Touch capacitive screen multi-channel scanning circuit and scanning method

Abstract

A multi-channel scanning circuit of a touch capacitive screen comprises a switch array connected with each channel, the switch array is further connected with a plurality of capacitance detection modules, and the signal input end of each capacitance detection module is connected with an analog-to-digital converter. The switch array comprises a plurality of switches and a switch control module connected between the switches and the input end of the capacitance detection module; the control logic of the switch control module is that different capacitance detection modules are controlled to be connected with different channels in different detection periods, so that each channel is detected by each capacitance detection module for the same number of times; and the analog-to-digital converter is also connected with a data processing module. The invention further discloses a touch capacitive screen multi-channel scanning method. According to the multi-channel scanning circuit of the touch capacitive screen, the scanning values of the multiple capacitance detection modules are superposed to serve as the scanning result, system noise caused by the difference between different capacitance detection modules is theoretically eliminated, and the capacitance detection precision is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, relates to a touch capacitive screen scanning technology, and specifically relates to a touch capacitive screen multi-channel scanning circuit and a scanning method. Background Art

[0002] When the capacitive screen is working, it needs to periodically scan the entire screen row by row and column by column to obtain the capacitance values ​​of all positions to determine whether a touch occurs. In the capacitive screen touch chip, in order to achieve faster response speed and support a higher number of channels, that is, resolution, multi-channel simultaneous scanning is usually selected to further complete the scanning of all channels of the entire screen.

[0003] In the prior art, when performing simultaneous scanning, multiple capacitance detection modules working simultaneously are used to scan different rows and columns respectively. Due to the performance differences between different capacitance detection modules, this will introduce circuit difference noise into the data between the channels scanned simultaneously, causing deviations in the scanning results. The same capacitance value is scanned by different capacitance detection modules, and the output results are different. At the same time, in order to overcome the random noise distributed on the time axis caused by external factors, a single channel needs to be scanned multiple times, and the accumulated results are used as the output results. After a single channel is repeatedly scanned multiple times by the same capacitance detection module, the noise caused by the circuit difference is further amplified. Summary of the invention

[0004] In view of the above defects in the prior art, the present invention discloses a touch capacitive screen multi-channel scanning circuit and a scanning method.

[0005] The touch capacitive screen multi-channel scanning circuit of the present invention comprises a switch array connected to each channel, the switch array is also connected to a plurality of capacitance detection modules, the signal input end of each capacitance detection module is connected to an analog-to-digital converter, and the switch array comprises a plurality of switches and a switch control module connected between the switch and the input end of the capacitance detection module; The control logic of the switch control module is: 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 for the same number of times; The analog-to-digital converter is also connected to a data processing module, and 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 it as the detection result of the channel.

[0006] Preferably, the switch array includes multiple groups of switches, each group of switches has N switches, N is the number of capacitance detection modules, and the N switches in each group of switches are connected to the same channel at one end and connected to different capacitance detection module input ends at the other end.

[0007] Preferably, the switch is a transmission gate or a MOS tube.

[0008] Preferably, the analog-to-digital converter is a multi-channel analog-to-digital converter, and the output ends of different capacitance detection modules are connected to different input ends of the multi-channel analog-to-digital converter.

[0009] The present invention also discloses a touch capacitive screen multi-channel scanning method, based on the touch capacitive screen multi-channel scanning circuit as described above, comprising the following steps: Step 1. Divide the total number of channels into multiple groups, and the number of channels in each group is 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 in 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.

[0010] 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 to 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.

[0011] 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.

[0012] The touch capacitive screen multi-channel scanning circuit of the present invention superimposes the scanning values ​​of multiple capacitance detection modules as the scanning result, thereby theoretically eliminating the system noise caused by the differences between different capacitance detection modules and improving the capacitance detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The figure shows a schematic diagram of a specific implementation of the touch capacitive screen multi-channel scanning circuit of the present invention; Figure 2 The figure is a schematic diagram of a specific implementation of the switch array of the present invention. DETAILED DESCRIPTION

[0014] In order to more intuitively and clearly describe the specific details of the technical solution of the present invention, a detailed description will be given below in conjunction with specific embodiments and example drawings.

[0015] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the specific implementation methods of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] like Figure 1 As shown, the touch capacitive screen multi-channel scanning circuit of the present invention includes a switch array connected to each channel, the switch array is also connected to a plurality of capacitance detection modules, the signal input end of each capacitance detection module is connected to a multi-channel analog-to-digital converter, the switch array includes a plurality of switches and a switch control module connected between the switch and the input end of the capacitance detection module, and the control logic of the switch control module is: control different capacitance detection modules to be connected to different channels respectively in different detection cycles, so that each channel is detected the same number of times by each capacitance detection module.

[0017] The multi-channel analog-to-digital converter is also connected to a data processing module, and 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 it as the detection result of the channel.

[0018] like Figure 1 A specific embodiment of the present invention is shown in the figure, the capacitive screen includes eight channels from the first channel to the eighth channel, and the touch capacitive screen multi-channel scanning circuit of the present invention includes the first to fourth capacitance detection modules. The function of the capacitance detection module is to detect the capacitance value and output an analog signal, which is a prior art in the field. Usually, the capacitance is detected by using the fact that the change of capacitance will cause the change of voltage under the constant charge state.

[0019] based on Figure 1 The touch capacitive screen multi-channel scanning circuit shown in the figure, the present invention can adopt the following touch capacitive screen multi-channel scanning method, including the following steps: Step 1. Divide the total number of channels into multiple groups, and the number of channels in each group is 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 in 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.

[0020] by Figure 1 For example, the capacitive screen includes eight channels from the first channel to the eighth channel, and the touch capacitive screen multi-channel scanning circuit of the present invention includes first to fourth capacitance detection modules.

[0021] 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 through switch actions to detect the first to fourth channels respectively, and the detection values ​​are expressed 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] respectively.

[0022] In the second detection cycle, the switch array adjusts the switch 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; 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] respectively; 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; After the above four detection cycles are completed, the first to fourth channels are detected once by the first to fourth capacitance detection modules respectively; After each detection cycle, each capacitance detection module outputs an analog signal to a multi-channel analog-to-digital converter to output a digital signal. For a single-channel analog-to-digital converter, a time-sharing sampling method can be used to input analog signals of different capacitance detection modules in different time periods for conversion and output.

[0023] After the four detection cycles are completed, the detection values ​​of the four channels are obtained and input into the data processing module for cumulative calculation processing; The sum of the four scan values ​​obtained in the first channel is D1[CT1]+D1[CT2] +D1[CT3] +D1[CT4]; The sum of the four scan values ​​obtained by the second channel is D2[CT1] +D2[CT2] +D2[CT3] +D2[CT4]; The sum of the four scan values ​​obtained by the third channel is D3[CT1] +D3[CT2] +D3[CT3] +D3[CT4]; The sum of the four scan values ​​obtained by the fourth channel is D4[CT1] +D4[CT2] +D4[CT3] +D4[CT4]; The sum of the accumulated scan values ​​is used as the scan value of the channel, so that each channel is detected by each capacitance detection module, and the difference between the channels no longer has the theoretical error caused by the difference of the capacitance detection module itself, thereby reducing circuit noise.

[0024] In the above, four detection cycles are used as one cycle, and multiple cycles can be repeated to detect the first channel to the fourth channel multiple times, thereby further reducing the error.

[0025] In the existing detection methods, the same channel is generally repeated multiple times within a certain period of time to reduce the impact of random noise generated on the time axis. In the present invention, different capacitance detection modules are used to detect the same channel respectively, which overcomes the random noise on the time axis and eliminates the circuit noise caused by the circuit performance differences between different capacitance detection modules.

[0026] Repeat the above process for the fifth to eighth channels, and so on for more channels.

[0027] If the number of remaining channels is less than four, the number of detection cycles in each cycle can be shortened accordingly so that each channel is detected the same number of times by all capacitance detection modules.

[0028] The switch array can use a transmission gate or a MOS tube as a switch. A switch is connected between each channel and each capacitance detection module. The switch array includes multiple groups of switches, each group of switches has N switches, N is the number of capacitance detection modules, and one end of the N switches in each group of switches is connected to the same channel, and the other end is connected to different capacitance detection module input ends.

[0029] like Figure 2 As shown, each channel is connected to four capacitance detection modules through four switches, and the control end of the switch is connected to the switch control module, and the switch control module controls the state of each switch according to a predetermined program.

[0030] The touch capacitive screen multi-channel scanning circuit of the present invention superimposes the scanning values ​​of multiple capacitance detection modules as the scanning result, thereby theoretically eliminating the system noise caused by the differences between different capacitance detection modules and improving the capacitance detection accuracy.

[0031] The foregoing describes various preferred embodiments of the present invention. Unless the preferred implementation modes in various preferred embodiments are obviously self-contradictory or based on a certain preferred implementation mode, various preferred implementation modes can be arbitrarily superimposed and used in combination. The embodiments and specific parameters in the embodiments are only for clearly describing the invention verification process of the inventor, and are not used to limit the patent protection scope of the present invention. The patent protection scope of the present invention shall still be based on its claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-channel scanning circuit for a touch capacitive screen, characterized in that , including a switch array connected to each channel, the switch array is also connected to a plurality of capacitance detection modules, the signal input end of each capacitance detection module is connected to an analog-to-digital converter, the switch array includes a plurality of switches and a switch control module connected between the switch and the input end of the capacitance detection module; The control logic of the switch control module is: controlling different capacitance detection modules to connect to different channels in different detection cycles, so that each channel is detected by each capacitance detection module for the same number of times; The analog-to-digital converter is also connected to a data processing module, and 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 it as the detection result of the channel.

2. The touch capacitive screen multi-channel scanning circuit according to claim 1, characterized in that: The switch array includes multiple groups of switches, each group of switches has N switches, N is the number of capacitance detection modules, and the N switches in each group of switches are connected to the same channel at one end and connected to different capacitance detection module input ends at the other end.

3. The touch capacitive screen multi-channel scanning circuit as claimed in claim 2, characterized in that: The switch is a transmission gate or a MOS tube.

4. The touch capacitive screen multi-channel scanning circuit as claimed in claim 1, characterized in that: The analog-to-digital converter is a multi-channel analog-to-digital converter, and the output ends of different capacitance detection modules are connected to different input ends of the multi-channel analog-to-digital converter.

5. A multi-channel scanning method for a touch capacitive screen, characterized in that: The touch capacitive screen multi-channel scanning circuit according to any one of claims 1 to 4 comprises the following steps: Step 1. Divide the total number of channels into multiple groups, and the number of channels in each group is 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 in 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 claimed 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, the N detection cycles in steps 2 to 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 touch capacitive screen as claimed in claim 1, characterized in that: The steps 2 and 3 are repeated multiple times for the same group of channels, and the accumulated value is taken as the detection result.

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