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Gilat Generic Antenna Interface Version 3
Reference Guide
July 2010
Revision 0.2
Document Number: DC-001940(B)
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Notice
This document contains information proprietary to Gilat Satellite Networks Ltd. and may not be reproduced in whole or in
part without the express written consent of Gilat Satellite Networks Ltd. The disclosure by Gilat Satellite Networks Ltd. of
information contained herein does not constitute any license or authorization to use or disclose the information, ideas or
concepts presented. The contents of this document are subject to change without prior notice.
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Contents
Chapter 1: Introduction ............................................................................................................. 3
Overview .................................................................................................................... 3
Generic Antenna Protocol Format ................................................................................ 3
Chapter 2: Interfacing Using the Generic Antenna Protocol (Versions 2 and 3) ...................... 5
Protocol Sequence ................................................................ ...................................... 5
Generic Antenna Commands ....................................................................................... 6
Generic Antenna Commands - Examples................................................................ 8
Modem (VSAT) Response Commands......................................................................... 8
Modem (VSAT) Response Commands - Examples ................................................. 9
Chapter 3: Interfacing Using the Generic Antenna Protocol (Version 3) ............................... 11
Protocol Sequence ................................................................ .................................... 11
Recovery from Modem Reset .................................................................................... 12
Recovery from Link Reset ......................................................................................... 12
Generic Antenna Commands ..................................................................................... 13
Generic Antenna Commands - Examples.............................................................. 15
Modem (VSAT) Response Commands....................................................................... 16
Modem (VSAT) Response Commands - Examples ............................................... 17
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Chapter 1: Introduction
In This Chapter
Overview .................................................................................................................... 3
Generic Antenna Protocol Format ................................................................................ 3
Overview
The stabilized or in-motion antenna provides a monitoring SOTM (SatelliteOn-the-Move) platform. Gilat SkyEdgeII modem (VSAT) provides highly
reliable network communication means. This document proposes that these
early mentioned systems generate two-channel interfacing loosely based on
the NMEA 0183 data protocol. The interfacing occurs via RS232 serial port at
9600-N-8-1 baud without any authentication or encryption in the link. To
enable interfacing, it is not required to log in to the SkyEdgeII system (none
security settings are implemented within it).
This document describes the command - response sequence between the
antenna and Gilat SkyEdgeII modem (VSAT).
Generic Antenna Protocol Format
All data in the Generic Antenna protocol are transmitted in the form of
messages. Only printable ASCII characters and CR (carriage return) and LF
(line feed) are allowed. Each message starts with a "$" sign and ends with
<CR><LF>.
The general format of a sentence is: $ttsss,d1,d2,....<CR><LF>.
The first two characters "tt", following the "$", are the talker identifiers. The
next three characters "sss" are the message identifiers. The "sss" characters
are followed by a number of data fields (separated by commas), mandatory
checksum, and terminated by carriage return and line feed. The data fields
are uniquely defined for each message type.
A message may contain up to 80 characters, the "$" and CR/LF signs. If data
for a field are not available, the field is omitted, but the delimiting commas
still appear, with no space between them.
The checksum field consists of a "*" sign and two hex digits representing the
exclusive OR (XOR) of all characters in-between, but not including the "$"
and "*" signs.
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Chapter 2: Interfacing Using the Generic Antenna
Protocol (Versions 2 and 3)
In This Section
Protocol Sequence ...................................................................................................... 5
Generic Antenna Commands ...................................................................................... 6
Modem (VSAT) Response Commands ......................................................................... 8
Protocol Sequence
This section illustrates the protocol (Versions 2 and 3) sequence between
antenna and Gilat SkyEdgeII modem (VSAT).
Refer to the following key that explains the commands in protocol sequence
(see Figure 1):
Talker ID
GA - Generic Antenna
SE - SkyEdge Modem
GP - GPS Unit
Message ID
SMT - Start Modem Tracking
TXM - Transmission Mute
GGA - Global Positioning System Fix Data
STS - Mode Status
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Generic Antenna Commands Interfacing Using the Generic Antenna Protocol (Versions 2 and 3)
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Figure 1: Protocol Sequence
Generic Antenna Commands
This section describes the messages issued by the antenna to Gilat
SkyEdgeII modem (VSAT). These messages appear in Generic Antenna
protocol of both versions (V.2 and V.3).
Table 1: Generic Antenna Protocol Commands
Command
Name
Message
Message Details
Description
Poll Modem
Lock Status
$GASMT,S,R*X
X<CR><LF>
$ - Open flag
GA - Generic Antenna
SMT - Start Modem
Tracking
S - (0) Stop; (1) Start
R - Rate: (0) one time;
(1..10) continuously, in
Hz
*XX - Check Sum
This message is
issued by the
antenna to Gilat
SkyEdgeII modem
(VSAT) to receive
lock status
response from the
modem.
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Generic Antenna Commands
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Command
Name
Message
Message Details
Description
Tx mute
$GATXM,E*XX<
CR><LF>
$GATXM,E*XX<CR><LF>
$ - Open flag
GA - Generic Antenna
TXM - Transmission
Mute
E - Enable transmission
:
(0) Disable modem
transmission
(1) Enable modem
transmission
*XX - Check Sum
This message is
issued to disable /
enable
transmission from
Gilat SkyEdgeII
modem (VSAT).
The message can
be issued more
than once per state
change.
Current
Position
$GPGGA,hhm
mss.ss,ddmm
.mmm,a,ddd
mm.mmm,b,q
,xx,p.p,a.b,
M,c.d,M,x.x,
nnnn
*XX<CR><LF>
hhmmss.ss - UTC of
position
ddmm.mmm - Latitude of
position
a - N or S, Latitude
hemisphere
dddmm.mmm -
Longitude of position
b - E or W, Longitude
hemisphere
q - GPS Quality indicator
(0) No fix;
(1) Non-differential GPS
fix;
(2) Differential GPS fix;
(6) Estimated fix;
xx - Number of satellites
in use
p.p - Horizontal dilution
of precision
a.b - Antenna altitude
above mean-sea-level
M - Units of antenna
altitude, meters
c.d - Geoidal height
M - Units of geoidal
height, meters
.x - Age of Differential
GPS data (seconds since
last valid RTCM
transmission)
The current
position is supplied
to Gilat SkyEdgeII
modem (VSAT) by
the following
NMEA0183 protocol
message.
The rate the
message should be
sent to the modem
is between once a
second to once a
minute.
It is recommended
to send the
message as often
as possible to
enable fast return
link recovery.
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Command
Name
Message
Message Details
Description
nnnn - Differential
reference station ID,
0000 to 1023
*XX - Check Sum
All fields marked in red
are obligatory for Gilat's
implementation
Generic Antenna Commands - Examples
This section illustrates the Generic Antenna commands' examples.
Table 2: Generic Antenna Commands - Examples
Command Name
Message Example
Poll Modem Lock Status
$GASMT,1,0*4D - start track, one shot
$GASMT,1,1*4C - start track, once a
second
$GASMT,1,10*7C - start track, 10 times
a second
$GASMT,0,0*4C - stop track
Tx mute
$GATXM,1*5A - enable Tx
$GATXM,0*5B - disable Tx
Current Position
$GPGGA,141454,3205.8163,N,03451.
3271,E,1,04,3.8,,M,19.2,M,,*64 - PGS
location
Modem (VSAT) Response Commands
This section describes the message issued by Gilat SkyEdgeII modem (VSAT)
to antenna.
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Modem (VSAT) Response Commands
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Table 3: Modem Response Commands
Command
Name
Message
Message Details
Description
Modem
Lock
Status
$SESTS,A,
BBBBBBB,S
S.SS*XX<C
R><LF>
$ - Open flag
SE - SkyEdge
STS - Status
A - Modem CD: (0) – not
locked on signal,
(1) – Locked on signal
BBBBBBB - Downlink center
frequency in Khz
SS.SS - Downlink SNR
[dB], valid only when A=1
*XX - Check Sum
This message is
transmitted from Gilat
SkyEdgeII modem
(VSAT) to antenna after
receiving the poll
modem command.
Modem (VSAT) Response Commands - Examples
This section illustrates the modem response commands' examples.
Table 4: Modem Response Commands - Examples
Command Name
Message Examples
Modem Lock Status
$SESTS,0,1121000,00.00*43 -
modem status V.2 - no lock
$SESTS,1,1121000,11.37*46 -
modem status V.2 - OB lock
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Chapter 3: Interfacing Using the Generic Antenna
Protocol (Version 3)
In This Section
Protocol Sequence .................................................................................................... 11
Recovery from Modem Reset .................................................................................... 12
Recovery from Link Reset.......................................................................................... 12
Generic Antenna Commands ..................................................................................... 13
Modem (VSAT) Response Commands ....................................................................... 16
Protocol Sequence
This section illustrates the protocol (Version 3) sequence between antenna
and Gilat SkyEdgeII modem (VSAT).
The Generic Antenna protocol (Version 3) enables higher communication baud
rate and more detailed modem status (information about the return link and
transmission status). It supports all legacy Generic Antenna protocol (Version 2)
commands. Only the format of the $SESTS modem command response differs
between the two early mentioned protocol versions.
Refer to the following key that explains the commands in protocol sequence
(see Figure 2):
Talker ID
GA - Generic Antenna
SE - SkyEdge Modem
Message ID
PCL - Set Protocol Version
GIN - Get Modem Information
OPT - Set Protocol Options
IGG - Work without GGA Message
SIN - Set Antenna Information
Ack - Modem Acknowledgment
INF - Modem Information
STS - Mode Status
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Recovery from Modem Reset Interfacing Using the Generic Antenna Protocol (Version 3)
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Figure 2: Protocol Sequence
Recovery from Modem Reset
When Gilat SkyEdgeII modem (VSAT) is reset or power-cycled, it returns to
its default configuration (protocol V.2, baud rate 9600, GPS).
In the following scenarios, the antenna should assume that the Gilat
SkyEdgeII modem (VSAT) has been reset. In these cases, it must renegotiate the configuration:
The modem does not issue Ack commands – the modem was returned to
protocol V.2.
Communication with modem has been lost for more than 60 seconds –
baud rate mismatch after reset.
Recovery from Link Reset
When the antenna recognizes that the return link is down (online status in
$SESTS, see below) or when the antenna issues Tx resume command, it is
recommended to send the $GPGGA command every second for fast link
recovery.
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Generic Antenna Commands
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After the link is recovered, the rate can be decreased up to once a minute.
Generic Antenna Commands
This section describes the messages issued by the antenna to Gilat
SkyEdgeII modem (VSAT). These messages appear in protocol V.3 only.
Table 5: Generic Antenna Commands
Command
Name
Message
Message Details
Description
Negotiate
Protocol
Version
$GAPCL,V
*XX<CR><
LF>
Reply:
$SEACK
$ - Open flag
GA - Generic
Antenna
PCL - Protocol's
Version
V - Version
(currently only 3)
*XX - Check Sum
This message is issued by
the antenna to Gilat
SkyEdgeII modem (VSAT) to
negotiate the protocol
version.
The antenna announces its
desired protocol's version.
The modem sends an Ack
message with the highest
supported protocol version.
In case the modem sends a
Nack message, the modem
falls back to protocol V.2.
Get Modem
Information
$GAGIN*X
X<CR><LF
>
Reply:
$SEINF
$ - Open flag
GA - Generic
Antenna
GIN - Get Modem
Information
*XX - Check Sum
This message is issued by
the antenna to Gilat
SkyEdgeII modem (VSAT) to
receive VSAT's type
information.
This information can be used
by the antenna to display the
modem type in case it has
user interface.
In case in the future different
types of Gilat modems
behave differently, this
information will enable the
antenna to handle different
types of modems.
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Generic Antenna Commands Interfacing Using the Generic Antenna Protocol (Version 3)
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Command
Name
Message
Message Details
Description
Negotiate
Protocol
Options
$GAOPT,B
*XX<CR><
LF>
Reply:
$SEACK
$ - Open flag
GA - Generic
Antenna
OPT - Protocol
Options
B - Baud Rate [9600,
14400, … 115200]
*XX - Check Sum
This message is issued by
the antenna to Gilat
SkyEdgeII modem (VSAT) to
negotiate the protocol
options (currently only the
baud rate can be modified).
The command is issued at
last negotiated baud rate.
The antenna announces its
desired baud rate. The
modem sends an Ack
message with the acceptable
baud rate.
In case the modem sends a
Nack message, it sets its
baud rate to default value of
9600 baud.
Enable
working
without GPS
$GAIGG*X
X<CR><LF
>
Reply:
$SEACK
$ - Open flag
GA - Generic
Antenna
IGG - Ignore GGA
message
*XX - Check Sum
This message is issued by
the antenna to Gilat
SkyEdgeII modem (VSAT) to
enable the modem working
without up-to-date position
information (in case there is
no GPS in the system).
In this mode, the modem
does not wait for GPGGA
command to establish the
return link.
The position information is
updated by the user using
the modem SkyManage web
interface.
This command replaces the
GPGGA command when
working in without GPS.
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Generic Antenna Commands
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Command
Name
Message
Message Details
Description
Set Antenna
Information
$GASIN,V
,M*XX<CR
><LF>
Reply:
$SEACK
$ - Open flag
GA - Generic
Antenna
SIN - Set Antenna’s
Information
V - Antenna's Vendor
name, null terminated
string, up to 64
characters
M - Antenna's Model
name, null terminated
string, up to 64
characters
V,M are strings, max
length of 64
characters.
The strings are not
NULL-terminated.
They are delimited
using the command’s
comma. It is the
receiver’s side
responsibility to add
the NULL terminator
internally.
*XX - Check Sum
This message is issued by
the antenna to Gilat
SkyEdgeII modem (VSAT) to
update the modem with the
Antenna’s information.
The received information is
used for display only.
Generic Antenna Commands - Examples
This section illustrates the Generic Antenna commands' examples.
Table 6: Generic Antenna Commands - Examples
Command Name
Message Example
Negotiate Protocol Version
$GAPCL,3*46 - set protocol version
to 3 -
$SEACK,GAPCL,1*37 - ack on set
protocol version -
Get Modem Information
$GAGIN*46 - get modem information
-
Negotiate Protocol Options
$GAOPT,1152000*56 - set baud
rate to 115200 -
$SEACK,GAOPT,1*23 - ack on set
baud rate
Enable Working without GPS
GPS - $GAIGG*4F - ignore GGA -
work without
$SEACK,GAIGG,0*20 - Nack on
ignore GGA
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Command Name
Message Example
Set Antenna Information
$GASIN,AMERICOM,TS23L3*38 -
set antenna information
$SEACK,GASIN,1*3C - ack antenna
information
Modem (VSAT) Response Commands
This section describes the messages issued by Gilat SkyEdgeII modem
(VSAT) in response to the modem commands.
Table 7: Modem Response Commands
Command
Name
Message
Message Details
Description
Modem Ack
$SEACK,C,S*X
X<CR><LF>
$ - Open flag
SE - SkyEdge
ACK - Command
Acknowledgment
C - Antenna
command, without the
dollar ($) sign.
S - Success
(0) Fail (nack);
(1) Success (ack)
*XX - Check Sum
This message is
transmitted from Gilat
SkyEdgeII modem
(VSAT) to acknowledge
an antenna’s
command.
The message includes
the acknowledged
command and success
flag.
Modem
Information
$SEINF,P,V,S
,T*XX<CR><LF
>
$ - Open flag
SE - SkyEdge
INF - Status
P - Protocol Version
(3)
V - Vendor (Gilat)
S - System
(SkyEdgeII)
T - Modem Type
(“IP”, “IP Extend”,
“Access”, “Pro”)
V,S,T are strings, max
length of 30
characters.
The strings are not
NULL-terminated. They
are delimited using the
command’s comma. It
is the receiver’s side
responsibility to add
the NULL terminator
internally.
*XX - Check Sum
This message is
transmitted from Gilat
SkyEdgeII modem
(VSAT) after receiving
the Get Modem
Information
command.
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Modem (VSAT) Response Commands
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Command
Name
Message
Message Details
Description
Modem Lock
Status
$SESTS,A,BBB
BBBB,SS.SS,C
CCCCCC,O,T*X
X <CR><LF>
$ - Open flag
SE - SkyEdge
STS - Status
A - Forward channel
Carrier Detect:
(0) – Not locked on
signal
(1) – Locked on signal
BBBBBBB - Downlink
center frequency [KHz]
SS.SS - Downlink SNR
[dB], valid only when
A=1
CCCCCCC - Return link
center frequency [KHz]
O - Online status
(0) – Offline (out of
network)
(1) – Online (login the
network)
T - Tx Enable
(0) – Tx Mute
(1) – Tx Enable
*XX - Check Sum
This message is
transmitted from Gilat
SkyEdgeII modem
(VSAT) after receiving
the poll modem status
command.
Note: This message
format was modified in
compare to protocol
V.2.
Modem (VSAT) Response Commands - Examples
This section illustrates modem response commands' examples.
Table 8: Modem Response Commands - Examples
Command Name
Message Examples
Modem Information
$SEINF,3,GILAT,SkyEdgeII,IP*48 -
get modem information - protocol V.3,
vendor GILAT, system SkyEdgeII,
modem IP
Modem Lock Status
$SESTS,1,1121000,08.24,1200000,
1, 0*4D - modem status V.3 - OB
lock, 1121000KHz, 8.24dB,
1200000KHz, online, Tx disable (mute)
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