Design of a bank evaluator based on S3C2440A

Information technology is an important driving force for the economic and social development of the world today. The electronic information industry is a strategic, basic and leading pillar industry of the national economy. It plays a very important role in promoting social employment, driving economic growth, adjusting industrial structure, changing development methods and maintaining national security. With the further development of the electronics industry, the development and application of embedded systems has become one of the first choices for more and more companies to develop products. People have also experienced the power of embedded systems in different industries and fields.
With the development of the electronics industry, a large number of electronic devices have also been widely used in the banking system. As a bank in the window service industry, how to retain customers and improve service quality has become one of the key issues for banks to consider. Therefore, by establishing a direct and objective service evaluation system, service personnel can better understand their customers, make up for their own shortcomings, tap potential needs, and launch more warm services. Customer opinions are the benchmark for improving services, respecting customer opinions is an important way to win trust, and paying attention to service quality and strengthening service measures have now been recognized by the window service industry
. For this reason, the emergence of bank evaluators has become necessary.
Early bank evaluators mostly used simple digital tubes to display numbers accompanied by a few simple statements to implement a customer evaluation process. The method was too simple, and each evaluator was independent of each other and could not share resources, which brought a lot of inconvenience to the entire bank window service system. Later, microprocessors such as single-chip microcomputers were gradually introduced, but some functions were still single. Until the emergence of embedded systems, the bank evaluators developed based on embedded systems greatly changed their previous single functions.
Here we propose a design scheme for a bank evaluator based on S3C2440A and XL95144XL.

1 Introduction to ARM9
ARM microprocessor is a high-performance, low-power 32-bit microprocessor, which is widely used in embedded systems. ARM9 represents the mainstream processor of ARM company and has been widely used in electronics, electrical, communications, defense and other industries. Among them, the embedded development platform developed based on Samsung ARM9 embedded processors S3C2410 and S3C2440 performed extremely well, and the S3C2410 and S3C2440 embedded systems provide a lot of open software without any technical reservations. It can be said that these two are the most widely used embedded microprocessors in domestic open embedded products.

2 Bank Evaluator Hardware Design
The most basic function of a bank evaluator is: customers come to handle business - the teller presses the "Start" button - the voice greeting "Welcome" - the customer completes the business - the teller presses the "End" button - the voice prompt "Hello, please evaluate my service" - the customer presses the button to evaluate. Of course, with the development of embedded systems, a bank evaluator not only leaves a good impression on customers in terms of sound, but also begins to pay attention to visual effects. At the same time, other functions can be added according to the needs of each bank. The following is an
ARM9 bank evaluator designed in this article. The structural block diagram of the hardware part is shown in Figure 1.

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2.1 Embedded Minimum System
The circuit of this part is based on the ARM9 microprocessor as the core, and the corresponding memory is added to the periphery to realize the basic operation of the embedded operating system. The S3C2440A microprocessor is selected as the CPU processor, the K9F1208 NAND flash chip is used as the extended EPROM memory, two HY57V561620 chips are used as extended SDRAM, and one XL95144XL model CPLD is used in conjunction with the CPU. In addition, two crystal oscillator circuits are set up, one crystal oscillator is 16.934 4 MHz, and after frequency division in the CPU, it is used to provide the operating frequency for the CPU; the other is 32.768 kHz, which provides the operating frequency for the REAL TIME CLOCK of the S3C2440.
The core components of this part of the embedded minimum system circuit are S3C2440A and XL95144XL.
S3C2440A is a 16/32-bit RISC microprocessor launched by Samsung, which can work at a maximum operating frequency of 400 MHz. It uses the ARM920T core, has low power consumption, is easy to use, has a system manager, NAND boot boot, CACHE memory, etc., provides 60 interrupt sources, 154 general I/O ports, LCD/touch screen interface and other related data communication ports.
The second most important component is XILINX's XL95144XL. XL95144XL is a high-performance, low-power 3.3 V working CPLD. In many embedded systems, CRLD is an indispensable part, which can play a role in coordination control and distribution processing. The CPLD hardware circuit is composed of many different functional blocks, and the software part is usually implemented in VHDL or Verilog HDL programming language.
2.2 Power supply circuit
The power supply circuit mainly provides the required working voltage for each part of the hardware circuit. The S3C2440A microprocessor has two working voltages of 3.3V and 1.3V, while the working voltage of the LCD screen is about 13.6V. If a reliable working voltage is not provided, the working performance of the product cannot be guaranteed. Therefore, in this part, two sets of voltage power supply methods are used. One is to directly provide the working voltage through a 5V DC power supply, and the second is to use the network power supply method. This method is to use the Internet method, and the DC output MODEM supplies power to the circuit through the Internet port plug. This voltage is usually a 48 V DC signal, so it must be converted into a 5 V DC voltage through a power module. At the same time, a power processor TPS65150 from TI is used to convert the 13.6 V LCD screen working voltage.
Figure 2 is a circuit that converts 5 V DC voltage to 3.3 V, and Figure 3 is a circuit that converts 3.3 V to 1.3 V.

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2.3 LCD display circuit and touch screen circuit
The bank evaluator introduced in this article uses an LCD screen to dynamically display data information and pictures, which greatly improves the visual effect compared to the previous digital tube single display method.
The LCD screen uses a two-way backlight 13.6 V powered TFT LCD screen from TRULY, which combines the functions of image display and touch screen. The LCD display circuit is mainly to provide the LCD screen with a suitable working voltage. The LCD screen requires multiple voltages to be powered together, including VGH, VGL, and VCOM voltages to realize backlight and LCD display power supply. The
touch screen circuit is relatively simple, with only one 4-pin interface, through which the X and Y coordinate values ​​of the touch position are transmitted to S3C2440A for processing in the form of electrical signals, and then the touch point position is displayed on the display screen, or the corresponding function is executed. Figure 4 is the touch screen interface circuit.

2.4 Audio Circuit
The audio circuit is an indispensable part of the bank evaluator. The quality of sound is also an indicator of the quality of the evaluator. The main consideration in designing an audio circuit is the power of the audio circuit. According to the customer's requirements, the maximum amplifier power of the circuit is set to 0.7 W. The UDA1341 audio amplifier is selected. It has a strong driving ability. Under continuous power supply, it can directly drive the headphones without adding other amplifiers. The sound quality is good and there is no noise. In addition, the audio circuit also provides a speaker external speaker function.
The circuit diagram of the audio circuit is shown in Figure 5.

3 Bank evaluator software design
The software development of the bank evaluator mainly involves two parts of software programming: one is the development and transplantation of embedded operating systems; the other is the development and testing of some application software.
3.1 Embedded operating system Linux development The
embedded operating system has always been the symbol of the embedded system, and it has the characteristics of small size, strong real-time performance, and good development environment. Therefore, it is increasingly favored by everyone in many electronic products. There are many common embedded operating systems on the market. μCOS-II, Linux, μClinux, WinCE are all widely used embedded systems. This article uses the common Linux system.
Linux is an innate network operating system, mature and stable. Linux is open source software, there is no black box technology, anyone can modify it, or use it to develop their own products. The Linux system can be customized, and the system kernel can now be made very small.
The development of the Linux embedded operating system is inseparable from the C language. Many C programs are debugged and tested by the GCC compiler under the Linux system. This paper combines hardware circuits and the connection method between S3C-2440A microprocessor and peripheral circuits to program and debug the functional blocks of each part of S3C2440A separately, and test whether the circuit is correct and whether the program is correct. In addition, the transplantation of Linux operating system is an important part of software development. In the transplantation of operating system, MIZI company's system boot program VIVI is used. This program is specially developed for S3C2410 and S3C2440 series microprocessors and is very convenient to use. The transplanted kernel is Linux2.6.12 version, and then the root file system is built to determine the attachment of application programs or other software.

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The above are some software developments for the microprocessor S3C2440A, but the embedded system is a thing with strong real-time operability, especially in some specific product designs, some problems are prone to occur. The root of these problems often appears in the timing problem. Based on this consideration, embedded systems often have to introduce CPLD to coordinate the timing problems of the microprocessor and other peripheral circuits or devices.
3.2 Software Development of XL95144XL
XL95144XL is a widely used CPLD. There are two main programming languages ​​for CPLD: VHDL and Verilog HDL. Here, VHDL language is used to implement programming of XL95144XL. VHDL language is a standard hardware description language for description, simulation, synthesis, optimization and wiring. It has strong transplantation capabilities. It can be transplanted from one simulator to another, from one synthesizer to another, or from one work platform to another.
In this bank evaluator software, CPLD implements two main functions: one is the address allocation function of peripheral devices, which realizes the correct address connection between peripheral devices and S3C2440A; the second is to coordinate the timing or synchronization signal so that the relevant peripheral devices can work normally. It is very easy and convenient for XL95144XL to implement these two functions. Although the amount of program is not large, it plays a great role.
For example, a TFT LCD screen is selected for image display. This screen has strict requirements on the timing of line scanning signals and frame scanning, as shown in Figure 6. If there is a certain timing deviation, it is easy to have a local "flower screen" phenomenon, and the timing of the scanning signal given by the microprocessor S3C2440A after working does not fully meet the index parameters of the LCD screen, as shown in Figure 7. Therefore, it is necessary to coordinate and control the scanning signal through CPLD programming.

As can be seen from Figures 6 and 7, the timing of the scan signal cannot guarantee consistency, which is bound to bring some defects in product design. Some problems will even be reflected very intuitively. This is one of the important reasons for adding CPLD to the embedded system.
3.3 Download and debug
After the software is written, it is necessary to download it. ARM and CPLD have their own JTAG download ports, which are connected to the communication port of the PC through different download lines, and then use the hyperterminal on the PC to download the corresponding software packages to the target board for operation and debugging.

4 Conclusion
The bank evaluator in this article is developed and designed based on embedded systems. Compared with the previous digital tube evaluator with digital display mode, its visual effect has a qualitative leap; furthermore, it also cancels the digital key-type evaluation method and uses a touch screen for customer service evaluation, which has a better effect. At the same time, when customer service operations are not required, other auxiliary software can also be run, which plays the role of a propaganda machine to a certain extent. It can be seen that such a bank evaluator designed based on ARM is powerful
, easy to expand, and has better performance. Moreover, with the development of the electronics industry, the application of embedded systems is becoming more and more extensive. It has become an inevitable trend to use evaluators developed and designed by ARM to replace traditional digital tube evaluators.