Embedded System Design Based on ARM

Today's society is a highly information-based and networked society. Computers and networks have fully penetrated into every corner of daily life. The information age and digital age have brought huge development opportunities to embedded products. Embedded systems are widely used, and military defense is an important application field of embedded systems. Embedded systems can be seen in various weapon controls such as artillery control, missile control, and smart bomb guidance and detonation control, as well as tanks, ships, bombers, various military electronic equipment for land, sea and air, radars, electronic countermeasures, military communication equipment, and field command and operations.

1 System Overview

1.1 System Structure

This system consists of ARM board, ADU3600 board, display, motherboard, etc.

1.2 ARM Processor Features

The ARM (Advanced RISC Machine) microprocessor architecture is currently recognized as the leading 32-bit embedded RISC microprocessor structure in the field of embedded applications. It uses a 32-bit address and data bus, and its address space reaches 232=4GB. It has the characteristics of low power consumption, high cost performance and high code density. It uses a large number of registers, most data operations are completed in registers, and the instruction execution speed is faster. The addressing method is flexible and simple, and the execution efficiency is high.

1.3 ADU3600 Board Features

It overcomes the defect of inertial orientation product accuracy drifting with time and temperature, and uses carrier measurement technology and fast integer ambiguity solution technology to calculate the positions of the two GPS receiver antennas and the angle between the line connecting the phase centers of the two antennas and the true north.

2 System Hardware Design

2.1 Data receiving circuit

The selected GPS antenna is a zero-phase measurement antenna, and the feeder and antenna are well matched with the standard antenna in terms of impedance, gain, and amplification factor.

Front antenna: Connect one end of the antenna feeder to the interface and the other end to the GPS front antenna (forward direction).

Rear antenna: Connect one end of the antenna feeder to the interface and the other end to the GPS rear antenna (backward direction).

The line from the phase center of the GPS rear antenna to the phase center of the GPS front antenna is called the baseline. The angle between the baseline and the true north is called the azimuth. The longer the baseline, the higher the heading accuracy. Generally, doubling the baseline length will double the heading accuracy. The distance between the two antennas should be as long as possible to improve the heading accuracy.

2.2 Data Processing Circuit

After receiving the data through the two GPS antennas, the receiving board performs the first data processing, classification, and packaging, and then transmits the processed data to the main board through the serial port. After the main board receives the data, it performs a series of tasks such as the second data processing, classification, and packaging, and finally displays the corresponding data on the display screen, and at the same time sends the data to the peripherals through the serial port through the motherboard. [page]

2.3 Interface Circuit

(1) Display interface

Liquid crystal displays (LCDs) are widely used in embedded systems due to their low power consumption and small size. LCD displays achieve display purposes by supplying power to different liquid crystal units and controlling the passage of light.

(2) Serial interface

The RS-232C used in this system is a serial communication interface standard developed and adopted by the American Electronics Industry Association (EIA), and has developed into an internationally used serial communication interface standard.

3 System Software Design

Embedded software can be divided into three categories: system software, application software and support software. System software controls and manages embedded system resources and provides various software that supports embedded applications, such as device drivers, embedded operating systems, etc. Application software is the upper-level software in the embedded system, which defines the main functions and uses of embedded devices and is responsible for interacting with users; support software is tool software that assists software development, such as cross compilers, online simulation tools, etc. In this system, the system software and application software run on embedded devices, and the support software runs on ordinary PCs.

3.1 Board Support Package

The device driver layer is also called the Board Support Package (BSP), which contains all the hardware-related codes in the embedded system and provides a virtual hardware platform for the operating system to run on. It includes the boot loader and the device driver. The boot loader is a small program that runs before the operating system kernel runs. Through this program, we can initialize the hardware device, establish a mapping of the memory space, and set the system's hardware and software environment to a suitable state to prepare for the final call to the operating system kernel; the device driver is a set of library functions used to initialize and manage the hardware. And provide a good access interface to the upper-level software.

3.2 Embedded Operating System (EOS)

VxWorks used in this system is an embedded real-time operating system developed by WindRiver System of the United States. It has good reliability and excellent real-time performance. It is the most widely used commercial system with the highest market share in the field of embedded systems. It is based on the microkernel architecture, uses GNU type compiler and debugger, and most API functions are proprietary.

3.3 Integrated Development Environment

Tornado is an integrated development environment launched by WindRiver.

3.4 Application Software

The system program is written in standard C language, debugged in Tornado integrated development environment, transmitted and loaded into ARM board through serial port or network communication line, and finally runs independently in ARM board without host computer.

4 System Performance Indicators

(1) The positioning error is no more than 30 m, and the orientation error is no more than 0.06°;

(2) Positioning and orientation should not exceed 2 minutes;

(3) EL display readable in sunlight;

(4) The total power does not exceed 10 W;

(5) The volume of the packaging box shall not exceed 410 mm × 322 mm × 216 mm, and the mass shall not exceed 20 kg;

(6) Suitable for working at -40℃~50℃ and suitable for storage at -55℃~60℃.

5 Conclusion

The hardware design of this system is based on comprehensive consideration of the hardware platform, embedded processor, peripheral devices, and interface circuits, and the hardware stability and reliability requirements have been met after testing; in the software design, the real-time and scalability of the system are fully considered in the selection of embedded platform, operating system, programming language, and integrated development environment.