Systems and methods for capacitive touch detection

• US 9,939,969 B2
• Filed: 05/08/2015
• Issued: 04/10/2018
• Est. Priority Date: 05/09/2014
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Yuan, Hangjian, Zhou, Hao, Xie, Bike, Gao, Kanke, Shen, Xudong
• Primary Examiner(s): Boddie, William
• Assistant Examiner(s): Gyawali, Bipin
• Application Number:
  US14/707,694
• Publication Number:
  US 20150324035A1
• Time in Patent Office: 1,068 Days
• Field of Search: None
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

System and methods are provided for touch detection. An example system includes: a measurement unit configured to acquire capacitance measurement data from a touch panel; a pre-processing unit configured to detect whether a touch event occurs on the touch panel based at least in part on the capacitance measurement data and generate an activation signal in response to the detection of the touch event; and a microcontroller unit configured to be activated in response to the activation signal to perform post-processing operations related to the touch event.

Claims

1. A system for touch detection, the system comprising:

a measurement unit configured to acquire capacitance measurement data from a touch panel;

a pre-processing unit configured to detect whether a touch event occurs on the touch panel based at least in part on the capacitance measurement data and generate an interrupt signal to a microcontroller unit in response to the detection of the touch event; and

the microcontroller unit configured (i) to be in a reduced-power state prior to receiving the interrupt signal and (ii) to be activated by the interrupt signal to exit the reduced-power state in order to perform post-processing operations related to the touch event;

wherein detecting of whether the touch event occurs includes;

adjusting a baseline value B by an amount (C−

B)*F, wherein C represents a capacitance measurement, and F is a predetermined factor,

generating a threshold signal value T as equal to B times a predetermined value,

generating a difference D as equal to C−

B, and

determining whether a touch event has occurred based on a comparison between D and T;

wherein the measurement unit is further configured to;

acquire self capacitance measurement data from the touch panel by switching to a configuration in which a first capacitor and a first resistor are connected in parallel from an inverting input of an amplifier to an output of the amplifier, and a second resistor is connected from a second capacitor to the inverting input, and

acquire mutual capacitance by switching to a configuration in which the first capacitor and the second capacitor and a third resistor are connected in parallel from the inverting input to the output.

2. The system of claim 1, wherein the pre-processing unit includes:

a raw-data processor configured to generate a differential signal based at least in part on the capacitance measurement data and a baseline signal; and

a touch detector configured to determine whether the touch event occurs on the touch panel based at least in part on the differential signal.

3. The system of claim 2, wherein the pre-processing unit further includes:

a baseline-tracking unit configured to update the baseline signal based at least in part on the differential signal.

4. The system of claim 3, wherein the baseline-tracking unit is configured to be deactivated in response to the touch event being detected.

5. The system of claim 2, wherein the touch detector includes:

a multiplication component configured to generate a threshold signal based at least in part on a predetermined threshold and the baseline signal; and

a comparator configured to compare the differential signal and the threshold signal to determine whether the touch event occurs on the touch panel.

6. The system of claim 5, wherein the comparator is further configured to generate the interrupt signal in response to the differential signal being larger in magnitude than the threshold signal.

7. The system of claim 2, further comprising:

a baseline memory configured to store data related to the baseline signal.

8. The system of claim 1, wherein the measurement unit is further configured to output a stimulus signal to the touch panel and receive a response signal associated with the capacitance measurement data from the touch panel.

9. The system of claim 1, wherein the post-processing operations include detection of a touch region, calculation of a number of touches, touch coordinate calculation, touch weight calculation, finger tracing, benchmark data error monitoring, water detection, charger noise detection, or large object detection.

10. The system of claim 1, wherein the measurement unit is configured to change a hardware configuration for acquiring the capacitance measurement data.

11. The system of claim 1, wherein the measurement unit is further configured to acquire mutual capacitance measurement data from the touch panel.

17. The system of claim 1, wherein the third resistor comprises the first resistor coupled in series with another resistor.

12. A system for touch detection, the system comprising:

a signal generator configured to generate one or more selection signals;

a hybrid measurement component configured to

acquire self capacitance data from a touch panel in response to the one or more selection signals corresponding to a first set of values by switching to a first configuration in which a first capacitor and a first resistor are connected in parallel from an inverting input of an amplifier to an output of the amplifier, and a second resistor is connected from a second capacitor to the inverting input, and

acquire mutual capacitance data from the touch panel in response to the one or more selection signals corresponding to a second set of values by switching to a second configuration in which the first capacitor and the second capacitor and a third resistor are connected in parallel from the inverting input to the output; and

a signal processing component configured to determine whether a touch event occurs on the touch panel based at least in part on the self capacitance data or the mutual capacitance data.

13. The system of claim 12, wherein the hybrid measurement component is further configured to change between the first configuration and the second configuration using one or more switches, the one or more switches being closed or opened in response to the one or more selection signals.

14. The system of claim 12, further comprising:

a pre-processing unit configured to generate an activation signal in response to the detection of the touch event; and

a microcontroller unit configured to be activated in response to the activation signal to perform post-processing operations related to the touch event.

18. The system of claim 12, wherein the third resistor comprises the first resistor coupled in series with another resistor.

15. A method for touch detection, the method comprising:

acquiring capacitance measurement data from a touch panel;

detecting whether a touch event occurs on the touch panel based at least in part on;

adjusting a baseline value B by an amount (C−

B)*F, wherein C represents a capacitance measurement, and F is a predetermined factor,

generating a threshold signal value T as equal to B times a predetermined value,

generating a difference D as equal to C−

B, and

determining whether a touch event has occurred based on a comparison between D and T;

generating an interrupt signal to a microcontroller unit in response to the detection of the touch event; and

wherein the microcontroller unit (i) is in a reduced-power state prior to receiving the interrupt signal and (ii) is activated by the interrupt signal to exit the reduced-power state in order to perform post-processing operations related to the touch event;

wherein a measurement unit is further configured to;

acquire self capacitance measurement data from the touch panel by switching to a configuration in which a first capacitor and a first resistor are connected in parallel from an inverting input of an amplifier to an output of the amplifier, and a second resistor is connected from a second capacitor to the inverting input, and

acquire mutual capacitance by switching to a configuration in which the first capacitor and the second capacitor and a third resistor are connected in parallel from the inverting input to the output.

16. A method for touch detection, the method comprising:

acquiring self capacitance data from a touch panel in response to one or more selection signals corresponding to a first set of values by switching to a first configuration in which a first capacitor and a first resistor are connected in parallel from an inverting input of an amplifier to an output of the amplifier, and a second resistor is connected from a second capacitor to the inverting input;

acquiring mutual capacitance data from the touch panel in response to one or more selection signals corresponding to a second set of values by switching to a second configuration in which the first capacitor and the second capacitor and a third resistor are connected in parallel from the inverting input to the output; and

determining whether a touch event occurs on the touch panel based at least in part on the self capacitance data or the mutual capacitance data.

19. The method of claim 16, wherein the third resistor comprises the first resistor coupled in series with another resistor.