Application of GPS global positioning technology in medical monitoring equipment

summary

This paper discusses the application of GPS global positioning technology in medical monitoring and prepares a GPS medical monitoring positioning device, which is mainly composed of a single-chip control module and a GPS receiving module. It has the advantages of high accuracy, good stability, strong anti-attenuation ability and low power consumption, and realizes outdoor care.

1. Introduction

At present, there are about 300 million people in need of care in my country, mainly children and elderly patients. Due to the intense pace of modern life and parents being busy with work, children have more free space to move around, and children are often found to be lost or injured; patients in hospitals, such as those with Alzheimer's disease, also get lost. How to monitor this group at any time has become a problem that caregivers are very concerned about and eager to solve.

GPS (Global Positioning System)[1] was developed by the United States in the 1970s. It took 20 years and cost $20 billion to complete in 1994. It is a satellite system capable of all-round real-time three-dimensional navigation and positioning at sea, land and air. It has the characteristics of good performance, high accuracy and wide application. It is now open to use for free and is the best navigation and positioning system to date. With the continuous improvement of the global positioning system and the continuous improvement of hardware and software, the application field is constantly expanding. It has now spread to various sectors of the national economy and has gradually penetrated into people's daily lives. We use GPS technology to prepare positioning devices for monitoring to meet the real-time care of children by families and patients by hospitals, so as to reassure parents at work, prevent patients from getting lost in hospitals, improve the level of care for patients in hospitals, and expand the range of patients' activities.

2. Device hardware design and implementation

The medical monitoring device (Figure 1) consists of two parts: a single-chip control module and a GPS receiving module. The two modules exchange information through a serial port mechanism.

Figure 1 Medical monitoring device system structure

2.1 Single chip microcomputer control module (Figure 2):

By expanding the peripheral circuit, we can realize the collection of physiological parameter data, keyboard operation, physiological parameter LCD display and automatic alarm. We use G191 LCD module, 192×128 dot matrix, dot size is 0.33×0.33mm, dot pitch is 0.04mm, driving power supply is +5V and -20V. We use SED1335 as LCD controller, which is used to receive various instructions and data from the control module, generate corresponding timing to control the LCD screen display. SED1335 has very powerful software functions, and comes with data RAM, and can manage the display buffer area by itself, which is convenient for us to use.

Figure 2 MCU control module circuit

2.2 GPS receiving module:

Responsible for receiving information from GPS satellites (space part) and sending data to the single-chip control module through the UART serial port in real time. During the design process, through analysis and comparison, we chose the GR-85 serial port GPS receiver from Taiwan HOLUX Company. In terms of signal capture and signal accuracy, GR-85 has its unique advantages. Its signal recapture time only takes 100ms, and the minimum speed update rate can reach 1s.

The GR-85 receiving module adopts serial communication mode, and its data format is defined as follows: 9600b/s, 8 data bits, 1 stop bit, and non-polarity output. GR-85 supports six NMEA-0183 protocol information: GGA, GLL, GSA, GSV, RMC, and VTG. The difference between these six types of information is that the types of information that users can receive are different. For example, there is speed information in the RMC format, but not in other formats. Designers can choose the corresponding information format as needed. This experiment uses the RMC format. Table 1 shows the pins of the GPS receiving module. The receiving module communicates with the microcontroller mainly through the TXA pin.

Table 1 GPS receiver module pins

3. System software design and implementation

As long as the GPS receiving board is powered on, it will continuously transmit the received and calculated GPS navigation and positioning information to the single-chip microcomputer system through the serial port. To extract GPS information, we must first clarify its frame structure. The data frame is mainly composed of a frame header, a frame footer, and data in the frame. Each frame uses a carriage return character and a line feed character as the frame footer to mark the end of a frame. To process the data frame, we first determine the frame header and then extract the data from the required frame. Since each data segment in the frame is separated by a comma, when processing the received data, we generally first determine whether it is a frame header by searching for the ASCII code of "$", then identify the type of the frame header, and then determine which parameter is currently being read based on the identified frame type and the number of commas ',', and make corresponding extraction and storage. We use interruption to obtain GPS data.

In order to store the received and processed time and longitude and latitude data, we have allocated a fixed space in the memory. 3BH-5FH is used to store the received time and longitude and latitude data, and 6BH-7FH is used to store the processed time and longitude and latitude data.

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The system flow chart is shown in Figure 3:

Figure 3 System flow chart

3.1 The GPS data output format is as follows:

$GPRMC,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>*hh
The format is as follows: <1> Greenwich Mean Time of the current position, in the format of hhmmss; <2> Status, A is a valid position, V is an invalid reception warning, that is, the number of satellites above the current antenna field of view is less than 3; <3> Latitude, in the format of ddmm.mmmm; <4> Indicates the northern and southern hemispheres, N is the northern hemisphere, S is the southern hemisphere; <5> Longitude, in the format of dddmm.mmmm; <6> Indicates the eastern and western hemispheres, E is the eastern hemisphere, W is the western hemisphere; <7> The moving speed of the GPS receiver on the ground; <8> Azimuth, in the range of 000.0 to 359.9; <9> Date, The format is ddmmyy; <10> geomagnetic change; <11> direction of geomagnetic change, which can be E or W.

Output example:

$GPRMC,161229.487,A,3723.2475,N,12158.3416,W,0.13,309.62,120598, ,*10

3.2 GPS information receiving procedure:

Interrupt receiving procedure

XINTS:MOV A,SBUF

JB DFLAG,DF

JB CFLAG,CF

JB MFLAG, MF

JB RFLAG,RF

JB PFLAG,PF

JB G1FLAG,G1F

JB SFLAG,SF

XRL A,#24H

JZ SYES

MOV 20H,#00H; if not, clear all flags

LJMP INTSOUT

SYES:SETB SFLAG; yes $, set flag

LJMP INTSOUT

SF: XRL A,#47H; is it the first G?

JZ G1YES; yes G to G1TES

MOV 20H,#00H

LJMP INTSOUT

G1YES:SETB G1FLAG

INTSOUT:POP ACC

RETI

G1F: XRL A,#50H;Is it P?

JZ PYES; if yes, switch to PYES

MOV 20H,#00H

LJMP INTSOUT

PYES:SETB PFLAG

LJMP INTSOUT

PF:XRL A,#52H;Is it R?

JZ RYES; if yes, change to RYES

MOV 20H,#00H

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LJMP INTSOUT

RYES:SETB RFLAG

LJMP INTSOUT

RF:XRL A,#4DH;Is it M?

JZ MYES; if yes, transfer to MYES

MOV 20H,#00H

LJMP INTSOUT

MYES: SETB MFLAG

LJMP INTSOUT

MF: XRL A,#43H; is it C?

JZ CYES; is transferred to CYES

MOV 20H,#00H

LJMP INTSOUT

CYES: SETB CFLAG

LJMP INTSOUT

CF:XRL A,#2CH

JZ DYES

MOV 20H,#00H

LJMP INTSOUT

DYES:SETB DFLAG

LJMP INTSOUT

DF:MOV @R0,A

DEC R0

DJNZ R3,INTSOUT

MOV R3,#25H

MOV R0,#3bH

LJMP INTSOUT

4. Results and Discussion

After experimental testing, the system error is within 5 meters. When measured in different geographical locations and weather conditions in Guangzhou, the system can locate the target. The system refreshes data every 5 seconds, reducing the system unit power consumption to 1/4 of the power consumption of continuous testing. At the same time, compared with the use of infrared and radio frequency technology for positioning and ranging, this system has higher accuracy, stability and anti-attenuation ability, which is conducive to information transmission during monitoring.

Experiments have proved that it is feasible to use GPS technology to monitor patients and children in outdoor activities. The system can be used to monitor the monitored objects in real time. Once the patient is in a critical condition, the patient's location can be known through GPS information, thereby greatly improving the efficiency of rescuing the patient. Lost children and Alzheimer's patients can also be found in time. At the same time, the device can also be used for positioning and tracking of outdoor activities such as tourism and exploration.

There have been relevant reports on the application of GPS technology in the fields of military, transportation, and field geological prospecting [2-4], but there have been no detailed reports on the application of GPS technology in medical monitoring. The author of this article has made innovations: specifically explored the technical issues of applying GPS technology to medical monitoring positioning, expanded the scope of application of GPS technology, and realized a new medical monitoring positioning technology. Due to the free use of GPS technology and the high accuracy, good stability, strong anti-attenuation ability, and low power consumption of the GPS medical monitoring positioning device, the GPS medical monitoring positioning device has a good application prospect in medical care.

References:

1. Liu Jiyu, Principles and Methods of GPS Satellite Navigation Positioning [M], Beijing: Science Press, 2003

2. He Xiangling, Zhang Yue, Zheng Gang, et al., The current status, dynamics and applications of GPS global satellite positioning technology, Microcomputer Information, 2002, 18 (5): 3

3. Lu Xiaofeng, Lu Hengli, Zhang Fangqin, Design and application of GPRS and GPS in automobile information service system, Microcomputer Information, 2005, 21 (3): 188

4. Ye Jilong, Gan Yanhui, Ran Jianduojie, Application of GPS in field geological prospecting, Geological and Mineral Surveying, 2006, 22(1): 36-37