with the digitizer.

29. The method according claim 28 comprising reporting the determined defect to a user interacting with the host computer.

30. The method according to claim 28 comprising determining if the sensor grid is operable and reporting operability of the sensor grid.

31. The method according to claim 1 comprising compensating for at least one malfunctioning property of the digitizer.

32. The method of claim 1 , wherein the conductive elements in each of the first and second set of parallel conductive elements are gridlines.

33. The method of claim 1 , wherein the defect in electrical connectivity detected includes a break along the conductive element of the sensor grid and at least one of a short between two conductive elements of the sensor grid and cross talk between conductive elements of the sensor grid.

34. The method of claim 1 , wherein the conductive element of the sensor grid that is identified with the defect in electrical connectivity is one of the one or more first conductive elements or one of the plurality of second conductive elements.