Stylus to host synchronization using a magnetic field
A system and method for synchronizing a stylus to a capacitive sense array. The system including a capacitive sense array which includes a plurality of electrodes. A magnetic field is generated using the plurality of electrodes. The magnetic field is used to synchronize the operation of the stylus and the capacitive sense array.
1. A signal processing device that is used with an active stylus which transmits a stylus transmission signal, and that is configured to be coupled to a sensor array including a plurality of first electrodes disposed along a first direction and a plurality of second electrodes disposed along a second direction different from the first direction, the signal processing device comprising:
a signal generator configured to generate a first sensor transmission signal and a second sensor transmission signal that are transmitted via the sensor array, wherein the first sensor transmission signal is transmitted to the active stylus via the sensor array and is distinguishable from the stylus transmission signal in signal types, the stylus transmission signal being modulated based on at least one of amplitude, frequency, phase, or a first code, and the second sensor transmission signal is for sensing passive object on the sensor array and is based on a second code, so that the second sensor transmission signal is distinguishable from the stylus transmission signal that is modulated based on at least one of amplitude, frequency, phase, or the first code; and
a processor coupled to the signal generator and configured to:
transmit the first sensor transmission signal to the active stylus via the sensor array, the first sensor transmission signal synchronizing a timing of the stylus transmission signal to the first sensor transmission signal, so that the stylus transmission signal is transmitted responsive to the first sensor transmission signal and a time interval of the stylus transmission signal does not overlap a time interval of the first sensor transmission signal; and
detect the active stylus from first signals received via the first and second electrodes of the sensor array in response to the stylus transmission signal, and detect the passive object from second signals received via at least one of the first and second electrodes of the sensor array in response to the second sensor transmission signal.
2. The signal processing device of claim 1 , wherein the second transmission signal is code modulated.
3. The signal processing device of claim 1 , wherein the second transmission signal has a transmission signal voltage lower than a transmission signal voltage of the stylus transmission signal.
4. The signal processing device of claim 1 , wherein the first sensor transmission signal is a burst signal.
5. The signal processing device of claim 1 , wherein one or more of the first electrodes and the second electrodes of the sensor array, in operation, receive the stylus transmission signal after the first sensor transmission signal is transmitted by the processor.
6. The signal processing device of claim 1 , wherein one or more of the first electrodes and the second electrodes of the sensor array, in operation, receive the stylus transmission signal during a first period of time, and the first sensor transmission signal is transmitted by the processor during a second period of time, the first period of time being different from the second period of time.
7. A signal processing device that is used with an active stylus which transmits a stylus transmission signal, and that is configured to be coupled to a sensor array including a plurality of first electrodes disposed along a first direction and a plurality of second electrodes disposed along a second direction different from the first direction, the signal processing device comprising:
a signal generator configured to generate a first sensor transmission signal and a second sensor transmission signal that are transmitted via the sensor array, wherein the first sensor transmission signal is transmitted to the active stylus via the sensor array and is distinguishable from the stylus transmission signal in signal types, the stylus transmission signal being modulated based on at least one of amplitude, frequency, phase, or a first code, and the second sensor transmission signal is for sensing passive object on the sensor array and is based on a second code, so that the second sensor transmission signal is distinguishable from the stylus transmission signal that is modulated based on at least one of amplitude, frequency, phase, or the first code; and
a processor coupled to the signal generator and configured to:
transmit the first sensor transmission signal to the active stylus via the sensor array to synchronize a timing of the stylus transmission signal to the first sensor transmission signal, so that the stylus transmission signal is transmitted responsive to the first sensor transmission signal; and
detect the active stylus from first signals received via the first and second electrodes of the sensor array in response to the stylus transmission signal while a time interval of the first sensor transmission signal that synchronizes a timing of the stylus transmission signal to the first sensor transmission signal overlaps a time interval of the stylus transmission signal transmitted from the active stylus, and detect the passive object from second signals received via at least one of the first and second electrodes of the sensor array in response to the second sensor transmission signal.
8. The signal processing device of claim 7 , wherein the second transmission signal is code modulated.
9. The signal processing device of claim 7 , wherein the second transmission signal has a transmission signal voltage that is lower than a transmission signal voltage of the stylus transmission signal.
10. The signal processing device of claim 7 , wherein the first sensor transmission signal is a burst signal.
11. The signal processing device of claim 7 , wherein one or more of the first electrodes and the second electrodes of the sensor array, in operation, receive the stylus transmission signal while the first sensor transmission signal is transmitted by the processor.
12. The signal processing device of claim 7 , wherein one or more of the first electrodes and the second electrodes of the sensor array, in operation, receive the stylus transmission signal during a first period of time, and the first sensor transmission signal is transmitted by the processor during a second period of time, the first period of time overlapping the second period of time.