Multi-channel scanning circuit and scanning method for touch capacitive screen

Abstract

A multi-channel scanning circuit for a capacitive touchscreen includes a switch array connected to each channel. The switch array is also connected to multiple capacitance detection modules. The signal input terminal of each capacitance detection module is connected to an analog-to-digital converter (ADC). The switch array includes multiple switches and a switch control module connected between the switches and the input terminals of the capacitance detection modules. The control logic of the switch control module is to control different capacitance detection modules to connect to different channels in different detection cycles, ensuring that each channel is detected the same number of times by each capacitance detection module. The ADC is also connected to a data processing module. This invention also discloses a multi-channel scanning method for a capacitive touchscreen. The multi-channel scanning circuit for a capacitive touchscreen of this invention, by superimposing the scan values ​​of multiple capacitance detection modules as the scanning result, theoretically eliminates system noise caused by differences between different capacitance detection modules, thus improving capacitance detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit technology, and relates to touch capacitive screen scanning technology, specifically to a multi-channel scanning circuit and scanning method for touch capacitive screens. Background Technology

[0002] When a capacitive touchscreen is working, it needs to periodically scan the entire screen row by row and column by column to obtain the capacitance value of all positions to determine whether a touch has occurred. In capacitive touchscreen chips, in order to achieve faster response speed and support higher channel numbers, i.e. resolution, multiple channels are usually selected to scan simultaneously and further complete the scanning of all channels of the entire screen.

[0003] In existing technologies, multiple capacitance detection modules operating simultaneously scan different rows and columns during simultaneous scanning. Due to performance differences between these modules, circuit noise is introduced into the data from the simultaneously scanned channels, causing deviations in the scanning results. The same capacitance value scanned by different detection modules will result in different outputs. Furthermore, to overcome random noise distributed along the time axis caused by external factors, a single channel needs to be scanned multiple times, with the accumulated result used as the output. Repeated scanning of a single channel by the same capacitance detection module further amplifies the noise caused by circuit differences. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention discloses a multi-channel scanning circuit and scanning method for a touch capacitive screen.

[0005] The multi-channel scanning circuit for a capacitive touchscreen according to the present invention includes a switch array connected to each channel. The switch array is also connected to multiple capacitance detection modules. The signal input terminal of each capacitance detection module is connected to an analog-to-digital converter. The switch array includes multiple switches and a switch control module connected between the switches and the input terminals of the capacitance detection modules.

[0006] The control logic of the switch control module is as follows: control different capacitance detection modules to connect to different channels in different detection cycles, so that each channel is detected by each capacitance detection module the same number of times.

[0007] The analog-to-digital converter is also connected to a data processing module. The function of the data processing module is to add the detection values ​​when the same channel is connected to all different capacitance detection modules, and output the detection result of that channel.

[0008] Preferably, the switch array includes multiple sets of switches, each set of switches has N switches, where N is the number of capacitance detection modules. The N switches in each set are connected to the same channel at one end and to different capacitance detection module inputs at the other end.

[0009] Preferably, the switch is a transmission gate or a MOSFET.

[0010] Preferably, the analog-to-digital converter is a multi-channel analog-to-digital converter, and the output terminals of different capacitance detection modules are connected to different input terminals of the multi-channel analog-to-digital converter.

[0011] This invention also discloses a multi-channel scanning method for a touch capacitive screen, based on the multi-channel scanning circuit for a touch capacitive screen described above, comprising the following steps:

[0012] Step 1. Divide the total number of channels into multiple groups, with the number of channels in each group equal to the number of capacitance detection modules;

[0013] Step 2. Control the switch array so that in a single detection cycle, each channel in the same group is detected by a different capacitance detection module, and in N detection cycles, each channel in the same group is detected once by all different capacitance detection modules; N is the number of capacitance detection modules.

[0014] Step 3. Accumulate the detection values ​​of each capacitance detection module within N detection cycles according to the same channel, and use the accumulated value as the detection result;

[0015] Step 4. Traverse each group of channels and repeat steps 2 to 3 to detect all channels.

[0016] Preferably, if the number of remaining channels after grouping in step 1 is N1 and N1 is less than N, the N detection cycles in steps 2 and 3 are shortened to N1 detection cycles, so that the remaining N1 channels are detected the same number of times by all capacitance detection modules.

[0017] Preferably, steps 2 and 3 are repeated multiple times for the same group of channels, and the accumulated value is used as the detection result.

[0018] The multi-channel scanning circuit for touch capacitive screens described in this invention eliminates system noise caused by differences between different capacitance detection modules by superimposing the scan values ​​of multiple capacitance detection modules as the scanning result, thereby improving capacitance detection accuracy. Attached Figure Description

[0019] Figure 1 The diagram shown is a schematic representation of a specific embodiment of the multi-channel scanning circuit for a capacitive touchscreen according to the present invention.

[0020] Figure 2 This is a schematic diagram of a specific embodiment of the switch array described in this invention. Detailed Implementation

[0021] To more intuitively and clearly describe the specific details of the technical solution of the present invention, a detailed description will be provided below in conjunction with specific embodiments and example drawings.

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] like Figure 1 As shown, the multi-channel scanning circuit for a capacitive touchscreen of the present invention includes a switch array connected to each channel. The switch array is also connected to multiple capacitance detection modules. The signal input terminal of each capacitance detection module is connected to a multiplex analog-to-digital converter. The switch array includes multiple switches and a switch control module connected between the switches and the input terminals of the capacitance detection modules. The control logic of the switch control module is to control different capacitance detection modules to connect to different channels in different detection cycles, so that each channel is detected by each capacitance detection module the same number of times.

[0024] The multi-channel analog-to-digital converter is also connected to a data processing module. The function of the data processing module is to add the detection values ​​when the same channel is connected to all different capacitance detection modules, and output the detection result of that channel.

[0025] like Figure 1 The illustration shows a specific embodiment of the present invention. The capacitive touchscreen includes eight channels, from the first channel to the eighth channel. The multi-channel scanning circuit of the capacitive touchscreen of the present invention includes first to fourth capacitance detection modules. The function of the capacitance detection module is to detect the capacitance value and output an analog signal. This is existing technology in the field, and typically utilizes the principle that changes in capacitance under constant charge conditions will cause changes in voltage to detect capacitance.

[0026] based on Figure 1 The multi-channel scanning circuit for the touch capacitive screen shown in the present invention can employ the following multi-channel scanning method for touch capacitive screens, including the following steps:

[0027] Step 1. Divide the total number of channels into multiple groups, with the number of channels in each group equal to the number of capacitance detection modules;

[0028] Step 2. Control the switch array so that in a single detection cycle, each channel in the same group is detected by a different capacitance detection module, and in N detection cycles, each channel in the same group is detected once by all different capacitance detection modules; N is the number of capacitance detection modules.

[0029] Step 3. Accumulate the detection values ​​of each capacitance detection module within N detection cycles according to the same channel, and use the accumulated value as the detection result;

[0030] Step 4. Traverse each group of channels and repeat steps 2 to 3 to detect all channels.

[0031] by Figure 1 For example, the capacitive screen includes eight channels, from the first channel to the eighth channel. The multi-channel scanning circuit of the capacitive touch screen described in this invention includes the first to fourth capacitance detection modules.

[0032] When scanning each channel, a cycle-by-cycle operation is adopted in terms of timing. In the first detection cycle, the switch array controls the first to fourth capacitance detection modules to detect the first to fourth channels respectively through switching actions. The detection value is represented in the form of channel number [capacitance detection module number]. For example, the first to eighth channels are numbered D1 to D8 respectively, and the first to fourth capacitance detection modules are numbered CT1 to CT4. Then the four detection data obtained in the first detection cycle are D1[CT1], D2[CT2], D3[CT3], and D4[CT4].

[0033] In the second detection cycle, the switch array adjusts the switching state so that the first to fourth capacitance detection modules detect the second channel, the first channel, the fourth channel and the third channel respectively, and the four detection data obtained are D1[CT2], D2[CT1], D3[CT4] and D4[CT3] respectively;

[0034] In the third detection cycle, the first to fourth capacitance detection modules detect the third channel, the fourth channel, the first channel, and the second channel respectively, and the four detection data obtained are D1[CT3], D2[CT4], D3[CT1], and D4[CT2].

[0035] In the fourth detection cycle, the first to fourth capacitance detection modules detect the fourth channel, the third channel, the second channel and the first channel respectively, and the four detection data obtained are D1[CT4], D2[CT3], D3[CT2] and D4[CT1] respectively;

[0036] After the above four detection cycles are completed, the first to fourth channels were detected once by the first to fourth capacitance detection modules, respectively.

[0037] After each detection cycle, each capacitance detection module outputs an analog signal to a multiplexer analog-to-digital converter (ADC) to output a digital signal. For a single-channel ADC, a time-division sampling method can be used to input analog signals from different capacitance detection modules at different time periods for conversion and output.

[0038] After four detection cycles, the detection values ​​of the four channels are obtained and input into the data processing module for cumulative calculation.

[0039] The sum of the four scan values ​​obtained from the first channel is:

[0040] D1[CT1]+D1[CT2] +D1[CT3] +D1[CT4];

[0041] The sum of the four scan values ​​obtained from the second channel is

[0042] D2[CT1] +D2[CT2] +D2[CT3] +D2[CT4];

[0043] The sum of the four scan values ​​obtained from the third channel is

[0044] D3[CT1] +D3[CT2] +D3[CT3] +D3[CT4];

[0045] The sum of the four scan values ​​obtained from the fourth channel is

[0046] D4[CT1] +D4[CT2] +D4[CT3] +D4[CT4];

[0047] The sum of the accumulated scan values ​​is used as the scan value of that channel, so that each channel is detected by each capacitance detection module. The difference between channels no longer has the theoretical error caused by the difference of the capacitance detection modules themselves, thus reducing circuit noise.

[0048] The above method uses four detection cycles as one cycle, and multiple cycles can be repeated to detect the first to fourth channels multiple times, further reducing errors.

[0049] In existing detection methods, the same channel is usually tested multiple times within a certain period of time to reduce the impact of random noise generated on the time axis. In this invention, different capacitance detection modules are used to test the same channel separately, which overcomes random noise on the time axis and eliminates circuit noise caused by differences in circuit performance between different capacitance detection modules.

[0050] Repeat the above process for channels 5 through 8, and so on for additional channels.

[0051] For channels with fewer than four remaining, shorten the number of detection cycles in each loop accordingly, so that each channel is detected the same number of times by all capacitance detection modules.

[0052] The switch array can use transmission gates or MOSFETs as switches. Each channel is connected to each capacitance detection module. The switch array includes multiple groups of switches, with N switches in each group, where N is the number of capacitance detection modules. One end of each of the N switches in each group is connected to the same channel, and the other end is connected to the input terminals of different capacitance detection modules.

[0053] like Figure 2 As shown, each channel is connected to four capacitance detection modules via four switches. The control terminals of the switches are connected to the switch control module, which controls the state of each switch according to a predetermined program.

[0054] The multi-channel scanning circuit for touch capacitive screens described in this invention eliminates system noise caused by differences between different capacitance detection modules by superimposing the scan values ​​of multiple capacitance detection modules as the scanning result, thereby improving capacitance detection accuracy.

[0055] The foregoing descriptions are preferred embodiments of the present invention. Unless there is a clear contradiction between the preferred embodiments or a prerequisite for a particular preferred embodiment, the preferred embodiments can be arbitrarily combined and used. The embodiments and specific parameters described are only for clearly illustrating the inventor's invention verification process and are not intended to limit the scope of patent protection of the present invention. The scope of patent protection of the present invention shall still be determined by its claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A multi-channel scanning circuit for a touch capacitive screen, characterized in that... The system includes a switch array connected to each channel, and the switch array is also connected to multiple capacitance detection modules. The signal input terminal of each capacitance detection module is connected to an analog-to-digital converter. The switch array includes multiple switches and a switch control module connected between the switches and the input terminals of the capacitance detection modules. The control logic of the switch control module is as follows: control different capacitance detection modules to connect to different channels in different detection cycles, so that each channel is detected by each capacitance detection module the same number of times. The analog-to-digital converter is also connected to a data processing module. The function of the data processing module is to add the detection values ​​when the same channel is connected to all different capacitance detection modules, and output the detection result of that channel.

2. The multi-channel scanning circuit for a capacitive touchscreen as described in claim 1, characterized in that, The switch array includes multiple sets of switches, with N switches in each set, where N is the number of capacitance detection modules. The N switches in each set are connected to the same channel at one end and to different capacitance detection module inputs at the other end.

3. The multi-channel scanning circuit for a capacitive touchscreen as described in claim 2, characterized in that, The switch is a transmission gate or a MOSFET.

4. The multi-channel scanning circuit for a capacitive touchscreen as described in claim 1, characterized in that, The analog-to-digital converter is a multi-channel analog-to-digital converter, and the output terminals of different capacitance detection modules are connected to different input terminals of the multi-channel analog-to-digital converter.

5. A multi-channel scanning method for a touch capacitive screen, characterized in that, The multi-channel scanning circuit for a capacitive touchscreen according to any one of claims 1 to 4 includes the following steps: Step 1. Divide the total number of channels into multiple groups, with the number of channels in each group equal to the number of capacitance detection modules; Step 2. Control the switch array so that in a single detection cycle, each channel in the same group is detected by a different capacitance detection module, and in N detection cycles, each channel in the same group is detected once by all different capacitance detection modules; N is the number of capacitance detection modules. Step 3. Accumulate the detection values ​​of each capacitance detection module within N detection cycles according to the same channel, and use the accumulated value as the detection result; Step 4. Traverse each group of channels and repeat steps 2 to 3 to detect all channels.

6. The multi-channel scanning method for a touch capacitive screen as described in claim 1, characterized in that, If the number of remaining channels after grouping in step 1 is N1 and N1 is less than N, then the N detection cycles in steps 2 and 3 are shortened to N1 detection cycles, so that the remaining N1 channels are detected the same number of times by all capacitance detection modules.

7. The multi-channel scanning method for a capacitive touchscreen as described in claim 1, characterized in that, Steps 2 and 3 are repeated multiple times for the same group of channels, and the accumulated value is used as the detection result.

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