An ECG Monitoring System Based On MSP430

The ECG has been wildly used in diagnosing heart disease . At present , the ECG monitoring system have disadvantages . For example , it can not emit the signal real time and is not convenience . With the development of electron technology , wireless communication technology and computer technology , the ECG monitoring system is going to be smaller and more convenient.The ECG monitoring system which is designed in this paper based on the MSP430 Single Chip Micyoco . Using the wireless communication chip , nRF2401 , the emitting part send signals to the incepting part which translating the signals to the PC . The PC will analyzing and deal with the information.The main part of this system is new type,low power MCU MSP430 manufactured by TI company. This MCU is very suitable for ultra-low consumption situation, and it can work long time powered by battery. This MSP430F413 has low price, a good many function can achieved via software, use less hardware. So the cost of this system is cheap and it is in favor of extend application.MSP430 can debug online through JTAG., we only need a PC and a simulator during exploitation. We can use IAR Embedded Workbench for MSP430 and C-SPY as exploitation software. This feature can save time and money in exploitation.This system catch the ECG in the body ; the analogue ECG is transformed into digital ECG by amplifying circuit , filtering circuit and A/D converting circuit . The emitting and incepting part base on the chip nRF2401 . The function of the communicating with PC is to transmit the temperature to PC.This part use Timer_A to realize soft UART . In the way , the signal can be transmit safely . The cost of this system is low what with there is no hard UART .This system is made of three parts . The fist one can catch the ECG and translate it . We can get the normative I , II , III electrocardiogram by embedding electrode in the body .There is a selector to select the real-time signal which is going to send to amplifying circuit . The selector which is used in the paper is CD4052 . The ECG which is caught in the body is feebleness . We need to amply the signal . The amplifying circuit which is used in the paper is differential amplifying circuit . Analog filter is used to reduce the disturbing influence . The ECG is translated to digital signals by A/D circuit .TCL549 can accomplish the work in 17μs.The second part is the wireless communication . The main function of this part is transmitting ECG at long bowls . To carry out the function the nRF2401 is designed . The nRF2401 is wireless emitting and incepting chip . It worked in 2.4～2.5GHz ISM . There are a Frequency Synthesis a , a power amplifier , a oscillators and a modulator . The Ramp-rat and the communications channel can be enactment by software . It is energy-saving .When it is sending signal in -5bBm , the working current is only 10.5mA . When it is incepting signal , the working current is 18mA . It has several working mode which are low-power and is energy-saving and convenient . The nRF2401 can incept two channel with one antenna basing on a new technology ' DuoCeiverTM ' .The third part of the system is UART. The function of the part is to transmit the temperature to PC. This part use Timer_A to realize soft UART. The communication protocol is 1stop+8data+1start. The Baud-rate is 1200bit/s. This Baud-rate generates by Timer_A interrupt. We work out the time between each bit and make Timer_A to interrupt by the time. Data can be transmitted by interrupt program. RS232 protocol which applied by PC serial port is different from TTL which applied by MCU. We use SP3220E to transform TTL to RS232. SP3220E can operate from a 3.0V to 5.5V power supply, and it only needs 5 additional capacitances.UART program on PC is compiled by Visual Basic. We use MSComm to realize the function.This system can catch ECG accurately and can monitor ECG real time . It can memorize the movement of the patient by compiling software.