PATIENT DATA TRANSMISSION BETWEEN PC AND MICROCOMPUTER ON RS-485 NETWORK

Abstract

In this dissertation work a network is developed for the patient data transfer, the network follows RS-485 standard for physical connections among the devices. The devices communicate with PC, which act as master using modbus protocol. Modbus Protocol defines the structure of message which is recognized by master and slave devices. The master sends the query to the slave and expects the response from the concerned slave device. When the slave receives a valid query, it composes a response accordingly and returns it to the master. The response of the slave contains its own address function code, subfunction code and the requested patient data,(which could be ECG data, blood pressure or heart ratejand CRC.The subfunction code decides the length or duration of the ECG data. The master receives data and performs CRC check if it fails, master discards all other data and takes the control of transmission line else if CRC check passes, ECG wave is plotted on the screen of the PC.