System and method for phase error compensation in synchronized devices
A system and method for compensating for detected phase errors during communications between synchronized devices. In an embodiment, the two devices may be a touch screen device and a synchronized stylus device. To this end, the touch screen device includes a controller configured to receive data signals from the stylus at specific time intervals. The touch screen device generates an internal control signal for receiving the incoming data signals at an expected frequency. The touch screen device further includes circuitry for measuring differences in the time a data signal is actually received against when the data signal was expected to be received and determines a time difference (e.g., a phase error). Then, the internal control signal may be adjusted to compensate for the accumulated phase error. Such a measurement and compensation helps ensure that communications remain in synchronization without having to reestablish synchronization through a cumbersome synchronization process.
1. A controller for processing a stylus signal including a plurality of data packages, wherein each data package includes plural data pulses, the controller comprising:
a charge-to-voltage converter configured to receive said stylus signal and enabled to perform data pulse edge detection by a periodic enable control signal and output an edge detection pulse for each data pulse edge;
a processor configured to set a phase of said periodic enable control signal by performing an initial synchronization operation with a stylus that generates said stylus signal;
a circuit configured to determine with respect to a current data package of said stylus signal a time delay between each edge detection pulse and a corresponding edge of the periodic enable control signal for the plural data pulses within said current data package; and
an adjuster configured to adjust said phase of the periodic enable control signal for the charge-to-voltage converter to perform data pulse edge detection with respect to all of the plural data pulses within a subsequent data package immediately following said current data package based on an accumulation of the determined time delays for the detected data pulse edges of all of the plural data pulses within said current data package.
2. The controller of claim 1 , wherein the charge-to-voltage converter is configured to capacitively receive the stylus signal and further configured to compare the received stylus signal to a common mode voltage and to generate an output voltage signal related to the received stylus signal based on the comparison.
3. The controller of claim 2 , further comprising a comparator configured to compare the output voltage signal to a threshold value and to generate the edge detection pulse if the output voltage signal reaches or exceeds the threshold value.
4. The controller of claim 1 , further comprising a high frequency clock configured to generate the phase of the periodic enable control signal.
5. The controller of claim 1 , wherein the adjustment of the phase comprises a leading shift in the phase of the periodic enable control signal.
6. The controller of claim 1 , wherein the adjustment of the phase comprises a lagging shift in the phase of the periodic enable control signal.
7. The controller of claim 1 , wherein the adjuster is further configured to adjust the phase based on a difference between the accumulation of the determined time delays and an expected time delay.
8. The controller of claim 1 , wherein the adjuster is further configured to adjust the phase based on a difference between an average time delay determined from the accumulation of the determined time delays and a typical time delay.
9. The controller of claim 1 , wherein the adjuster is further configured to adjust the phase based on an average time delay determined from the accumulation of the determined time delays.
10. A processor, comprising:
an input configured to receive a pulsed signal wherein each pulse of said pulsed signal corresponds to a detected edge of a data pulse within a stylus signal that includes a plurality of data packages, wherein each data package includes plural data pulses;
a clock circuit configured to generate a periodic enable control signal having a phase set in response to an initial synchronization with a stylus generating said stylus signal;
a circuit configured to determine with respect to a current data package of said stylus signal a time delay between each pulse of said pulsed signal and a corresponding edge of the periodic enable control signal for all of the plural data pulses within said current data package received from said synchronized stylus after said initial synchronization;
an adjuster configured to adjust said phase of the periodic enable control signal for all of the data pulses within a subsequent data package immediately following said current data package based on an accumulation of the determined time delays associated with detected data pulse edges of all of the plural data pulses within said current data package signal.
11. The processor of claim 10 , wherein the adjuster further configured to adjust the phase based on a difference between the accumulation of the determined time delays and an expected time delay.
12. The processor of claim 10 , wherein the adjuster is further configured to adjust the phase based on an average time delay determined from the accumulation of the determined time delays.
13. An integrated circuit, comprising:
a charge-to-voltage converter configured to receive a stylus signal including a plurality of data packages, each data package including a plurality of data pulses, from a stylus and output an edge detection pulse for each data pulse edge, said charge-to-voltage converter being enabled to perform data pulse edge detection by a periodic enable control signal;
a processor configured to set a phase of said periodic enable control signal by performing an initial synchronization operation with the stylus that generates said stylus signal;
a circuit configured to determine with respect to a current data package of said stylus signal a time delay between each edge detection pulse and a corresponding edge of the periodic enable control signal for all of the plurality of data pulses within said current data package and further determine an average value of the determined time delays for said plurality of data pulses within the current data package;
an adjuster configured to adjust said phase of the periodic enable control signal for the charge-to-voltage converter to perform data pulse edge detection with respect to all of the plurality of data pulses within a next received data package immediately following the current data package based on the determined average value of the time delays.
14. The integrated circuit of claim 13 , wherein the adjuster is further configured to adjust the phase based on a difference between the determined average value and an expected value.
15. The integrated circuit of claim 13 , further comprising a single integrated circuit die.
16. The integrated circuit of claim 13 , further comprising multiple integrated circuit dies.
17. A method, comprising:
enabling with a periodic enable control signal an edge detection circuit to perform a detection of a data pulse edge of each data pulse within a received stylus signal including a plurality of data packages, wherein each data package includes plural data pulses;
performing an initial synchronization with a stylus generating said stylus signal to set a phase of the periodic enable control signal;
determining with respect to a current data package of said stylus signal a time delay between each detected data pulse edge and a corresponding edge of the periodic enable control signal for the plural data pulses within said current data package of the stylus signal received from the synchronized stylus after said initial synchronization; and
adjusting said phase of the periodic enable control signal to for enable the edge detection circuit to perform data pulse edge detection with respect to all of the plural data pulses within a subsequent data package immediately following said current data package based on an accumulation of the determined time delays for all of the plural data pulses within the current data package signal.
18. The method of claim 17 , further comprising:
capacitively receiving the stylus signal;
comparing the received stylus signal to a common mode voltage; and
generating an output voltage signal related to the received stylus signal based on the comparison.
19. The method of claim 18 , further comprising:
comparing the output voltage signal to a threshold value; and
generating the edge detection pulse if the output voltage signal reaches or exceeds the threshold value.
20. The method of claim 17 , further comprising generating the phase of the periodic enable control signal from a high frequency clock.
21. The method of claim 17 , further comprising generating a leading shift in the phase of the periodic enable control signal.
22. The method of claim 17 , further comprising generating a lagging shift in the phase of the periodic enable control signal.
23. The method of claim 17 , further comprising adjusting the phase based on a difference between the accumulation of the determined time delays and an expected time delay.
24. The method of claim 17 , further comprising adjusting the phase based on a difference between an average time delay determined from the accumulation of the determined time delays and a typical time delay.
25. The method of claim 17 , further comprising adjusting the phase based on an average time delay determined from the accumulation of the determined time delays.