With the development of society, my country's aging population more and more serious, for the care of the elderly has become a social problem. Based on the demand characteristics of elderly care, the use of our self-developed Beidou satellite positioning system, combined with the Beidou positioning module BDM100 designed two different programs for home care end demand for real-time positioning for the elderly, and real-time location information transmission into the hands of regulators. The first embodiment uses EVDO 3G network support module MC8630, is joined to ARM9 core chip AT91SAM9260 return position information, the transmission scheme having fast, scalable characteristics, information can be passed after the body, environment information room for expansion. The second implementation uses the GSM module supports the 2G network GTM900, combined in Cortex-M3 LPC1766 chip as the core positioning information transmission, the software program combines good design, low cost and stable performance characteristics. After experimental testing, these two programs can be a good solution to the problem of domestic real-time location monitoring in the elderly.
1 BDM100 module design
BDM100 module is a dual system GNSS performance module can support BD2 B1, GPS L1 frequency two, well adapted to low-cost, low-power field, can be large-scale system integration Compass. Module block diagram is shown below:
1 BDM100 module block diagram of FIG.
It can be seen from the block diagram chips, BDM100 support UART, SPI, 1PPS, I2C and other interfaces. Which can correlators, FFT, and mixing applications and a matched filter algorithm optimized to maintain good tracking and capture fast TTFF functions in various complex environments. Multi-path mitigation technology and high quality raw data, can guarantee a good timing, the accuracy of navigation. BDM100 system for a hybrid multi-chip may be positioned, which can improve the positioning accuracy, because this paper Beidou system, so that only select Beidou function. Further, BDM100 chip has three serial ports, the user can set the baud rate, the baud rate is 9600 by default, and may be firmware upgrade through the serial port 3. Positioning accuracy of the module up to 3 meters, the measurement precision can reach 0.1 m / sec. Application of the peripheral circuit diagram of the present system used is as follows:
2 BDM100 circuit diagram of a peripheral module
Present two systems are using a serial communication with the MCU, a serial interface for 3 Reserved for future upgrades. Special Note: When the module starts normally, the reset signal within the validity period, to keep the serial input pin 3 constant level is high, otherwise the module will enter the firmware upgrade mode, unable to start properly. Module reset signal is active low, and the duration of not less than 2 ms; this module must be equipped with an antenna + 2.85V active antenna, the antenna connected to GNSS_ANT pin, the internal active antenna modules integrated LNA (low noise amplifier) , can be directly connected to the module pin GNSS_ANT, the use of a non-+ 2.85V active antenna, the antenna power is required.
As used herein, the software module BDM100 interface protocol which uses mainly accomplished by passing the message transmitting information, wherein "message" is a code string composed of full ASCLL. The basic format of the message is:
Table 1 BDM100 message format module
In which all messages are to $ (0x24) to start, followed by the message name, and then followed by a variable number of parameters or data. Are comma (0x2C) separated between the data and the message name. Represents the input message can (0x0A) or ends with '\ r' (0x0D) or '\ n' of any combination of the two, and represents the output of the message to all the combinations of '\ r \ n' ends. Message name and parameters are case insensitive.
BDM100 module needs to be initialized prior to use, the process is the initialization process message interaction between the module and the master chip. BDM100 module having a positioning and timing functions, the present system uses only its positioning function, so will not be described for the timing function during initialization.
Initialization command need to use this system as follows:
Table 2 BDM100 initialization command module
Since in the embodiment wherein the 3G communication using the USB interface, it is necessary to set the baud rate 115200 (default 9600 baud), the specific command: $ CFGPRT, 3, h0,115200,3,3. Since this system is used Beidou system, the GPS module can support BDM100 Compass and hybrid positioning, it is necessary upon initialization module for Beidou mode, two commands can be used to achieve -CFGSYS / CFGNAV, specifically command: $ CFGSYS, h10 or $ CFGNAV, 1000,1000,3,2. For a variety of output messages, specific coding table below:
Table 3 BDM100 message type list module
The system used in the output required location information and corresponding time information, from the above it can be seen using the message type RMC GLL message or messages are to meet the requirements, because the message is shorter than the RMC GLL message, the information is relatively high efficiency, so the system employed in the design GLL message transmitted. Processing power factor control scheme in connection restriction, GLL message needs to set its output frequency is 1 time / second, and the category and its corresponding ID number are 0 and 1, that GLL message by looking up the corresponding chip Software Manual output frequency is 1Hz, so the use of the frequency CFGMSG provided with specific instructions to: $ CFGMSG, 0,0,1.
When the above process is completed, we need to save the settings, use the command is: $ CFGSAVE.
After initialization is complete, BDM100 chip will be at a rate of 1 / sec data output outward through the interface, and receives and processes linked thereto by the master chip process.
2 3G Design and Implementation
3G employed to design a monitoring terminal ARM926EJ-S AT91SAM9260 chip as the core as the master chip, the chip has a stable, rich peripheral interfaces, embedded Ethernet, with fast RAM and ROM, LINUX operating system support features. Message backhaul 3G chip module MC8630,3G EVDO network services require high data throughput with, so the data EVDO module supports CDMA2000 packet service provided by China Telecom, for wireless data access services, access speeds close to EVDO ADSL Internet limited level, and the use of this embodiment, stable data transfer, leaving space for future expansion properties, meet the design requirements.
2.1 Hardware Design
3G embodiment of hardware connection diagram as follows:
3 3G plan diagram of FIG.
Wherein the AT91SAM9260 BDM100 modules and master chip, and the chip MC8630 3G via UART interface control chip through the USB port, so that to ensure the stability of the receive and transmit at the same time, can also provide space for future expansion properties. DETAILED BDM100 connection module and the circuit shown in Figure 2 of the master chip, while the 3G module and the master chip is connected below:
FIG 4 3G module and a master chip connected FIG.
2.2 Software Design
On the master chip using AT91SAM9260 linux operating system as the operating system has been used in many embedded devices above, its stability has been demonstrated.
2.2.1 BDM100 connection module
BDM100 modules and UART serial communication controller chips, after completing arranged in the linux kernel, using serial communication interface transmits positioning information and initialization. In the present embodiment, the specific serial communication function is as follows:
During serial communication, the serial port first initialized, the corresponding function is executed Serial_init.
The specific format:
int serial_init (char * dev, int speed, int is_block)
Where dev is the device file address, speed serial port baud rate, is_block is set at initialization is not successful, whether the block until initialization is successful.
Initialization function by calling the static int open_dev (char * dev, int is_block) function to open the device file, which is consistent meaning dev and is_block parameters and initialization function. Open succeeded, the device returns a file descriptor, otherwise -1. Baud rate is set by calling the static void set_speed (int fd, int speed), which represents a device descriptor fd, Speed indicates the rate, when this function is called, to serial stop working.
After initialization is complete, data can be written and read, read function:
int serial_read_timeout (int fd, char * str, unsigned int len, unsigned int timeout / * ms * /)
This is the serial port read function with a timeout mechanisms, the received data in the string str, FD indicates the device address of the file, len indicates the length of the read, timeout denotes the length of the timeout time, ms level, the read function returns .
The so-called time-out mechanism, the program refers to the use of this function to read the data, it will start a thread, run-time data, no data is blocked, when the thread has data, read data, programs, and then continue, if the timeout has not read finished, then give up reading, the program continues, usually within the set time, the program can read the data, this is done to prevent the thread deadlock can not be the end of the thread.
Serial port as a function of the specific format:
int serial_send (int fd, char * str, unsigned int len)
Where fd denotes the device file address, the transmission data is placed in str, len length. Length transmission sent successfully returned, otherwise the return value is less than zero.
By such three functions, can communicate with the master chip module BDM100 AT91SAM9260, the initialization operation can be completed transmission module and related information.
2.2.2 MC8630 connection module
EVDO RF module used in the present embodiment, initially unrecognizable
Our other product:
