CN101813996A - Touch circuit and scanning method of capacitive touch sensor - Google Patents

Abstract

The method comprises the steps of scanning a plurality of induction lines of the capacitive touch sensor in a group mode to shorten the whole scanning time and reduce the influence of noise, and after all the induction lines are scanned, performing secondary scanning on the induction lines touched by an object to more accurately position the object.

Description

Touch circuit and scanning method of capacitive touch sensor

technical field

The present invention relates to a capacitive touch sensor, in particular to a touch circuit and a scanning method of the capacitive touch sensor.

Background technique

Traditional capacitive touch sensors generally scan from the first sensing line to the last sensing line sequentially, and only scan one sensing line at a time. FIG. 1 shows a scanning method of a conventional capacitive touch sensor 10 . The capacitive touch sensor 10 is shown on the left side of FIG. 1, which includes a base plate 12 and sensing lines X1 to Xm and Y1 to Ym printed on the base plate 12, wherein the base plate 12 can be glass, plastic film or printed circuit board and other materials, the sensing lines X1 to Xm and Y1 to Ym can be metal, indium tin oxide conductive film or other material patterns. The scanning method of the capacitive touch sensor 10 is shown on the right side of FIG. 1 , which is a traditional sequential scanning method, which only scans one sensing line at a time, for example, only scanning the sensing line Y1 during time T0 to T1, Only the sensing line Y2 is scanned during time T1 to T2.

However, for a large-sized touch panel, the overall scan time of this sequential scan is too long. In addition, the noise 16 from the outside or the current source will cause the sensing lines X1 to Xm and Y1 to Ym to be affected by noise radiation, because Noise is time-varying, so the scanning time of each sensing line is inconsistent under sequential scanning, so the analog-to-digital conversion (ADC) value of each sensing line is also affected by noise radiation.

Therefore, it is desirable to provide a circuit and a scanning method that reduce noise interference and shorten the overall scanning time.

Contents of the invention

The purpose of the present invention is to provide a touch circuit and scanning method for a capacitive touch sensor.

According to the present invention, a touch circuit of a capacitive touch sensor includes a plurality of channels, a multiplexer and a front-end circuit. The scanning method includes dividing the plurality of sensing lines of the capacitive touch sensor into a plurality of groups, and the multiplexer connects the sensing lines of one group to the plurality of channels at a time, so that The front-end circuit detects the analog-to-digital conversion values of the sensing lines connected to the multiple channels at the same time. After all the sensing lines of the group are scanned, the sensing line touched by the object is found, and then the sensing line touched by the object is found. The target sensing line with the highest analog-to-digital conversion value among the sensing lines touched is centered on the target sensing line, and the nearby sensing lines are scanned again to more precisely locate the object position.

According to the technical solution of the present invention, noise interference can be reduced and the overall scanning time can be shortened.

Description of drawings

Figure 1 shows the scanning method of a conventional capacitive touch sensor;

Figure 2 shows a capacitive touch sensor;

FIG. 3 shows the scanning method of the capacitive touch sensor in FIG. 2;

Figure 4 shows parallel multiplexing and group scanning;

Figure 5 shows a secondary group scan for finger touch locations; and

Figure 6 shows the effect of noise under group scan.

Reference number

10 capacitive touch sensor

12 Bottom plate

14 Noise

20 capacitive touch sensor

22 Bottom plate

24 touch circuit

26 analog multiplexers

28 channels

30 front-end circuit

32 noise equalizer

Waveform of the ADC value of the sensing line in the 50 group Gyn

52 target sensing line

54 The waveform of the ADC value of the sensing line in the group Gx1

56 The waveform of the ADC value of the sensing line in the group Gx2

58 target sensing line

60 scan window again

62 Scan window again

Detailed ways

2 shows a capacitive touch sensor 20, which includes a base plate 22, sensing lines X1 to Xm and Y1 to Ym printed on the base plate, and a touch circuit 24, wherein the base plate 22 can be glass, plastic film or printed circuit board and other materials, the sensing lines X1 to Xm and Y1 to Ym can be metal, indium tin oxide conductive film or other material patterns. In the touch circuit 24, the analog multiplexer 26 selects a part of the sensing lines X1 to Xm and Y1 to Ym to connect to n channels 28, and the front-end circuit 30 simultaneously detects the analog-to-digital conversion of the sensing lines connected to the n channels 28 (ADC) value, a noise equalizer (noise equalizer) performs noise equalization processing on the ADC value sent by the front-end circuit 30.

FIG. 3 shows the scanning method of the capacitive touch sensor 20 in FIG. 2 . Figure 4 shows parallel multiplexing and group scanning. In the capacitive touch sensor 20, the sensing lines X1 to Xm and Y1 to Ym are divided into a plurality of preset groups, and each preset group includes n sensing lines, as shown in FIG. 4, the sensing line X1 The sensing lines Xn+1 to Xn+n are the group Gx1, the sensing lines Y1 to Yn are the group Gy1, and the sensing lines Yn+1 to Yn+n are the group Gy2. The scanning method of the present invention first performs preset group scanning, as shown in step S40 of Figure 3, the analog multiplexer 26 connects n sensing lines of a preset group to n channels 28 at a time, and the front-end circuit 30 Simultaneously scan these n sensing lines, with reference to Fig. 4, because the scanning method of the present invention scans more than two sensing lines at the same time, so can shorten the overall scanning time, and the sensing lines of the same group are scanned simultaneously, so are affected by noise radiation The degree of is relatively close, as shown on the right side of Figure 4.

Figure 5 shows a secondary group scan for finger touch locations. After all the preset groups have been scanned, proceed to step S42 to find out the sensing line touched by the finger, because the finger may fall in a group, as shown in the waveform 50 in Figure 5, the finger falls in the group Gyn, but the finger It is also possible to touch the edge of the group, as shown in the waveforms 54 and 56 of Figure 5, the fingers are between the groups Gx1 and Gx2, because the groups Gx1 and Gx2 are affected by different degrees of noise interference, there may be differences when locating the finger coordinates. Therefore, after finding the sensing line touched by the finger, the front-end circuit 30 finds out the target sensing lines 52 and 58 with the largest ADC values, and then performs group scanning again in step S44. In this step, the target sensing line 52 as the center, the analog multiplexer 26 connects the target sensing line 52 and its nearby sensing lines to n channels 28 for the front-end circuit 30 to scan, as shown in the scanning window 60 again in FIG. The line 58 is the center, and connects it and its nearby sensing lines to n channels 28 for scanning by the front-end circuit 30 , as shown in the re-scanning window 62 in FIG. 5 .

The purpose of the above steps of finding the target sensing line with the highest ADC value is to find the target sensing line with the most obvious change in sensing value. In other words, after scanning all the sensing lines, the present invention selects a target sensing line according to the scanning result, and the target sensing line may be the sensing line with the most obvious change in sensing quantity, and in some touch sensing architectures, For example, in the touch sensing method and device proposed in US Pat. No. 5,920,309, the ADC value is the highest when the change of the sensing value is the most obvious. Under the above structure, the sensing line with the highest ADC value can be selected as the target sensing line.

In different embodiments, it is also possible to select a plurality of sensing lines as target sensing lines according to the scanning result, and perform the second scanning.

Figure 6 shows the effect of noise under group scan. After completing the second group scan, since the ADC value of the sensing line touched by the finger is affected by the noise radiation at the same time, it will be shifted upward or downward, as shown in Figure 6, and then step S46 converts all sensing lines The ADC value of the line is sent to the noise equalizer 32 for noise equalization processing to improve the offset caused by the noise, thereby reducing the influence of the noise. Finally, follow-up procedures are carried out, as shown in step S48, the follow-up procedures include operations such as computing speed and acceleration.

The above description of the preferred embodiments of the present invention is for the purpose of illustration, and is not intended to limit the present invention to the disclosed form. It is possible to modify or change based on the above teachings or learning from the embodiments of the present invention. Yes, the embodiments are selected and described in order to explain the principles of the present invention and allow those skilled in the art to use the present invention in various embodiments for practical application. The technical idea of the present invention is intended to be determined by the claims and their equivalents.

Claims (9)

1. A touch circuit of a capacitive touch sensor, characterized in that, the capacitive touch sensor comprises a plurality of sensing lines, and the touch circuit comprises: multiple channels; a multiplexer, connecting the plurality of channels, selecting a part of the plurality of sensing lines to connect to the plurality of channels; and A front-end circuit is connected to the plurality of channels, and simultaneously detects the analog-to-digital conversion values of the sensing lines connected to the plurality of channels. 2 . The touch circuit according to claim 1 , wherein the front-end circuit finds the target sensing line with the largest analog-to-digital conversion value among the sensing lines touched by the object after all the sensing lines are scanned. 3. The touch control circuit according to claim 2, wherein the multiplexer connects the target sensing line and its nearby sensing lines to the multiplexer after all the sensing lines are scanned. channels for the second scan. 4. The touch circuit according to claim 3, characterized in that, the touch circuit further comprises a noise equalizer connected to the front-end circuit, after the second scan is completed, the analog-to-digital conversion of the plurality of sensing lines value for noise equalization. 5. A scanning method for a capacitive touch sensor, characterized in that the method comprises the following steps: Simultaneously scan multiple sensing lines; After all the sensing lines are scanned, selecting a target sensing line according to the scanning result; and The sensing lines near the target sensing line are scanned again to locate the object position more precisely. 6. The scanning method according to claim 5, further comprising sending the analog-to-digital conversion values of all sensing lines into a noise equalizer for noise equalization processing after the second scan is completed. 7. The scanning method according to claim 5, wherein the step of selecting a target sensing line according to the scanning result comprises using the sensing line with the most obvious change in sensing value among the sensing lines touched by the object as the target induction line. 8. The scanning method according to claim 5, wherein the step of selecting a target sensing line according to the scanning result includes using the sensing line with the highest analog-to-digital conversion value among the sensing lines touched by the object as The target sensing line. 9 . The scanning method according to claim 5 , wherein the step of re-scanning the sensing lines near the target sensing line comprises re-scanning with the target sensing line as the center.

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