CAPACITIVE STYLUS WITH PALM REJECTION

• US 20120105361A1
• Filed: 08/19/2011
• Published: 05/03/2012
• Est. Priority Date: 10/28/2010
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: KREMIN, VIKTOR, OGIRKO, ROMAN, PIROGOV, OLEKSANDR, RYSHTUN, ANDRIY, VALLIS, DARRIN
• Granted Patent: US 9,658,720 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• 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 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• 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
• CPC Class Codes: G06F 3/046 by electromagnetic means

Abstract

A system comprising a sensing device and a capacitive sense array configured to detect a presence of a passive touch object and a stylus where the capacitive sense array receives a transmit signal from the stylus via capacitive coupling. The system further comprising a processing device configured to determine the stylus location on the capacitive sense array based on the transmit signal and to synchronize the stylus to the capacitive sense array.

A system further comprises a demodulation block to extract additional data that is modulated into the transmit signal by the stylus. The demodulation block is configured to extract the additional data by amplitude shift keying. The additional data comprises at least one of an applied force value of the stylus tip, a button status data, a battery status data, or a stylus acceleration data.

Claims

1. An apparatus comprising:

a capacitive sense array configured to detect a presence of a passive touch object and a stylus, wherein the capacitive sense array is configured to receive a first signal from the stylus via capacitive coupling; and

a processing device, coupled to the capacitive sense array, configured to determine the stylus location on the capacitance sense array based on the first signal, and the processing device further configured to wirelessly transmit a second signal to the stylus, the second signal to synchronize the stylus to the capacitive sense array.

2. The apparatus of claim 1, wherein the first signal and second signal are the same signal.

3. The apparatus of claim 1, wherein the capacitive sense array is configured to operate as a mutual capacitance sense array in a first mode and as a coupled-charge receiver in a second mode.

4. The apparatus of claim 1, wherein the processing device is configured to substantially simultaneously track the position of both the passive touch object and the stylus on the capacitive sense array.

5. The apparatus of claim 4, wherein the capacitive sense array is configured to operate as a mutual capacitance sense array during the tracking of the position of the passive touch object in a first mode, and wherein the capacitive sense array is configured to operate as a coupled-charge receiver during the tracking of the position of the stylus in a second mode.

6. The apparatus of claim 1, wherein the capacitive sense array comprises row electrodes and column electrodes, wherein the processing device is configured to track the position of the stylus utilizing both the row electrodes and column electrodes as receive (RX) electrodes, and wherein the processor device is configured to track the position of the passive touch object using one of the row electrodes or column electrodes as the RX electrodes.

7. The apparatus of claim 1, wherein the processing device comprises a demodulation block to extract additional data that is modulated into the first signal by the stylus.

8. The apparatus of claim 7, wherein the demodulation block is configured to extract the additional data by demodulating the first signal by at least one of amplitude shift keying, frequency shift keying, binary phase shift keying, or quadrature phase shift keying.

9. The apparatus of claim 1, wherein the passive touch object is a finger and the stylus is an active stylus.

10. The apparatus of claim 1, wherein the processing device is further configured to retrieve additional data that is time division multiplexed (TDM) into the first signal.

11. A method comprising:

wirelessly communicating a transmit (TX) signal from a processing device to a stylus over a communication link between the processing device and the stylus, wherein the processing device is a timing master for synchronizing the stylus to a capacitive sense array;

receiving the TX signal at the capacitive sense array from the stylus via a capacitive coupling between the capacitive sense array and the stylus; and

synchronizing the stylus to the capacitive sense array by the processing device for finger position tracking of a touch object on the capacitive sense array and for stylus position tracking of the stylus on the same capacitive sense array.

12. The method of claim 11, wherein the capacitive sense array is configured to operate in a first mode for the finger position tracking of the touch object and a second mode for the stylus position tracking of the stylus, and wherein the method further comprises:

switching the capacitive sense array between the first mode and the second mode after said synchronization.

13. The method of claim 12, wherein the capacitive sense array comprises row electrodes and column electrodes, and wherein the method further comprises:

receiving the TX signal from the stylus using both the row electrodes and the column electrodes in the second mode for the stylus position tracking of the stylus; and

receiving a second TX signal using one of the row electrodes or the column electrodes in the first mode for finger position tracking of the touch object, wherein the second TX signal is applied to the other one of the row electrodes or the column electrodes in the first mode, and wherein the second TX signal is synchronized with the TX signal.

14. The method of claim 13, further comprising:

performing the finger position tracking;

performing the stylus position tracking substantially simultaneously with said performing the finger position tracking; and

differentiating the positions of the stylus and the touch object using at least one of frequency modulation, amplitude modulation, phase modulation, or code modulation.

15. The method of claim 14, wherein said differentiating further comprises demodulating the TX signal to extract additional data that is modulated into the TX signal by at least one of amplitude shift keying, frequency shift keying, binary phase shift modulation, or quadrature phase shift modulation.

16. The method of claim 11, wherein the wireless communicating further comprises:

generating a carrier frequency by the processing device;

modulating the carrier frequency with the TX signal by the processing device; and

transmitting the modulated TX signal from the processing device to the stylus.

17. The method of claim 16, wherein the carrier frequency is a radio-frequency identification (RFID) frequency.

18. A system comprising:

a capacitive sense array;

a stylus; and

a sensing device coupled to the capacitive sense array, wherein the sensing device is configured to wirelessly transmit a TX signal to the stylus via a communication link, wherein the TX signal synchronizes the stylus to the capacitive sense array; and

wherein the stylus is configured to provide the TX signal to the capacitive sense array via capacitive coupling to allow the sensing device to track the position of the stylus using the capacitive sense array.

19. The system of claim 22, wherein the capacitive sense array is configured to substantially simultaneously track positions of both a passive touch object and the stylus using the capacitive sense array.

20. The system of claim 22, wherein the capacitive sense array is configured to operate as a mutual capacitance sense array during the tracking of the position of the passive touch object in a first mode, and wherein the capacitive sense array is configured to operate as a coupled-charge receiver during the tracking of the position of the stylus in a second mode.