Active stylus and capacitive position detection system having touch object detecting mode and stylus detecting mode
An elongated stylus is configured to be capacitively coupled with a sensor array providing a plurality of electrodes to indicate a position on the sensor array. The stylus includes a housing having an end in an elongated direction of the housing, a conductive tip disposed at least partially extended from the end of the housing, an electrode disposed around the conductive tip and configured to at least partially expose the conductive tip, and a signal transmit drive circuit configured to provide a signal. Control is performed to form an electrical connection between the electrode and a ground and an electrical connection between the electrode and the signal transmit drive circuit when the elongated stylus is activated for capacitive coupling with the sensor array.
1. A stylus detecting system, comprising:
a sense array including first lines and second lines crossing the first lines;
a detector-side antenna; and
a touch controller connected to the sense array and configured to:
(i) in a touch object detecting mode, drive the first lines as transmission (TX) lines with a finger sensing TX signal and measure reception (RX) signals on the second lines as RX lines, and
(ii) in a stylus detecting mode, measure a stylus TX signal transmitted by a stylus, on both the first lines and the second lines, wherein, in the stylus detecting mode, the touch controller transmits synchronization or timing data wirelessly from the detector-side antenna to a stylus-side antenna inside the stylus, using magnetic coupling between the detector-side antenna and the stylus-side antenna, to cause the stylus to transmit the stylus TX signal.
2. The stylus detecting system according to claim 1 , wherein the stylus TX signal is different in either frequency or phase from a TX signal from a TX drive circuit.
3. The stylus detecting system according to claim 1 , wherein the stylus TX signal has a different code for code modulation than a code used in a TX signal from a TX drive circuit.
4. The stylus detecting system according to claim 1 , wherein the detector-side antenna provides a uniform magnetic field across a panel surface of the sensor array.
5. The stylus detecting system according to claim 1 , wherein the stylus TX signal transmitted by the stylus has a greater amplitude than the finger sensing TX signal.
6. The stylus detecting system according to claim 5 , wherein the stylus TX signal ranges approximately between 20V-50V.
7. The stylus detecting system according to claim 6 , wherein the finger sensing TX signal is less than 10V.
8. The stylus detecting system according to claim 7 , wherein the finger sensing TX signal is more than 5 V.
9. The stylus detecting system according to claim 1 , wherein the stylus TX signal has a higher frequency than the finger sensing TX signal.
10. The stylus detecting system according to claim 9 , wherein the stylus TX signal has at least double the upper frequency limit of the finger sensing TX signal.
11. A method of touch and stylus detection, comprising:
(i) in a touch object detecting mode:
driving first lines of a sense array as transmission (TX) lines with a finger sensing TX signal, and
measuring reception (RX) signals on second lines of the sense array, which cross the first lines, as RX lines; and
(ii) in a stylus detecting mode:
transmitting synchronization or timing data to a stylus, wirelessly from a detector-side antenna to a stylus-side antenna inside the stylus, using magnetic coupling between the detector-side antenna and the stylus-side antenna, to cause the stylus to transmit a stylus TX signal, and
measuring the stylus TX signal on both the first lines and the second lines.
12. The method according to claim 11 , wherein the detector-side antenna provides a uniform magnetic field across a panel surface of the sensor array.