Application of embedded extended technology system to logistics inventory PDA wireless terminal design plan detailed

The advancement of science and technology has brought about tremendous changes in the logistics industry, from mechanization to automation and intelligence. my country's logistics industry started late, and it is still in a state of manual management or semi-automatic management, and the efficiency is not high. With the development of the logistics industry, the scale of warehousing continues to expand, and the types of goods continue to increase, which brings a series of chain reactions, which makes the traditional logistics industry increasingly difficult.

The development of embedded expansion technology can provide powerful and flexible solutions for the logistics MA control field. The research scheme of this paper applies the embedded extended technology system to the field of logistics control, adopts embedded processor and abundant peripheral extension interfaces, coupled with LCD touch screen, to realize human-computer interaction. Combine the barcode collector to realize real-time collection of data information, real-time connection to the server database through wireless transmission; real-time inventory of goods, in and out of the warehouse; real-time query information and timely dispatch; also has the ability to store voice data, simple and fast, avoid human error, streamline manpower, and manage inventory , Shorten complicated procedures, save time, improve service quality and other features.

1 System hardware design

1.1 Hardware system composition

The target hardware platform is mainly divided into three parts: the processor core, the peripheral circuits in the chip, and the board-level peripheral circuits. This system mainly includes ARM processor, memory, barcode scanner, wireless transceiver chip, LCD display and touch screen. Its structure diagram is shown as in Fig. 1.

1.2 Selection of main hardware and circuit design

1.2.1 Embedded Processor

This system uses Samsung’s S3C44BOX processor, which is a cost-effective microprocessor specially designed for handheld devices and general applications. It uses an ARM7TDMI core and works at 66MHz. The chip contains very rich on-chip resources, almost all commonly used chip-level bus structures have corresponding hardware controllers, and peripheral expansion is very convenient.

1.2.2 External memory

In order to meet the application needs of logistics PDA, this system uses Flash, SDRAM, and NANDFalsh memory.

The main feature of flash memory (FlashMemory) is to save information when power is off. It not only has the characteristics of ROM, but also has high access speed, easy to erase and rewrite, and low power consumption. In the system, it is usually used to store the operating system and program code, as well as some user data that needs to be saved after the system is powered off [2]. After the system is powered on or reset, it obtains the first instruction and starts to execute it. This system selects a 16bit AM29LV160B linear Flash memory with a single-chip storage capacity of 2MB. Flash and S3C44BOX are connected to the chip selection terminal nGCS0 through a resistor, and an external pull-up resistor is connected; the data line is connected to the address line respectively; the read and write terminals are connected to nOE and nWE respectively.

SDRAM has the characteristics of large storage capacity, low price, and no storage after power failure. This system is mainly used to store running programs and data stacks. This system uses the 57V series HY57V641620 of Hyundai Company, which is a 4Banks×1M&TImes;16bit SDRAM chip, and the single-chip storage capacity is 4 groups&TImes;16MbTI (8MB). In order to meet the needs of complex logistics data information systems and give full play to the data processing capabilities of 32-bit CPUs, the system uses two 8ns HY57V641620s in parallel to form a 32bitSDRAM memory system [3]. Through nSCS strobe, nSRAS, nSCAS to strobe row address and column address addressing respectively.

NANDFlash is cheap, has a large storage capacity, is cost-effective, and is very portable and has good shock resistance, making it suitable for digital products. This article uses K9F2808U0B16M&TImes; 8-bit memory chip with a voltage range of 2.7V～3.6V. When the USB control chip is in SLAVE mode, you can download files from the PC and store them in NANDFlash. When the inventory staff takes the PDA to take inventory, the system can directly call the stored data files. When the inventory staff is finished, they can also keep a copy of the data in NANDFlash for inquiries at any time, and can also save voice data. NANDFlash is strobed through GPC15, and the corresponding nOE and nWE are read and written. The connection circuit diagram of each memory and processor is shown as in Fig. 2.

1.2.3 LCD liquid crystal display and touch screen module

The ARM processor S3C44BOX includes an LCD controller, which can support grayscale LCD and color LCD. This design controls the LCD pixel output and control signal through the decoder strobe 2 74HC245 respectively. This article selects the TFT color 3.9-inch display LQ039Q2DS54 and ADS7843 touch screen driver chip with a resolution of 320×240. S3C44BOX performs data transmission with the touch screen control chip ADS7843 through the port PG analog serial SIO interface, and completes the reading of the touch position coordinates of the touch screen. ADS7843 mainly completes the switching of the electrode voltage, the collection of the voltage value at the contact point and the A/D conversion [4]. The interface circuit diagram is shown as in Fig. 3.

1.2.4 Interface design

(1) RS232 interface design

Since S3C44BOX only has 2 channels of UART and does not integrate RS-232C interface, MAX202 is selected as the level conversion chip from UART to RS-232C, so that it can communicate with other devices such as PC and get data and voice information, which is convenient update data. Choose a 9-pin DB9 header and use 3 wires: GND, RXD, TXD.

(2) JTAG interface

Because the JTAG signal is integrated in the S3C44BOX, the device can be debugged only by pulling out the signal line.

(3) Audio interface design

In order to store the voice information, the UDA1314 chip of Philips is selected to complete the analog-to-digital conversion of the voice signal. The chip integrates a stereo analog-to-digital converter and a digital-to-analog converter on a single chip. The analog-to-digital conversion part of the chip includes a programmable gain amplifier and a digital automatic gain controller, and uses bit stream conversion technology for signal processing. In view of its low power consumption and low voltage characteristics, UDA1341TS is very suitable for portable devices such as PDAs.

(4) USB interface design

The USB interface is a new-generation standard interface bus with low cost, small footprint, unified interface specifications, fast, two-way sharing, and plug-and-play. It is widely used in embedded system devices. The CH372 chip used in this article is a universal device interface device for the USB bus. At the local end, it has an 8-bit data bus, read, write, chip select control lines, and interrupt output, which can be easily connected to the system bus of the single-chip microcomputer. In the computer system, the CH372 supporting software provides a concise and easy-to-use operation interface, communicating with the local MCU is just like reading and writing files. CH372 has built-in the bottom layer protocol in USB communication, has the trouble-saving built-in firmware mode and flexible external firmware mode. In the built-in firmware mode, CH372 automatically handles all transactions of the default endpoint O, and the local end is only responsible for data exchange, so the program is very concise. In the external firmware mode, the external one-chip computer processes various USB requests on its own according to needs, so as to realize devices that conform to various USB specifications [5].

Through the combination of a USB interface and a micro bar code scanner with a USB interface, you can easily connect to a PDA to collect data on logistics goods. Make logistics data collection easy and fast. The interface design circuit diagram is shown as in Fig. 4.

1.2.5 Design of wireless communication module

A wireless transceiver module with 2.4GHz wireless transceiver nRF2401 and enhanced 8051 core is selected. The nRF24E1 is small in size and low in power consumption. It is a highly integrated chip that integrates wireless transceiver, 8051, ADC and other peripheral devices. It contains 125 frequency points, which can realize point-to-point and point-to-multipoint wireless communication. At the same time, frequency change and frequency hopping can be used to avoid interference. The maximum transmission rate of nRF24E1 can reach 1M/s, and its maximum transmission power is 0dBm. In an ideal environment, its indoor transmission distance can reach 30m～40m, and the outdoor transmission distance can reach 100m～200m. The circuit diagram is shown in 5.

The data obtained from the barcode scanner is transmitted to the nRF2401 through the processor, and then wirelessly transmitted to the AP (wireless access point), and then transmitted to the background computer database through the AP, so that the field and the background data are correlated to obtain the correct real-time data. Efficiently and easily realize the statistical inquiry of logistics inventory, warehouse entry and exit, and supply information.

2 Software design

The operating system core of the lower computer is the S3C44BOX operating system, which adopts the Linux kernel, initializes the hardware through Bootloader, and boots the kernel and file system to start the Linux system. The software design is as follows:

(1) Design and implementation of Bootloader. Bootloader is the first piece of code executed before entering the operating system after the processor is reset, loading and booting the entire system. Divided into 2 stages, the first stage is mainly related to CPU core and memory processing and initialization work, this part is mainly in Flash. The second stage mainly realizes the support of general process and peripheral expansion, which can streamline unnecessary drivers and reduce the kernel running space.

(2) Linux kernel transplantation. Modify the main register by modifying the kernel's startup code, processor system and structure. The common startup parameters that usually need to be set by the Bootloader are: ATAG_CORE, ATAG_MEM, ATAG_CMDLINE, ATAG_RAMDISK, ATAG_INITRD, etc. Add the compilation support of the development board through arch/arm/makefile to generate kernel images and modules; modify the initialization code and entry through cpu/mips/start.s; initialize the assembly code of the hardware through board/myboard/lowlevel_init.s; through include/ configs/drivers implements the modification of device drivers [6].

(3) File system migration. Use nfs as the root file system.

(4) Application programming. Design and develop user graphical interface through Qt/Embeded.

The birth of the embedded mobile wireless PDA terminal improves the complexity of logistics inventory and the real-time performance of data, making scheduling and management more accurate. In this paper, the barcode scanner and mobile PDA are cleverly combined to realize a mobile terminal that integrates data collection, data processing, data display, data modification and other functions. Compared with other equipment, this article has the characteristics of logistics-oriented, simple, compact, powerful, can collect data, transmit data, query data anytime and anywhere, and can also store voice data, etc., so that logistics data can be real-time, dispatched in time, and errors are reduced. Manpower and material resources are diminishing.

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