Input device transmitter path error diagnosis

• US 8,692,794 B2
• Filed: 01/25/2011
• Issued: 04/08/2014
• Est. Priority Date: 01/25/2011
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Fang, Wen
• Primary Examiner(s): Cheng, Joe H
• Assistant Examiner(s): Xie, Kwin
• Application Number:
  US13/012,943
• Publication Number:
  US 20120188195A1
• Time in Patent Office: 1,169 Days
• Field of Search: None
• US Class Current: 345/174
• CPC Class Codes: G01R 31/2832 Specific tests of electronic circuits not provided for elsewhere G01R31/2801, G01R31/316 take precedence
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

A processing system configured for capacitive sensing comprises transmitter circuitry, a first internal diagnostic mechanism, and a determination module. The transmitter circuitry is configured to transmit during a first time period with a first transmitter path of a plurality of transmitter paths in an input device. Each transmitter path of the plurality of transmitter paths is configured for capacitive sensing. The first internal diagnostic mechanism comprises a selectable leakage path. The selectable leakage path is configured to be coupled with the transmitter circuitry. The determination module is configured to determine if a discontinuity exists within the first transmitter path based on a discharge rate for the first transmitter path. The discharge rate is acquired during a second time period via the selectable leakage path of the first internal diagnostic mechanism, wherein the second time period occurs after the first time period.

Claims

1. A processing system configured for capacitive sensing, said processing system comprising:

transmitter circuitry configured to transmit during a first time period with a first transmitter path of a plurality of transmitter paths in an input device, wherein each transmitter path of said plurality of transmitter paths is configured for capacitive sensing;

a first internal diagnostic mechanism comprising;

a selectable leakage path,

a buffered output coupled with said selectable leakage path and said first transmitter path, and

a selectable diagnostic node coupled as an input select of said selectable leakage path, wherein said selectable leakage path is configured to be coupled with said transmitter circuitry to intentionally discharge a charged portion of said transmitter circuitry with which said selectable leakage path is coupled; and

a determination module configured to determine when a discontinuity exists within said first transmitter path based on a discharge rate for said first transmitter path, wherein said discharge rate is acquired during a second time period via said selectable leakage path of said first internal diagnostic mechanism, wherein said second time period occurs after said first time period.

2. The processing system of claim 1, wherein said selectable leakage path comprises:

a first selection mechanism coupled with an enable input of said transmitter circuitry and configured for disabling said selectable leakage path when said transmitter circuitry is enabled for transmitting and enabling said selectable leakage path when said transmitter circuitry is not enabled for transmitting; and

a second selection mechanism coupled in series with said first selection mechanism and configured for addressably enabling said selectable leakage path.

3. The processing system of claim 1, wherein said selectable leakage path comprises:

one of a selectable weak pull-down transistor and a current source.

4. The processing system of claim 1, wherein said transmitter circuitry is further configured to:

transmit a first transmitter signal with said first transmitter path during a third time period; and

said determination module is further configured to determine when said first transmitter path is ohmically coupled to a second transmitter path of said plurality of transmitter paths based upon a first resulting signal at an output of a second internal diagnostic mechanism coupled with said second transmitter path, wherein said first resulting signal is acquired via said output of said second internal diagnostic mechanism while said transmitter circuitry transmits said first transmitter signal with said first transmitter path.

5. The processing system of claim 4, wherein said determination module is further configured to determine when said first transmitter path is ohmically coupled to a third transmitter path of said plurality of transmitter paths based on a second resulting signal at an output of a third internal diagnostic mechanism coupled with said third transmitter path, wherein said second resulting signal is acquired via said output of said third internal diagnostic mechanism while said transmitter circuitry transmits said first transmitter signal with said first transmitter path.

6. The processing system of claim 4, wherein said transmitter circuitry is further configured to transmit a second transmitter signal on said second transmitter path during said third time period, wherein said second transmitter signal is of opposite polarity to said first transmitter signal.

7. The processing system of claim 4, wherein said transmitter circuitry is further configured to:

transmit a second transmitter signal during a fourth time period with said first transmitter path;

said first internal diagnostic mechanism is further configured to enable an output of said first internal diagnostic mechanism; and

said determination module is further configured to determine when said first transmitter path is ohmically coupled to a reference potential based on a measurement of a second resulting signal, wherein said second resulting signal is acquired via said output of said first internal diagnostic mechanism while said transmitter circuitry transmits said second transmitter signal with said second transmitter path.

8. The processing system of claim 1, wherein said determination module is further configured to determine when said first transmitter path is ohmically coupled to at least one receiver path of a capacitive sensing device based on a comparison of a measurement of capacitive loading of said first transmitter path to a predetermined capacitive loading threshold value.

9. The processing system of claim 1, wherein said determination module is further configured to determine when said discontinuity exists based on a comparison of a measurement of capacitance of said first transmitter path to a predetermined transmitter path capacitance threshold value, wherein said measurement of capacitance is acquired via said selectable leakage path and wherein said measurement of capacitance is based on said discharge rate for said first transmitter path.

10. A capacitive sensing device comprising:

a plurality of transmitter paths, wherein each transmitter path of the plurality of transmitter paths is configured to for capacitive sensing; and

a processing system coupled with said plurality of transmitter paths, said processing system configured to;

transmit during a first time period with a first transmitter path of said plurality of transmitter paths;

enable a selectable leakage path of a first internal diagnostic mechanism of said processing system during a second time period, said first internal diagnostic mechanism comprising said selectable leakage path, a buffered output coupled with said selectable leakage path and said first transmitter path, and a selectable diagnostic node coupled as an input select of said selectable leakage path, wherein responsive to enablement said selectable leakage path is configured to be coupled with said first transmitter path to intentionally discharge a charge accumulated on said first transmitter path; and

determine when a discontinuity exists within said first transmitter path based on a discharge rate for said first transmitter path, wherein said discharge rate is acquired during a second time period via said selectable leakage path of said first internal diagnostic mechanism, and wherein said second time period occurs after said first time period.

11. The capacitive sensing device of claim 10, wherein said processing system is further configured to:

transmit a first transmitter signal with said first transmitter path during a third time period; and

determine when said first transmitter path is ohmically coupled to a second transmitter path of said plurality of transmitter paths based upon a first resulting signal at an output of a second internal diagnostic mechanism coupled to said second transmitter path, wherein said first resulting signal is acquired via said output of said second internal diagnostic mechanism while said processing system is transmitting said first transmitter signal with said first transmitter path.

12. The capacitive sensing device of claim 11, wherein said processing system is further configured to:

determine when said first transmitter path is ohmically coupled to a third transmitter path of the plurality of transmitter paths based on a second resulting signal received at an output of a third internal diagnostic mechanism coupled with said third transmitter path, wherein said second resulting signal is acquired via said output of said third internal diagnostic mechanism and while said processing system is transmitting said first transmitter signal during said third time period with said first transmitter path.

13. The capacitive sensing device of claim 10, wherein said processing system is further configured to determine when said first transmitter path is ohmically coupled to at least one receiver path of said capacitive sensing device based on a comparison of a measurement of capacitive loading of said first transmitter path to a predetermined capacitive loading threshold value.

14. The capacitive sensing device of claim 10, wherein said processing system is further configured to determine when said discontinuity exists based on a comparison of a measurement of capacitance of said first transmitter path to a predetermined transmitter path capacitance threshold value, wherein in said measurement of capacitance is acquired via said selectable leakage path, and wherein said measurement of capacitance is based on said discharge rate for said first transmitter path.

15. A method of input device transmitter path error diagnosis, said method comprising:

transmitting during a first time period with a first transmitter path of a plurality of transmitter paths in an input device, wherein each transmitter path of said plurality of transmitter paths is configured for capacitive sensing;

enabling a selectable leakage path of an internal diagnostic mechanism of a processing system during a second time period, said internal diagnostic mechanism comprising said selectable leakage path, a buffered output coupled with said selectable leakage path and said first transmitter path, and a selectable diagnostic node coupled as an input select of said selectable leakage path, wherein responsive to enablement said selectable leakage path is configured to intentionally discharge a charge accumulated on said first transmitter path; and

determining when a discontinuity exists within said first transmitter path based on a discharge rate for said first transmitter path, wherein said discharge rate is acquired during a second time period via said selectable leakage path of said internal diagnostic mechanism of said processing system of said input device, wherein said second time period occurs after said first time period.

16. The method as recited in claim 15, further comprising:

transmitting a first transmitter signal with said first transmitter path during a third time period; and

determining when said first transmitter path is ohmically coupled to a second transmitter path of said plurality of transmitter paths based upon a first resulting signal at an output of a second internal diagnostic mechanism coupled to said second transmitter path, wherein said first resulting signal is acquired via said output of said second internal diagnostic mechanism while transmitting said first transmitter signal with said first transmitter path.

17. The method as recited in claim 16, further comprising:

determining when said first transmitter path is ohmically coupled to a third transmitter path of said plurality of transmitter paths based on a second resulting signal received at an output of a third internal diagnostic mechanism coupled with said third transmitter path, wherein said second resulting signal is acquired via said output of said third internal diagnostic mechanism while transmitting said first transmitter signal with said first transmitter path.

18. The method as recited in claim 15, further comprising:

determining when said first transmitter path is ohmically coupled to a receiver path based on a comparison of a measurement of capacitive loading of said first transmitter path to a predetermined capacitive loading threshold value.

19. The method as recited in claim 15, further comprising:

determining when said discontinuity exists based on a comparison of a measurement of capacitance of said first transmitter path to a predetermined transmitter path capacitance threshold value, wherein in said measurement of capacitance is acquired via said selectable leakage path, and wherein said measurement of capacitance is based on said discharge rate for said first transmitter path.