1. Field of the Invention
The present invention relates to a driving method for charger noise rejection in a touch panel and more particularly to a driving method using mixed sensing modes to effectively eliminate charger noise and further enhance a frame rate of a capacitive touch panel.
2. Description of the Related Art
Since the advent of smart phones, capacitive touch panels have become an indispensable part of the smart phones. With reference to
However, during the course of operation, touch panels are prone to noise interference resulting from many environmental factors. For instance, when touch panels are applied to mobile phones, the likelihood is that the mobile phones are sensitive to interferences originating from various sources in operation. Smart phones normally consume more power attributable to their versatile functionality and oftentimes need to be recharged. Depending on the type of a charger in use, it is more likely than not that an operating mobile phone connected with the charger is subject to noise interference when the charger is a source of high noise interference and the mobile phone and a user thereof both stay in a floating state. The noise interference results in detectable capacitance values at untouched positions. The capacitance values at the untouched positions are treated as peak values, and the peak values are reported.
With reference to
An objective of the present invention is to provide a driving method using mixed sensing modes to effectively eliminate charger noise and further enhance a frame rate of a capacitive touch panel.
To achieve the foregoing objective, the driving method has steps of:
reading the sensing frame of the touch panel with a self-capacitance sensing mode, and marking at least one first-axis sensing line, wherein each one of the at least one marked first-axis sensing line has a recognizable sensing value; and
driving the at least one marked first-axis sensing line with a mutual-capacitance sensing mode to acquire at least one sensing value corresponding to at least one sensing point on each one of the at least one marked first-axis sensing line.
Preferably, the driving method further has steps of:
setting up a parameter set under the self-capacitance sensing mode;
determining if the sensing value of each sensing point on each one of the at least one marked first-axis sensing line acquired under the mutual-capacitance sensing mode is a peak value;
determining if the sensing value acquired under the self-capacitance sensing mode of each sensing point having the peak value complies with the parameter set; and
if the sensing value acquired under the self-capacitance sensing mode of each sensing point having the peak value does not comply with the parameter set, rejecting the sensing point having the peak value.
The above-mentioned driving method employs mixed sensing modes, namely a self-capacitance sensing mode and a mutual-capacitance sensing mode. The self-capacitance sensing mode is employed to identify each sensing line having a recognizable sensing value, and the mutual-capacitance sensing mode is employed to partially drive the sensing lines identified by the self-capacitance sensing mode. As the self-capacitance sensing mode is good at its anti-interference capability against charger noise, the sensing values caused by charger noise are not easy to be mistakenly acquired. In other words, each sensing line having the recognizable sensing value and acquired by the self-capacitance sensing mode has already been immune to the interference caused by charger noise. Hence, when the mutual-capacitance sensing mode is further employed to read the sensing frame, only the sensing lines filtered by the self-capacitance sensing mode are driven, thereby avoiding the false report of the coordinates of the sensing points having the sensing values caused by charger noise. Due to the sensing lines partially driven under the mutual-capacitance sensing mode, a frame rate of the touch panel is increased.
After mutual-capacitance sensing mode is employed to drive the marked sensing lines only to acquire the sensing points having the recognizable sensing values, the sensing values of the sensing points acquired under the self-capacitance sensing mode are compared with the parameter set configured under the self-capacitance sensing mode. If the sensing values of the sensing points acquired under the self-capacitance sensing mode do not comply with the condition set up in the parameter set, the sensing values of the sensing points are rejected.
The foregoing driving method can further distinguish the sensing values of the sensing points touched by a finger and caused by charger noise on the same sensing line to avoid the false report of the coordinates of the sensing points having the sensing values caused by charger noise.
Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
With reference to
Step 101: Read the sensing frame of the touch panel with a self-capacitance sensing mode, and mark at least one first-axis sensing line, wherein each one of the at least one marked first-axis sensing line has a recognizable sensing value.
Step 102: Drive the at least one marked first-axis sensing line with a mutual-capacitance sensing mode to acquire at least one sensing value corresponding to at least one sensing point on each one of the at least one marked first-axis sensing line.
As the self-capacitance sensing mode is good at its anti-interference capability against charger noise, when sensing lines are read by using the self-capacitance sensing mode and interference caused by charger noise occurs, no recognizable sensing value will appear, and only sensing values actually generated because of finger touch can be treated as recognizable sensing values. When the mutual-capacitance sensing mode is performed, the sensing lines to be driven are selected according to a result read by using the self-capacitance sensing mode. In other words, the result read under the self-capacitance sensing mode contains recognizable sensing values, and sensing lines having recognizable sensing values are selected and marked so as to get rid of interference arising from noise. Furthermore, as only the marked sensing lines are driven during the mutual-capacitance mode, a frame rate can be relatively enhanced.
With reference to
To ensure stability and accuracy of signals, when the mutual-capacitance sensing mode is employed to drive partial specific sensing lines, the sensing lines next to the sensing line having recognizable sensing values are simultaneously driven. For example, with reference to
After a specific first-axis sensing line is driven, multiple second-axis (X axis) sensing lines serve to receive the ADC raw data. A base value is subtracted from the ADC raw data to obtain sensing values of the X-axis sensing lines (dV value). Two following approaches are employed to read the X-axis sensing lines.
1. Total read option: Signals of all the X-axis sensing lines are read.
2. Partial read option: Signals of particular X-axis sensing lines are read.
The particular X-axis sensing lines denote the X-axis sensing lines having recognizable sensing values when the sensing frame is read under the self-capacitance sensing mode. Given
With reference to
Step 401: Read a sensing frame with a self-capacitance sensing mode, mark at least one sensing line, and set up a parameter set, wherein each one of the at least one sensing line has a recognizable sensing value.
Step 402: Drive the at least one marked sensing line with a mutual-capacitance sensing mode to acquire multiple sensing points, wherein each sensing point has a sensing value.
Step 403: Identify at least one of the sensing points, each of which has a peak value from the sensing points, wherein the peak value is decided by determining whether the sensing value of the present sensing point is greater than the sensing values of four surrounding sensing points and also greater than a peak threshold (PeakTH), or just by determining whether the sensing value of the present point is greater than a peak threshold.
Step 404: Determine if the sensing values of the marked sensing points read under the self-capacitance sensing mode are greater than comply with the parameter set.
Step 405: If the sensing values of the marked sensing points read under the self-capacitance sensing mode are not greater than the parameter set, reject the marked sensing points.
Step 406: If the sensing values of the marked sensing points read under the self-capacitance sensing mode are grater than the parameter set, report the marked sensing points.
The parameter set configured under the self-capacitance sensing mode in the foregoing step particularly denotes an X-axis threshold and a Y-axis threshold set up with respect to the X axis and Y axis. In other words, the acquired sensing points under the mutual-capacitance sensing mode are marked, and the sensing values of the marked sensing points acquired under the self-capacitance sensing mode are further identified. The identified sensing values are further compared with the respective X-axis threshold and Y-axis threshold. Specifically, the sensing values, which are acquired under the self-capacitance sensing mode, of the sensing lines (marked sensing lines) on which the marked sensing points are located are identified. If the acquired sensing value of each marked sensing point under the self-capacitance sensing mode is greater than the X-axis threshold and the Y-axis threshold, the sensing value of the marked sensing point is reported. Otherwise, if the sensing value of each marked sensing point that is acquired under the self-capacitance sensing mode is not greater than either one of the X-axis threshold and the Y-axis threshold, the marked sensing point is rejected. The driving method of the present embodiment can more effectively eliminate false report of sensing point caused by charger noise.
With reference to
When the sensing values of the fourth X-axis sensing line are acquired under the mutual-capacitance sensing mode, the acquired sensing values of the X-axis sensing line are further compared with the configured X-axis threshold and Y-axis threshold. As the self-capacitance sensing mode is good at its anti-interference capability against charger noise, the sensing values arising from charger noise are certainly lower than the X-axis threshold and the Y-axis threshold so that the sensing values of the sensing points arising from charger noise can be effectively ruled out. With reference to
Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Number | Date | Country | Kind |
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101106189 | Feb 2012 | TW | national |