System design of anti-collision wireless communication car black box

Car driving recorder (commonly known as car black box) is a digital electronic recording device that records and stores the driving speed, time, mileage and other status information about the driving of the vehicle and can output data through the interface. It plays an important role in suppressing traffic violations such as fatigue driving and vehicle speeding, restricting bad driving behaviors of drivers, ensuring vehicle driving safety, and analyzing and appraising road traffic accidents.

In recent years, some domestic provinces have stipulated that long-distance passenger vehicles must be installed with a car driving recorder. In this paper, according to the national standard GB / T 19056-2003 of the vehicle traveling data recorder, a design that complies with the national standard and adds the function of wireless data upload for collision prevention in the existing vehicle traveling data recorder products is added. The following mainly describes the basic functions of the car driving recorder and the design of the hardware architecture and software system.

1 Basic functions of car driving recorder

The national standard GB / T 19056-2003 mainly requires the recorder to have the following functions:

(1) Self-check function

When the recorder starts to work after power-on, it should first perform a self-test. After the self-test is normal, it should be indicated by the green flashing signal and the display mode of the display to work normally.

(2) Driver identity record function

Each recorder is equipped with a unique serial number, and is installed with a non-contact RF IC card verification machine, or key person password mode, users can use IC card mode or type the password mode to verify the identity of the driver as needed. If the identity verification is not performed before driving, or the identity verification is invalid, the default is the last driver identity. The driver's identity verification data can be conveniently viewed through the recorder management software. If the driver's identity verification is invalid, it does not affect driving, but the relevant data of illegal driving can be viewed through the management software.

(3) Data display

Speed ​​detection is synchronized with the vehicle speed meter, digital display, detection accuracy is ± 50 r / min, display range is 0 ~ 9 999 r / m. The engine speed characteristic coefficient can be set through the recorder management software.

Date and time record format: Beijing time * year * month * day * hour * minute * second, relative error: ± 5 s.

(4) Data collection, recording and storage functions

It can measure, record, and store data such as time, date, driving time, vehicle speed, and mileage in real time, and ensure that the stored data is not lost for a long time. The input signals that need to be collected include three types: analog signal input, digital signal input, and digital signal input.

(5) Data communication function

The recorder can communicate with the external environment through multiple methods (including RS 232 serial interface, USB interface and I2C bus interface) to achieve data interaction.

Most of the data upload of the existing car driving recorder is wired transmission, such as USB, serial cable transmission, etc. In situations where wired transmission cannot be used, it is a more reasonable solution to use a wireless data transmission module and a single-chip microcomputer for data transmission. This article is to use LPC2214 and SR-WF-1021 digital transmission module combination, plus a simple anti-collision algorithm for data communication.

(6) Alarm and record of speeding and driver fatigue driving

When the vehicle speed exceeds the set limit (can be set according to user needs), the recorder will sound and light alarm to remind the driver to slow down. The alarm sound interval is 4s.

When the same driver has been driving continuously for more than 4 h, the recorder will record the relevant data of the driver's fatigue driving and issue a buzzer alarm. At the same time, the red light flashes, similar to the speeding alarm. When the continuous driving stops for more than 20 minutes, the recorder automatically releases the accumulation of the current fatigue time. If the parking time is less than 20 min, the recorder is still regarded as continuous driving, accumulating fatigue driving time.

2 System hardware design

This paper designs a simplified embedded wireless data acquisition system based on the LPC2214 microcontroller, the system block diagram shown in Figure 1. The system is small in size, light in weight, low in operating cost, and relies on the existing wireless module self-organizing network to customize the communication protocol. It is especially suitable for the occasions with wide distribution range, large number of collection points, and automatic duty.

The host part of the system includes: signal input, data storage and processing, data display, data communication, reset circuit and power-off protection circuit and other parts.

System Block Diagram

Real-time clock circuit, in the event of violations such as speeding and fatigue driving, LPC2214 can directly read real-time time from the real-time clock circuit for processing and saving.

The system has a USB interface. When the user inserts a USB disk, the USB function can be used to import the data in the memory into the disk. The host computer software can use the data collected by this USB disk for data analysis and vehicle and personnel management.

The reset circuit can not only reset the system, but also can deal with the crash caused by wireless communication jamming caused by some interference signals in the wireless communication. At the same time, the power monitoring chip in the LPC2214 can improve the reliability of the system, thus ensuring that the LPC2214 has many aspects such as power supply and clock source Higher requirements.

2.1 CPU module

The CPU module in the system is a high-speed processor LPC2214 based on a 32-bit ARM7TDMISTM CPU that supports real-time simulation and tracking.

LPC2214 has 256 KB embedded high-speed FLASH memory. The 128-bit wide memory interface and unique acceleration structure enable 32-bit code to run at the maximum clock rate. Applications with strict code size control can use the 16-bit Thumb mode to reduce the code size by more than 30%, but the performance loss is very small.

The LPC2214 is packaged in 144 pins and can use up to 76 GPIOs (using external memory) to 112 (single-chip applications). Due to the built-in wide range of serial communication interfaces, they are very suitable for communication gateways, protocol converters, embedded soft Modern and other various types of applications.

2.2 Data collection

In this paper, the analog quantity acquisition is to directly use the existing successive approximation 10 b A / D converter in the LPC2214 to achieve 8-channel rapid analog signal acquisition. The measurement range of the converter is 0 ~ 3 V, the fastest conversion speed can reach 2.44μs / time, programming is simple, and the required function can also be selected to improve the conversion accuracy of the converter.

In this paper, the switch quantity is collected by 8-channel switch quantity. After the external switch signal passes through the photoelectric isolation TLP421, it is introduced into the system from the 8 I / O ports of the LPC2214, and the 8-channel switch signal is interrupted or queried by programming. collection.

DELL Latitude 3120 E3120

Dell latitude 3120; Dell 3120; Dell 3120 parts; Dell 3120 lcd; Dell 3120 keyboard; dell 3120 laptop

S-yuan Electronic Technology Limited , https://www.syuanelectronic.com

Posted on