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Document Title: 20
User’s Manual for the GPS Orion-S/-HD Receiver
Document No. Issue 1.0
GTN-MAN-0110 June 22, 2003
DLR/GSOCNo part of this document shall be reproduced in any form or disclosed to third parties without prior authorization.
4.2 Protocol Description
The Orion-S and –HD receivers employ the Mitel proprietary WinMon format for commands
and output messages. In addition, selected NMEA type output messages are supported.
Other than in the standard GPS Orion firmware (cf. [2]), the choice of WinMon and/or NMEA
messages is not controlled by the discrete input pin (slide switch) but configured by com-
mand. If desired, both message types may simultaneously be activated in the output stream.
4.2.1 WinMon Format
A WinMon sentence is basically an ASCII text string composed of a command or message
identifier, the data portion and a hexadecimal checksum (Fig. 4.1). The sentence is embed-
ded in a protocol frame made up of an initial Start of Transmission (STX) character (ASCII
0x02) and a terminating End of Transmission (ETX) character (ASCII 0x03).
STX C C x x x x … x x H H ETX
STX ‘F’ n n x x x … x x H H ETX
C = Alphabetic character (uppercase).
n = Decimal digit (0,…,9)
x = Data field.
H = Hexadecimal checksum character (uppercase).
STX = Start of Transmission (0x02).
ETX = End of Transmission (0x03).
Fig 4.1 WinMon sentence format and protocol frame for command (top) and output messages (bottom)
Command identifiers consist of two uppercase alphabetic characters, while a message iden-
tifier is made up of an initial ‘F’ character and a two digit decimal number
2
. The sentence
checksum is the hexadecimal representation of the exclusive-or of all the characters in the
sentence, excluding the <STX> and <ETX>. All data bytes contained in the data field of the
message are printable 7 bit characters (ASCII 32-127).
In extension of the original GPS Orion software, numerous new commands and output sen-
tences have been defined for the Orion-S and –HD receiver. Other than in the default sen-
tences, however, data fields of output messages are right justified for improved readability.
The format fields shown in the subsequent command and message descriptions illustrate the
fixed number of characters reserved for each data item, with “.” denoting the position of the
decimal point. Leading digits may be blank and an “s” indicates that the first non-blank char-
acter contains the sign of the respective quantity.
2
In extension of this rule, the F13, F14, F15, and F51 formats are jointly used for retrieving and loading specific
receiver data (almanac, ephemeris, ionosphere and trajectory parameters). However, these sentences must al-
ways follow a specific command (e.g. LA Load Almanacs) to initiate the upload and none of them will be proc-
essed on its own.