DSTARInterface User’s Guide
DSTARInterface is designed to run on any OS with any recent Java Virtual Machine. The interface requires the operating system and JVM to open the port in full duplex mode using a Java/serial-port interface. DSTARInterface is comprised of a number of classes which Java looks at as objects. The main class is DSTARInterface. This class is called at startup, sets parameters, and begins execution of the different support threads.
DSTARInterface works in conjunction with the javAPRSIGate TNCInterface to provide full, bidirectional communication with the serial port. All IGate logic is handled at in javAPRSIGate which leaves the DSTARInterface to concentrate on formatting and sending packets to the TNC log ports. DSTARInterface gates to and from the radio using standard TNC2 format strings. This allows remote APRS clients to operate as if they were connected to a TNC. All APRS packets have a CRC sequence added to the beginning of the line to reduce packet corruption. The same algorithm/technique used in computing the D-STAR RF header FCS is used for the TNC2 lines. The CRC string is stripped from line before gating to APRS-IS. The line is of the format $$CRCxxxx,AE5PL>APRS:rest of packet
DSTARInterface also converts the ICOM GPS-mode transmissions into an APRS posit. The first four letters of the GPS “message” are interpreted as a symbol per Appendix 2 of the APRS specification. A checksum (xor’ed from zero) prefixed by an asterisk is required in the GPS message. To simplify setting the GPS message, use the D-PRS Calculator at http://www.aprs-is.net/dprscalc.htm You must have JavaScript enabled in your browser to use that page
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