Use the S3C2410 design 3-lead ECG Telemonitoring

Mainly introduces an approach based on three-lead S3C2410 platform remote ECG monitoring system.

The system is not affected by time and space constraints on real-time monitoring of heart patients, thereby facilitating patients and healthcare professionals to communicate at any time. After clinical testing by medical experts and heart disease.

1 introduction as the people's living standards, the acceleration of the pace of life, the incidence of cardiovascular diseases increased rapidly, has become a threat to human health is one of the major factors.

The ECG is the treatment of such diseases, principally, a diagnosis of reliable, easy to patients without prejudice, in modern medicine, are becoming increasingly important. Regular ECG is the patient lying by ECG record ECG activities, which lasted only a few s ~ 1 m, only a small amount for cardiac status obtained information, so for a limited time, even if arrhythmia occurs is found, the probability is very low. Therefore necessary to adopt appropriate care unit patients long live monitoring, recording patient ECG data. And since the incidence of heart attack with abrupt, patients could not possibly long lying in the hospital, but also need immediate medical staff care, research and development of the portable wireless ECG monitoring products becomes more important.

Currently, although country forming wireless ECG monitoring products, but its adoption of the programme are "collector + transmitter (PDA or cell phone)," and this will inevitably lead to its expensive, and PDA or cell phone's other features for the vast majority of patients completely unnecessary, so far internally practical wireless ECG monitor products areas or blank.

This remote ECG monitoring system is in the hospital on the basis of the proposal, after full investigation and design of the overall programme, the main achievement of the following features:

3-lead ECG signal acquisition;

Wireless transmission of emergency cases 40 s of ECG data and diagnosis; continuous recording 24 hours ECG; upload via high-speed USB to PC ECG data; emergency calls.

2 system design

As portable handheld remote mobile terminal, at design time should take full account of their small size, low power consumption, storage capacity and processing speeds high demand, so the choice of the CPU very carefully.

After data collection and the repeated comparisons, finally chose the Samsung company launched the S3C2410 ARM920T core-based processors, the processor information-rich, cost-effective.

Use RISC architecture ARM microprocessors generally has the following characteristics:

Small size, low power consumption, low cost, high-performance; support for the Thumb (16 bit)/ARM (32 bit) dual instruction set; significant use of register, so that the instruction execution speed faster; addressing ways to perform simple, flexible and high efficiency; instruction length fixed.

You can see the arm-based embedded processor is a portable handheld Terminal is the best choice, so when you design a system of first positioned on the series processor.

S3C2410 ARM920T processor core-based processors, uses 0.18 μ m manufacturing process 32-bit micro-controller, using the five-stage pipeline Harvard architecture, maximum operating frequency is 203 MHz. The processor has: independent 16-KB instruction Cache and data Cache, MMU 16KB, support for TFT LCD controller, NAND Flash controller, 3-channel UART, 4-channel PWM Timer, rich of I/O ports, 8-channel 10-bit ADC, Touch Screen interface, IICBUS interface, and two USB host and USB device, such as 1 a rich peripheral devices.

S3C2410 provides a more complete common peripherals, and make the whole system of minimum power consumption, thereby eliminating the add and configure additional peripheral interface troubles, effectively reduce the circuit board area, this is exactly the system select the processor.

System's overall structure as shown in Figure 1, the S3C2410, scaling out an 8 MB of NOR FLASH, 64 MB NAND FLASH and 16 MB of SDRAM, memory chips, through GPIO port expanded keyboard, LCD and buzzer, man-machine interface unit, external USB UART, communication interfaces and while connected to a Siemens company-MC35 module for wireless transmission and emergency call capabilities.

From the system's overall function of the structure, the system can be divided into five modules: power module, ECG data acquisition module, data wireless transmission module, graphical user interface modules, data storage management modules.

Figure 1 system architecture

2.1 power module in the original location system adopts single 1700 mAh lithium-ion rechargeable battery, but with the power of the release, the voltage is continuously decreasing, the variation range of 4.2 ~ 2.75 V.

But the system needs a 4.3 V respectively the MC35 operating voltage, an i/o voltage V 3.3, a 1.8 V CPU core voltage and a 1.8 V CPU dedicated voltage. In order to satisfy the system requirements, power circuits must both boost regulator and low-dropout linear regulators. In order to solve the problem system uses 1 switching boost DCDC regulator, 1 3.3 V low-dropout linear regulator and 2 with Shutdown pin 1.8 V low dropout linear regulator to power supply, power supply scheme as shown in Figure 2.

Figure 2 power supply module programme 2.2 ECG data collection in the original position as ECG signal detection is a strong noise subwoofer (0.5 ~ 1

00 Hz) Dim (0.1 ~ 5 mV) signal detection, with a faint resistance, stability, low frequency characteristic and randomness, and other characteristics, they require lead level should meet high input impedance and high common-mode rejection ratio (CMRR), low noise, low drift and high security. Dim ECG from human interference, inside and outside the range of its features are submerged in a complex signal, in order for its features, it is necessary to be preprocessed. The system adopts the principle of ECG collection as shown in Figure 3. Including front-level differential amplifier adopted, its magnification 22.4 times; after amplification circuit magnification of 37 times, total magnification 828.8 times.

Figure 3 ECG collection principle because of the ECG to low-frequency signals in analog circuit design, to 100 Hz cutoff frequency of first-order low-pass filter to filter out high frequency interference, using second-order VCVS band-stop filter to filter out 50 Hz mains frequency interference.

In the digital processing, in order to curb on ECG effects larger frequency interference and baseline drift, with 2 048 point FFT on the input of a frame an ECG data — frequency domain transformation in time domain, and then remove 0.5 Hz low and below 50 Hz mains frequency; at the same time in order to suppress high-frequency noise and 50 Hz frequency disturbance and filter in addition to the frequency of 100 Hz and above, and then will this group data IFFT shift back to the time domain. 2.3 data wireless transmission module in the original location of this system to remote mobile terminals, wireless transmission of data involved, to implement this functionality using a Siemens MC35 module, the company and transfer the TCPIP protocol stack and the PPP protocol, to complete the ECG data of sending and receiving of diagnostic results. Siemens MC35 is the company launched the first support GPRS GSM/GPRS module, its small size, easy to integrate into a portable handheld Terminal, support for VOICE, DATA, FAX and SMS, and other services. Processor S3C2410 asynchronous serial communication interfaces are connected with the MC35, and through the at command to the module for control and data transfer. When sending data, first of all, the application tier will be collected by ECG data submitted to the TCPIP protocol stack; then, TCPIP protocol stack based on the destination address and port to the ECG data package to complete the IP datagram, and then submitted to the PPP layer; Finally, the IP datagram layer via PPP package, through serial byte by byte and submitted to the MC35 and send. When receiving data, the MC35 first receives the data byte by byte and submitted to the PPP layer; the PPP layer will be distributed to each byte of a frame to complete the IP datagram, then submitted to a detailed TCPIP layer, the specific process shown in Figure 4. The initialization to complete the startup and logon MC35 mobile Monternet gateway to establish a connection to the service provider. Generally send instructions before you send a test to detect the current state of the MC35, the directive has the form "ATr"; in access gateway and flow control parameters passed AT instruction sets are finished, you can start by service code and service call 99 providers connect, instruction format as ATDT * 99 *** 1 # rn. If in the directive after a given period of time CONNECT information returned, it indicates that the service provider; otherwise the connection is made successfully, indicating dial fails, wireless transmission function fails to start. MC35 successfully log Monternet gateway will automatically switch from command mode to data communication model, and serial communication mode from the original query type become disruptive. At this point the system actively send a frame PPP request information, the service provider receives the request for information is proactively ask frames, consultations related parameter settings. Question service parameters and user authentication succeeds, the service provider to assign a separate IP system, and thus can be considered successful GPRS on-line.

Figure 4 GPRS wireless data transfer process

After successful GPRS on-line can be considered two main Department MC35 operating state: data transmission status and idle.

In data transmission status, MC35 of peak current of up to 400 mA; in the idle state is generally 15 mA. In addition, in an idle state MC35 also supports a variety of sleep mode. Considering that the system power consumption issues, enabled the Hibernate feature MC35. The system adopts the MC35 sleep mode. In the sleep mode, the current General 3 mA or so; MC35 from serial port or from the service provider receives the data, it will immediately be MC35 is set to normal mode, data transmission ends automatically after entering sleep mode. The sleep mode setting can be done by Directive "AT + CFUN = 7rn" to complete, and that the directive must be performed after the GPRS on-line. This can be in idle state automatically MC35 set to sleep mode, the current value from 15 to 3 mA mA. In the sleep instruction execution before the switch State involved MC35, since in the implementation of the directive before the MC35 in data communication mode, through Directive "+++" to switch to command mode, and then execute the sleep instruction. After the sleep instruction execution also through Directive "MC35 ATOr" will switch to the data communication mode; otherwise, the MC35 will put the data to be sent as instructions. 2.4 graphical user interface in the original location system uses Shenzhen Pont far company production of low-power, 128 × 64 dot matrix LCD module MOBI2006 to graphical display system information. MOBI2006 supports both parallel and serial data communication, the working voltage 3.3 V. In this system, use the S3C2410 i/o port analog LCD control sequence to achieve the control of the LCD. In the specific implementation of the relevant information is displayed when you use a Framebuffer technology. First of all a pre-allocated buffer and declared as a two-dimensional array, the arrayThe length of a one-dimensional and two-dimensional length respectively and LCD's width and height, so that each element of the array represents a point in a liquid crystal. In the system operation to flush liquid crystal display, you must first update the Framebuffer buffer, then from the Framebuffer updates LCD display. MOBI2006 columns based on a points addressed; horizontal page addressing based, each page consists of eight dots. Characteristics of liquid crystal-based, if not using Framebuffer technology, refresh the screen in a small block will cause changes in the entire screen, to the development of the upper application has caused great difficulties. Therefore, although using Framebuffer technology will occupy part of the memory and the refresh time, but to the subsequent development of a convenient: in the upper specific application is no longer subject to the limit, the page address in the upper-level developers seem to, horizontal column are the points addressed, can facilitate flexibility to manipulate the Panel. In addition, in order to ensure the synchronization of the Framebuffer and LCD, using event-based method to refresh the LCD and a partial refresh, saving both time and LCD refresh reduces screen jitter. For example, the application layer to display a picture, the picture is displayed, which corresponds to a two-dimensional array of values, the image's width and height, and the corresponding bitmap data. First pictures of raster data is flushed to the Framebuffer buffer, and then under the display location determine LCD refresh ranges, which buffer column that corresponds to the column value, but the LCD row values to be converted to liquid crystal page value can be converted using the following formula: Page_end = (row + high-1)/8: Page_start and Page_end which correspond to the liquid crystals start, terminate page value; row corresponds to the picture shows the location of horizontal; high corresponds to the height of an image. Calculate the corresponding page value after they adopted the following procedure refreshes the specified region of the LCD, complete picture of the show is expected.

for(page=p_s;page<=p_e;page++) { fc=column;for(lc=l_c_b;lc>l_c_e;lc--) //2{ GUI_Lcd_SetALL((u8_t)page,(u8_t)lc);for(f_bit=7;f_bit>=0;f_bit--) { if(!(

Frame_Buffer[page*LCD_PAGE+f_bit][fc]))GUI_Lcd_SendData(0); elseGUI_Lcd_SendData(1); }Delay(10); fc++; }} 2.5 data storage management position in the original S3C2410 BANK0 extends 1 slice in 4M× 16-bit NOR FLASH; in BANK6 extends in a 8M× 16-bit SDRAM, and NAND FLASH by using the S3C2410 controller extends a 64M× 8-bit NAND FLASH. NOR FLASH is mainly used for storing program code; NAND FLASH is mainly used to store the collection of ECG data as well as part of the program code. S3C2410 support from NOR and NAND two ways to start, you can configure the S3C2410 of OM [1: 0] to select the startup mode of the CPU. The system can achieve full day 24 hours ' continuous ECG data acquisition, which will produce large amounts of data. To a large number of ECG data transfer to PC for analysis, diagnosis, medical staff, the system uses a common USB port. S3C2410 internal integration of USB Device controller, therefore only have to design simple peripheral circuits, you can implement this functionality. The USB Device controller is fully compatible with USB1.1 protocol specification, integrates USB transfer device that supports the control transfer, interrupt transmission and bulk; 5 the endpoint with the FIFO, the bulk of endpoint provides DMA interface and support for suspend and remote wake-up function. 3 closing this system has the very strong usability, you can carry out real-time monitoring of heart patients. Because this system with radio transmission capabilities, so patients can withstand time and space restrictions on the use of this system, whether at home or in the field of the heart for real-time monitoring. System of 24-hour continuous ECG recording function to capture unexpected abnormal ECG data, health care professionals provide a strong basis of diagnosis. After the successful development of this system are the medical experts spoke highly of the clinical tests are also affected by patients and health professionals alike.