com.sun.spot.io.j2me.radio
Class RadioInputStream

java.lang.Object
  java.io.InputStream
      com.sun.spot.io.j2me.radio.RadioInputStream

public class RadioInputStream
extends InputStream

Helper class for "radio:" connections. This class provides an InputStream over the data received from another Spot. It also provides a small set of accessors to get information about the quality of the link. You should NOT normally instantiate this class directly, but rather via the GCF framework: see the first reference below for more details.

See Also:

RadioConnection

Constructor Summary

RadioInputStream(IPortBasedProtocolManager dispatcher, ConnectionID cid, long timeout)
Construct a RadioInputStream

Method Summary

int	available() Return the number of bytes available to be read from the stream without blocking.
void	close() Closes this input stream and releases any system resources associated with the stream.
int	getCorr() CORR measures the average correlation value of the first 4 bytes of the packet header.
int	getLinkQuality() Link Quality Indication (LQI) is a characterization of the quality of a received packet.
int	getRssi() RSSI (received signal strength indicator) measures the strength (power) of the signal for the packet.
int	read() Reads the next byte of data from the input stream.

Methods inherited from class java.io.InputStream

mark, markSupported, read, read, reset, skip

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RadioInputStream

public RadioInputStream(IPortBasedProtocolManager dispatcher,
                        ConnectionID cid,
                        long timeout)

Construct a RadioInputStream

Parameters:

dispatcher - the PortBasedProtocolManager that will dispatch radio packets

cid - the ConnectionID object being used

timeout - the timeout to use when waiting for input

Method Detail

read

public int read()
         throws IOException

Description copied from class: InputStream

Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

A subclass must provide an implementation of this method.

Specified by:

read in class InputStream

Returns:

the next byte of data, or -1 if the end of the stream is reached.

Throws:

IOException - if an I/O error occurs.

available

public int available()
              throws IOException

Return the number of bytes available to be read from the stream without blocking. Returns the number of bytes available in the current underlying radio packet - more packets might be coming but we just don't know.

Overrides:

available in class InputStream

Returns:

the number of bytes available right now

Throws:

IOException - if an I/O error occurs.

getLinkQuality

public int getLinkQuality()

Link Quality Indication (LQI) is a characterization of the quality of a received packet. Its value is computed from the CORR, correlation value. The LQI ranges from 0 (bad) to 255 (good).

Returns:

linkQuality - range 0 to 0xFF

See Also:

RadioPacket.getLinkQuality()

getCorr

public int getCorr()

CORR measures the average correlation value of the first 4 bytes of the packet header. A correlation value of ~110 indicates a maximum quality packet while a value of ~50 is typically the lowest quality packet detectable by the SPOT's receiver.

Returns:

- correlation value

See Also:

RadioPacket.getCorr()

getRssi

public int getRssi()

RSSI (received signal strength indicator) measures the strength (power) of the signal for the packet. It ranges from +60 (strong) to -60 (weak). To convert it to decibels relative to 1 mW (= 0 dBm) subtract 45 from it, e.g. for an RSSI of -20 the RF input power is approximately -65 dBm.

Returns:

- RSSI value

See Also:

RadioPacket.getRssi()

close

public void close()
           throws IOException

Description copied from class: InputStream

Closes this input stream and releases any system resources associated with the stream.

The close method of InputStream does nothing.

Overrides:

close in class InputStream

Throws:

IOException - if an I/O error occurs.