Methods and systems for detecting a position-based attribute of an object using digital codes
View Patent ↗Methods, systems and devices are described for detecting a position-based attribute of a finger, stylus or other object with a touchpad or other sensor having a touch-sensitive region that includes a plurality of electrodes. Modulation signals for one or more electrodes are produced as a function of any number of distinct digital codes. The modulation signals are applied to an associated at least one of the plurality of electrodes to obtain a resultant signal that is electrically affected by the position of the object. The resultant signal is demodulated using the plurality of distinct digital codes to discriminate electrical effects produced by the object. The position-based attribute of the object is then determined with respect to the plurality of electrodes from the electrical effects.
1. A controller for a capacitive position sensor, the controller comprising:
drive circuitry configured to simultaneously transmit a first signal with a first transmitter electrode and a second signal with a second transmitter electrode, wherein the first and second signals are distinct signals based on distinct digital codes; and
receiver circuitry configured to receive resultant signals with a plurality of receiver electrodes proximate to and capacitively coupled with the first transmitter electrode and the second transmitter electrode; wherein the controller is configured to adjust a frequency of the first and second signals based on observed noise in the resultant signals.
2. The controller of claim 1 , wherein the controller is further configured to determine a position-based attribute of the at least one input object proximate a surface of the capacitive position sensor based on the resultant signals.
3. The controller of claim 1 , wherein the drive circuitry is configured to simultaneously transmit a first signal with a first transmitter electrode and a second signal with a second transmitter electrode by one of:
frequency modulating a carrier signal according to the distinct digital codes;
phase modulating a carrier signal according to the distinct digital codes; and
amplitude modulating a carrier signal according to the distinct digital codes.
4. The controller of claim 1 , wherein the distinct digital codes are mathematically independent.
5. The controller of claim 1 , wherein the plurality of distinct digital codes are generated using at least one shift register.
6. The controller of claim 1 , wherein the drive circuitry is further configured to couple a third transmitter electrode with an electrical reference when the drive circuitry simultaneously transmits the first signal with the first transmitter electrode and the second signal with the second transmitter electrode.
7. The controller of claim 1 , wherein the distinct digital codes comprise one of Walsh-Hadamard codes, Gold codes, Kasami Codes, and Barker Codes.
8. The controller of claim 1 , wherein the distinct digital codes comprise Pseudo-Random codes.
9. The controller of claim 1 , wherein the distinct digital codes are multi-level.
10. The controller of claim 9 , wherein the distinct digital codes are binary.
11. The controller of claim 1 , wherein the controller is configured to generate the distinct digital codes by shifting a digital bit sequence.
12. A method of capacitive sensing, the method comprising:
simultaneously transmitting a first signal with a first transmitter electrode and a second signal with a second transmitter electrode, wherein the first and second signals are distinct signals based on distinct digital codes;
receiving resultant signals with a plurality of receiver electrodes proximate to and capacitively coupled with the first transmitter electrode and the second transmitter electrode; and
adjusting a frequency of the first and second signals based on observed noise in the resultant signals.
13. The method of claim 12 , wherein the method further comprises determining a position-based attribute of the at least one input object proximate a surface of the capacitive position sensor based on the resultant signals.
14. The method of claim 12 , wherein the distinct digital codes are binary.
15. The method of claim 12 , wherein the method further comprises generating the distinct digital codes comprises shifting a digital bit sequence.
16. A touch screen comprising,
a plurality of transmitter electrodes;
a plurality of receiver electrodes; and
a controller coupled to the plurality of transmitter electrodes and the plurality of receiver electrodes, the controller configured to:
simultaneously transmit a first signal with a first transmitter electrode of the plurality of transmitter electrodes and a second signal with a second transmitter electrode of the plurality of transmitter electrodes, wherein the first and second signals are distinct signals based on distinct digital codes;
receive resultant signals with a plurality of receiver electrodes proximate to and capacitively coupled with the first transmitter electrode and the second transmitter electrode; and
adjust a frequency of the first and second signals based on observed noise in the resultant signals.
17. The touch screen of claim 16 , wherein the plurality of transmitter electrodes and the plurality of receiver electrodes are disposed on one side of a substrate.
18. The touch screen of claim 16 , wherein the plurality of transmitter electrodes and the plurality of receiver electrodes are disposed on a flexible substrate.
19. The touch screen of claim 16 , wherein the controller is further configured to determine a position-based attribute of the at least one input object proximate a surface of the capacitive position sensor.
20. The touch screen of claim 16 , wherein the distinct digital codes comprise one of Walsh-Hadamard codes, Gold codes, Kasami Codes, and Barker Codes.
21. The touch screen of claim 16 , wherein the distinct digital codes comprise Pseudo-Random codes.
22. The touch screen of claim 20 , wherein the controller further comprises a code generation module configured to generate the distinct digital codes.
23. The touch screen of claim 16 , wherein the controller is configured to simultaneously transmit a first signal with a first transmitter electrode and a second signal with a second transmitter electrode by one of:
frequency modulating a carrier signal according to the distinct digital codes, phase modulating a carrier signal according to the distinct digital codes and amplitude modulating a carrier signal according to the plurality of distinct digital codes.
24. The controller of claim 16 , wherein the distinct digital codes are binary.
25. The controller of claim 16 , wherein the controller is configured to generate the distinct digital codes by shifting a digital bit sequence.