Biomedical Engineering Reference
In-Depth Information
9,600 kbps. A sensor node communicates with the BPM on this serial link to start
the reading process and receive the patient's blood pressure readings. Once the
readings are received, the sensor node communicates with the network and trans-
mits them to the base station.
The communication process in Fig.
2
initializes the sensor node by sending
start signal to the BPM to switch it to communication mode. Once the BPM is in
communication mode, the sensor node sends a command to open the communi-
cation port, then BPM is ready to receive commands. A command to take a
measurement is then issued. This causes the BPM to inflate the arm cuff and
acquire the blood pressure measurements. When reading process completes, the
readings are sent to the sensor node. Limited processing is performed by the sensor
node on the reading data before transmitting it through the network to the base
station. All communication with the BPM is in ASCII format.
Sensor Base Station to Host Computer Interface
Java is used to implement the interface between the base station and the host
computer. All communication between the base station and the PC is done through
the UART. A separate thread from the main GUI thread is used to maintain
constant monitoring of the serial port. When a message is received, the message
type is determined. If the message is a data message sent from a sensor node (i.e., a
measurement from one of the medical monitors), the data are extracted and stored
according to the ID of the sensor node that took the reading. If the message is a
control message, then the information is passed directly to the program thread
running the GUI. Control messages contain network information used to generate a
network view for the user. A control message from a sensor node includes the ID
of the sensor node and the ID of the router node used as the initial entry point into
the network. A control message generated by a router node contains the ID of the
originating router node itself and the ID of the router's partner node. The infor-
mation contained in the control message is used to generate a map of the network.
In the current implementation, the map is a simple tree depicting the network
structure.
The GUI
The GUI can be a Java-based program running on the host computer. All readings
received by the PC from the patient's sensor node will be stored in an object
corresponding to the patient. All stored readings can be viewed by selecting the
desired patient name in the list and selecting the ''View'' option. It allows the user
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