A semiconductor fingerprint sensor image acquisition method

Abstract

The present invention relates to a semiconductor fingerprint sensor image acquisition method, which can shorten the acquisition time of a single image and improve the image acquisition efficiency. The method is implemented based on a semiconductor fingerprint sensor system, which includes: an ADC circuit, a controller, an interface circuit, an asynchronous FIFO memory, a gating circuit, and configuration and status registers. The controller is used to control the gating circuit to perform single pixel gating, control the ADC circuit to sample the gated single pixel, and control the asynchronous FIFO memory to store the acquired single pixel. The single pixel is selected, acquired, and stored in a data parallel manner. Data parallel means that the controller controls the gating circuit to select the next pixel in the pixel matrix, while the ADC circuit acquires the current pixel that has been gated, and the asynchronous FIFO memory stores the previous pixel acquired by the ADC circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of fingerprint sensors, and in particular to an image acquisition method for a semiconductor fingerprint sensor. Background Art

[0002] Semiconductor fingerprint sensors are currently a common fingerprint acquisition device, primarily utilizing principles such as capacitance, inductance, and temperature to capture fingerprint images. The fingerprint recognition process based on semiconductor fingerprint sensors generally consists of three steps: first, reading the fingerprint image from the sensor; second, performing calculations on the fingerprint image; and third, providing feedback to the user based on the calculation results. To shorten the execution time and improve feedback efficiency, reducing the runtime of any of these three steps can help reduce the response time of the entire application process.

[0003] The prior art provides a method, device, medium and electronic device for adjusting image acquisition time. The method for adjusting image acquisition time includes: obtaining an image acquisition adjustment strategy, the image acquisition adjustment strategy is mainly generated based on a target time difference, the target time difference is determined according to the time difference between the time when a display module at the receiving end receives a frame of image and the time when the display module displays the frame of image, and then adjusting the acquisition time of the next frame of image to be acquired by the sending end according to the image acquisition strategy. However, this image acquisition time adjustment method is only used for adjusting the acquisition time of the image frame received by the display module, and the acquisition time of a single frame image (i.e., a single image) remains unchanged. The common image acquisition time adjustment methods currently on the market are also all for adjusting the acquisition time of two adjacent frames of image. There are few devices or methods that can achieve single image acquisition time adjustment. Therefore, it is necessary to invent a device or method that can achieve single image (or single image fragment) acquisition time adjustment. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides an image acquisition method for a semiconductor fingerprint sensor, which can shorten the acquisition time of a single image and improve the image acquisition efficiency.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A semiconductor fingerprint sensor image acquisition method is implemented based on a semiconductor fingerprint sensor system. The semiconductor fingerprint sensor system includes a sensing end, the sensing end is used to sense a fingerprint image, and the fingerprint image is composed of a pixel matrix, and the pixel matrix includes a plurality of single pixels;

[0007] The semiconductor fingerprint sensor system includes: an ADC circuit, a controller, an interface circuit, an asynchronous FIFO memory, a gating circuit, and a configuration and status register. The ADC circuit, the asynchronous FIFO memory, the gating circuit, the configuration and status register are all electrically connected to the controller. The configuration and status register is communicatively connected to the host computer through the interface circuit. The configuration and status register is used to store user configuration or reflect the internal status of the system.

[0008] The sensing end of the semiconductor fingerprint sensor is connected to the ADC circuit through the gating circuit.

[0009] The controller is used to control the gating circuit to perform pixel gating, control the ADC circuit to sample the gated pixels, and control the asynchronous FIFO memory to store the collected pixels;

[0010] The gating circuit is used to gating individual pixels in the pixel matrix one by one;

[0011] The ADC circuit is used to collect data from a single pixel selected by the selection circuit and convert the collected analog quantity into a digital quantity;

[0012] The ADC circuit is further connected to the asynchronous FIFO memory, and the asynchronous FIFO memory is used to store a single pixel collected by the ADC circuit;

[0013] The method is characterized in that it includes: using data parallelism to select, collect, and save a single pixel, and data parallelism means: controlling the selection circuit through the controller to select the next pixel in the pixel matrix, while the ADC circuit collects the current pixel that has been selected, and the asynchronous FIFO memory stores the previous pixel that has been collected by the ADC circuit.

[0014] It is further characterized in that

[0015] The pixel matrix includes a first pixel, a second pixel, a third pixel to an nth pixel, where n is a positive integer;

[0016] The gating circuit includes a data selector mux, which is used to correspondingly select the first pixel, the second pixel, and the third pixel to the nth pixel;

[0017] Furthermore, the data selector mux includes a row selection circuit and a column selection circuit, and the row selection circuit and the column selection circuit are respectively used to select the horizontal coordinate and the vertical coordinate of a single pixel;

[0018] Furthermore, the specific steps of data parallelization include: S1, the controller controls the gating circuit to correspondingly gating the first pixel;

[0019] S2, the ADC circuit collects the first pixel in the fingerprint image pixel matrix through the gating circuit, and the controller controls the gating circuit to correspondingly gate the second pixel;

[0020] S3, the controller controls the ADC circuit to save the collected first pixel to the asynchronous FIFO memory, and at the same time, the ADC circuit collects the second pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time, the controller controls the gating circuit to correspondingly gate the third pixel;

[0021] S4, the controller controls the ADC circuit to save the collected second pixel to the asynchronous FIFO memory, and at the same time, the ADC circuit collects the second pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time, the controller controls the gating circuit to correspondingly select the fourth pixel;

[0022] And so on.

[0023] Sn-1, the controller controls the ADC circuit to save the collected n-2 pixel to the asynchronous FIFO memory, and at the same time, the ADC circuit collects the n-1 pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time, the controller controls the gating circuit to correspondingly gate the n pixel;

[0024] Sn, the controller controls the ADC circuit to save the collected n-1th pixel to the asynchronous FIFO memory, and at the same time the ADC circuit collects the nth pixel in the fingerprint image pixel matrix through the gating circuit;

[0025] Sn+1, the controller controls the ADC circuit to save the collected n-th pixel into the asynchronous FIFO memory;

[0026] Furthermore, the semiconductor fingerprint sensor system further includes: a reset circuit, a bandgap reference circuit, and a clock circuit, wherein the reset circuit is used to provide a power-on reset signal to the semiconductor fingerprint sensor system, the bandgap reference circuit is used to provide a reference voltage source to the system, and the clock circuit is used to provide a synchronous clock to the system;

[0027] The configuration and status register is also connected to the asynchronous FIFO memory for reading data stored in the asynchronous FIFO memory;

[0028] The interface circuit adopts SPI interface;

[0029] The sampling speed of the ADC circuit is 1 pixel / us;

[0030] The clock frequency of the interface circuit is 8 MHz / s;

[0031] The depth of the asynchronous FIFO memory is 8 bits;

[0032] The steps of collecting a fingerprint image by using a semiconductor fingerprint sensor system include: A1, a host computer sends a command to a configuration and status register through an interface circuit to modify configuration data in the configuration and status register;

[0033] A2. The controller controls the sensor end to sense the fingerprint image according to the configuration data;

[0034] A3, ADC circuit collects pixels of the pixel matrix in the fingerprint image one by one through the gating circuit, and saves the collected pixels into the asynchronous FIFO memory;

[0035] Furthermore, the time lengths for the ADC circuit to collect pixels, the time lengths for the gating circuit to select pixels, and the time lengths for the asynchronous FIFO memory to store pixels are the same.

[0036] The above-mentioned method of the present invention can achieve the following beneficial effects. In the semiconductor fingerprint sensor image acquisition method of the present application, fingerprint image acquisition is realized in a data parallel manner. Data parallel means that the controller controls the selection circuit to select the next pixel in the pixel matrix, and the ADC circuit collects the current pixel that has been selected. At the same time, the asynchronous FIFO memory stores the previous pixel that has been collected by the ADC circuit. This data parallel transmission method enables the selection of the next pixel to be carried out simultaneously with the collection of the selected pixel and the storage of the previous pixel that has been collected, that is, the simultaneous transmission of the selection data stream, the collection data stream, and the storage data stream is realized in the same time period, thereby greatly shortening the collection time of the entire image and improving the collection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the flow chart for collecting an existing single fingerprint image;

[0038] Figure 2 This is a structural block diagram of the semiconductor fingerprint sensor system of the present invention;

[0039] Figure 3 This is a flow chart of the present invention for collecting fingerprint images through a semiconductor fingerprint sensor system;

[0040] Figure 4 The flowchart of the data parallel method of collecting fingerprint images is shown in the figure.

[0041] Reference numerals: ADC circuit 1 , controller 2 , interface circuit 3 , asynchronous FIFO memory 4 , strobe circuit 5 , configuration and status register 6 , reset circuit 7 , bandgap reference circuit 8 , clock circuit 9 , host computer 10 . DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0043] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product or equipment that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or equipment.

[0044] Currently, the commonly used semiconductor fingerprint sensor reads fingerprint images in three steps: pixel gating, pixel acquisition, and data storage (data storage includes: pixel storage). After sending the pixel acquisition instruction, pixel gating, pixel acquisition, and data storage are performed continuously in sequence. Figure 1 That is, after pixel gating is completed, pixel acquisition is performed, and after pixel acquisition is completed, data is saved. After data saving is completed, the pixel acquisition instruction is sent again to perform gating, acquisition, and saving of the next pixel. This cycle is repeated until all pixels in the entire fingerprint image are saved. Then, a fingerprint image is synthesized on the application side, thereby realizing the upload of a single fingerprint image. Suppose the pixel gating time is T1, the pixel acquisition time is T2, and the pixel saving time is T3. The total number of pixels of a single fingerprint image is N (that is, a single fingerprint image contains N pixel grayscale values). The sampling time for acquiring a single fingerprint image using this image acquisition method is (T1+T2+T3)*N. If the clock frequency of the interface circuit is 8MHz and the grayscale value of one pixel is 1byte (i.e. 8bit), then one pixel is transmitted in 1us. If other acquisition and transmission times are not considered, the total acquisition and transmission time for a single image (or a single image fragment) is (T1+T2+T3+1)*N. It can be seen that the total acquisition and transmission time for a single image (or a single image fragment) is proportional to the number of pixels. Under the condition that the number of pixels remains unchanged, the image acquisition time can be adjusted by adjusting the values of T1+T2+T3.

[0045] The existing image acquisition method of sequentially selecting pixels, collecting pixels, and saving data has the problem of long acquisition time. To solve this problem, a semiconductor fingerprint sensor system is provided below. Figure 2The system includes an ADC circuit 1, a controller 2, an interface circuit 3, an asynchronous FIFO memory 4, a gating circuit 5, a configuration and status register 6, a reset circuit 7, a bandgap reference circuit 8, a clock circuit 9, and a sensing end. The ADC circuit 1, the asynchronous FIFO memory 4, the gating circuit 5, and the configuration and status register 6 are all electrically connected to the controller 2. The sensing end is connected to the ADC circuit 1 through the gating circuit 5. The configuration and status register 6 is communicatively connected to the host computer 10 through the interface circuit 3. The interface circuit 3 adopts an SPI interface. In this embodiment, the clock frequency of the interface circuit 3 is 8 MHz / s, that is, 1 Byte is transmitted every 1 us.

[0046] Among them, the sensing end is used to sense the fingerprint image, and the fingerprint image is composed of a pixel matrix. The pixel matrix includes a number of single pixels. In this embodiment, the pixel matrix includes a first pixel, a second pixel, a third pixel to an nth pixel, where n is a positive integer, n=N.

[0047] The controller 2 is used to control the gating circuit 5 to perform pixel gating, control the ADC circuit 1 to sample the gated pixels, and control the asynchronous FIFO memory 4 to store the sampled pixels.

[0048] The gating circuit 5 is used to select individual pixels in the pixel matrix one by one. In this embodiment, in order to facilitate the gating circuit to select n pixels in the fingerprint image, the gating circuit is a data selector mux, which is used to select the first pixel, the second pixel, the third pixel to the nth pixel respectively; the data selector mux includes a row selection circuit and a column selection circuit, and the row selection circuit and the column selection circuit respectively perform gating operations on the horizontal coordinate and the vertical coordinate of a single pixel. The gating circuit 5 adopts the existing MUX tree logic structure, and the row selection circuit and the column selection circuit can adopt existing circuits.

[0049] The ADC circuit 1 is used to collect data from a single pixel selected by the selection circuit 5 and to convert the collected pixel analog quantity into a digital quantity. The sampling speed of the ADC circuit 1 is 1 pixel / us.

[0050] The ADC circuit 1 is further connected to an asynchronous FIFO memory 4. In this embodiment, the asynchronous FIFO memory has a depth of 8 bits. The asynchronous FIFO memory 4 is used to store a single pixel collected by the ADC circuit 1.

[0051] The configuration and status register 6 is used to store user configuration or reflect the internal status of the system. The configuration and status register is also connected to the asynchronous FIFO memory and is used to read data stored in the asynchronous FIFO memory.

[0052] The reset circuit is used to provide a power-on reset signal to the semiconductor fingerprint sensor system, the bandgap reference circuit is used to provide a reference voltage source to the system, and the clock circuit is used to provide a synchronous clock to the system.

[0053] The steps of collecting fingerprint images using the semiconductor fingerprint sensor system include: A1, the host computer sends instructions to the configuration and status register through the interface circuit 3 to modify the configuration data in the configuration and status register;

[0054] A2, the controller 2 calls the configuration data in the configuration and status register 6, and controls the sensor end to sense the fingerprint image according to the configuration data;

[0055] A3, ADC circuit 1 collects pixels of the fingerprint image pixel matrix one by one through the gate circuit 5, and saves the collected pixels to the asynchronous FIFO memory 4. After the collection and storage of n pixels in the fingerprint image pixel matrix are completed, the controller synthesizes one pixel to form a complete fingerprint image (or a complete fingerprint image fragment).

[0056] In step A3, a single pixel is selected, collected, and stored in a data parallel manner. Data parallelism means that the controller 2 controls the selection circuit 5 to select the next pixel in the pixel matrix, while the ADC circuit 1 collects the selected pixel, and the asynchronous FIFO memory 4 stores the previous pixel collected by the ADC circuit 1. The specific steps of data parallelism include:

[0057] S1, the controller controls the gating circuit to correspondingly gate the first pixel;

[0058] S2, the ADC circuit collects the first pixel in the fingerprint image pixel matrix through the gating circuit, and the controller controls the gating circuit to correspondingly gate the second pixel;

[0059] S3, the controller controls the ADC circuit to save the collected first pixel to the asynchronous FIFO memory, and at the same time, the ADC circuit collects the second pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time, the controller controls the gating circuit to correspondingly select the third pixel;

[0060] S4, the controller controls the ADC circuit to save the collected second pixel to the asynchronous FIFO memory, and at the same time, the ADC circuit collects the second pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time, the controller controls the gating circuit to select the fourth pixel gating;

[0061] And so on.

[0062] Sn-1, the controller controls the ADC circuit to save the collected n-2 pixel to the asynchronous FIFO memory, and at the same time the ADC circuit collects the n-1 pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time the controller controls the gating circuit to select the n-th pixel for gating;

[0063] Sn, the controller controls the ADC circuit to save the collected n-1th pixel to the asynchronous FIFO memory, and at the same time the ADC circuit collects the nth pixel in the fingerprint image pixel matrix through the gating circuit;

[0064] Sn+1, the controller controls the ADC circuit to save the collected n-th pixel into the asynchronous FIFO memory.

[0065] In steps S2 to Sn, the time for the ADC circuit to acquire pixels, the time for the gating circuit to select pixels, and the time for the asynchronous FIFO memory to store pixels are controlled to be within the same time length. The time for the asynchronous FIFO memory to store pixels is also the time it takes to fill the asynchronous FIFO memory with acquired pixels. The time for the ADC circuit to acquire pixels is the time it takes for the analog circuit to perform signal conversion. This time length is fixed and unchanged. At a sampling rate of 1Mbyte / s, one pixel is acquired every 1us. The time for the ADC circuit to acquire pixels is set to T1, the time for the gating circuit to select pixels is set to T2, and the time for the asynchronous FIFO memory to store pixels is set to T3, where T1 is 1 microsecond. By increasing or decreasing the internal synchronous clock frequency of the semiconductor fingerprint sensor, the pixel selection time T2 is controlled to not exceed 1us. In the pixel storage link (i.e., the data storage link), if the asynchronous FIFO memory is not full, the storage time will not exceed 1us, even if T1=T2=T3. If the asynchronous FIFO memory is full, the entire acquisition process needs to be suspended. At this time, the asynchronous FIFO memory sends a signal to the controller, and the controller controls the gating circuit and the ADC circuit to maintain the current gating and acquisition state.

[0066] If the transmission speed of the interface circuit is calculated based on 8MHz, that is, the speed of reading one pixel in 1us, it is equal to the time it takes for the ADC circuit to collect one pixel. Therefore, if the transmission speed of the interface circuit exceeds 8MHz, no data can be read. If the transmission speed of the interface circuit is less than 8MHz, the asynchronous FIFO memory will be full and the controller will control the entire collection process to pause.

[0067] After adopting the semiconductor fingerprint sensor system and image acquisition method of the present application, the acquisition time of the entire image is T1*n+T1+T3. Since T1=T2=T3=1us, n=N, and n is a positive integer, the acquisition time of the entire image is N+2. If the depth of the asynchronous FIFO memory is 8bit, the acquisition and transmission time of the entire fingerprint image is N+2+8=N+10. The current commonly used single image acquisition and transmission time is

[0068] (T1+T2+T3+1)*N=4*N,

[0069] The total time for acquiring, transmitting, and storing a single image is:

[0070] 4*N+8+2=4*N+10,

[0071] N+10<4*N+10,

[0072] It can be seen that the data parallelism of the three links of pixel selection, ADC sampling and data storage effectively shortens the time for semiconductor fingerprint recognition sensors to collect images, improves the reading efficiency of fingerprint images, and thus improves the user experience of fingerprint recognition applications.

[0073] It is understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced with equivalents to achieve the same technical effects; as long as the use requirements are met, they are all within the scope of protection of the present invention.

Claims

1. A semiconductor fingerprint sensor image acquisition method, the method being implemented based on a semiconductor fingerprint sensor system. The semiconductor fingerprint sensor system includes a sensing end configured to sense a fingerprint image, wherein the fingerprint image is composed of a pixel matrix comprising a plurality of individual pixels. The semiconductor fingerprint sensor system comprises: An ADC circuit, a controller, an interface circuit, an asynchronous FIFO memory, a gating circuit, and a configuration and status register, wherein the ADC circuit, the asynchronous FIFO memory, the gating circuit, the configuration and status register are all electrically connected to the controller, and the configuration and status register is communicatively connected to the host computer via the interface circuit, and the configuration and status register is used to store user configuration or reflect the internal state of the system; The sensing end of the semiconductor fingerprint sensor is connected to the ADC circuit through the gating circuit. The controller is used to control the gating circuit to perform pixel gating, control the ADC circuit to sample the gated pixels, and control the asynchronous FIFO memory to store the collected pixels; The gating circuit is used to gating individual pixels in the pixel matrix one by one; The ADC circuit is used to collect data from a single pixel selected by the selection circuit and convert the collected analog quantity into a digital quantity; The ADC circuit is further connected to the asynchronous FIFO memory, and the asynchronous FIFO memory is used to store a single pixel collected by the ADC circuit; The method is characterized in that it includes: using data parallelism to select, collect, and save a single pixel, and data parallelism means: controlling the selection circuit through the controller to select the next pixel in the pixel matrix, while the ADC circuit collects the current pixel that has been selected, and the asynchronous FIFO memory stores the previous pixel that has been collected by the ADC circuit.

2. The semiconductor fingerprint sensor image acquisition method according to claim 1, characterized in that: The pixel matrix includes a first pixel, a second pixel, and a third pixel to an nth pixel, where n is a positive integer.

3. The semiconductor fingerprint sensor image acquisition method according to claim 2, characterized in that: The gating circuit includes a data selector mux, which is used to correspondingly select the first pixel, the second pixel, and the third pixel to the nth pixel.

4. The semiconductor fingerprint sensor image acquisition method according to claim 3, characterized in that: The data selector mux includes a row selection circuit and a column selection circuit, and the row selection circuit and the column selection circuit respectively select the horizontal coordinate and the vertical coordinate of a single pixel.

5. The semiconductor fingerprint sensor image acquisition method according to claim 4, characterized in that: The specific steps of data parallelization include: S1, the controller controls the gating circuit to correspondingly gate the first pixel; S2, the ADC circuit collects the first pixel in the fingerprint image pixel matrix through the gating circuit, and the controller controls the gating circuit to correspondingly gate the second pixel; S3, the controller controls the ADC circuit to save the collected first pixel to the asynchronous FIFO memory, and at the same time, the ADC circuit collects the second pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time, the controller controls the gating circuit to correspondingly gate the third pixel; S4, the controller controls the ADC circuit to save the collected second pixel to the asynchronous FIFO memory, and at the same time, the ADC circuit collects the third pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time, the controller controls the gating circuit to correspondingly gate the fourth pixel; And so on. Sn-1, the controller controls the ADC circuit to save the collected n-2 pixel to the asynchronous FIFO memory, and at the same time, the ADC circuit collects the n-1 pixel in the fingerprint image pixel matrix through the gating circuit, and at the same time, the controller controls the gating circuit to correspondingly gate the n pixel; Sn, the controller controls the ADC circuit to save the collected n-1th pixel to the asynchronous FIFO memory, and at the same time the ADC circuit collects the nth pixel in the fingerprint image pixel matrix through the gating circuit; Sn+1, the controller controls the ADC circuit to save the collected n-th pixel into the asynchronous FIFO memory.

6. The semiconductor fingerprint sensor image acquisition method according to claim 1 or 5, characterized in that: The time lengths for the ADC circuit to collect pixels, the time lengths for the gating circuit to gating pixels, and the time lengths for the asynchronous FIFO memory to store pixels are the same.

7. The semiconductor fingerprint sensor image acquisition method according to claim 1, characterized in that: The semiconductor fingerprint sensor system further includes: a reset circuit, a bandgap reference circuit, and a clock circuit. The reset circuit is used to provide a power-on reset signal to the semiconductor fingerprint sensor system, the bandgap reference circuit is used to provide a reference voltage source to the system, and the clock circuit is used to provide a synchronous clock to the system. The configuration and status register is also connected to the asynchronous FIFO memory for reading data stored in the asynchronous FIFO memory.

8. The semiconductor fingerprint sensor image acquisition method according to claim 7, characterized in that: The interface circuit adopts an SPI interface; the sampling speed of the ADC circuit is 1 pixel / us, and the clock frequency of the interface circuit is 8 MHz / s.

9. The semiconductor fingerprint sensor image acquisition method according to claim 8, characterized in that: The asynchronous FIFO memory has a depth of 8 bits.

10. The semiconductor fingerprint sensor image acquisition method according to claim 9, characterized in that: The steps of collecting a fingerprint image by using a semiconductor fingerprint sensor system include: A1, a host computer sends a command to a configuration and status register through an interface circuit to modify configuration data in the configuration and status register; A2. The controller controls the sensor end to sense the fingerprint image according to the configuration data; A3, ADC circuit collects pixels of the pixel matrix in the fingerprint image one by one through the gating circuit, and saves the collected pixels into the asynchronous FIFO memory.

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