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MX4200 Receiver Data Format

Table of Contents

Control Port Sentences

The Control (CDU) Port is used to initialize, monitor, and control the receiver. The structure of the control port sentences is based on the NMEA-0183 Standard for Interfacing Marine Electronics Navigation Devices (version 1.5). For more details, please refer to the NMEA-0183 Specification available from the National Marine Electronics Association.

Reserved characters are used to indicate the beginning and the end of records in the data stream, and to delimit data fields within a sentence. Only printable ASCII characters (Hex 20 through 7F) may be used in a sentence. Table 2 lists the reserved characters and defines their usage. Table 1 illustrates the general Magnavox proprietary NMEA sentence format.

Table 1. Magnavox Proprietary NMEA Sentence Format

$PMVXG,XXX,...................*CK

Character Meaning
$ Sentence Start Character
P Special ID (P = Proprietary)
MVX Originator ID (MVX = Magnavox)
G Interface ID (G = GPS)
XXX Sentence Type
... Data
* Optional Checksum Field Delimiter
CK Optional Checksum

Table 2. NMEA Sentence Reserved Characters

Character Hex Value Usage
$ 24 Start of Sentence Identifier
{cr}{lf} 0D 0A End of Sentence Identifier
, 2C Sentence Delimiter
* 2A Optional Checksum Field Delimiter

Following the start character $, are five characters which constitute the block label of the sentence. For Magnavox proprietary sentences, this label is always PMVXG. The next field after the block label is the sentence type, consisting of three decimal digits.

The data, delimited by commas, follows the sentence type. Note that the receiver uses a free-format parsing algorithm, so you need not send the exact number of characters shown in the examples. You will need to use the commas to determine how many bytes of data need to be retrieved.

The notation CK shown in Table 1 symbolically indicates the optional checksum in the examples. The checksum is computed by exclusive-ORing all of the bytes between the $ and the * characters. The $, * and the checksum are not included in the checksum computation.

Checksums are optional for Control Port input sentences, but are highly recommended to limit the effects of communication errors. Magnavox receivers always generate checksums for Control Port output sentences.

ASCII data characters are transmitted in the following format:

Data Bits 8 (msb always 0)
Parity None
Stop Bits 1

NULL fields are fields which do not contain any data. They would appear as two commas together in the sentence format, except for the final field. Some Magnavox proprietary sentences require that the format contain NULL fields. mandatory NULL fields are identified by an '*' next to the respective field.

Control Port Input Sentences

These are the subset of the MX4200 control port input sentences sent by the NTP driver to the GPS receiver.

$PMVXG,000

Initialization/Mode Control - Part A

Initializes the time, position and antenna height of the MX4200.

Field Description Units Format Default Range
1 Day   Int   1-31
2 Month   Int   1-12
3 Year   Int   1991-9999
4 GMT Time HHMMSS Int   000000-235959
5 WGS-84 Latitude DDMM.MMMM Float 0.0 0 - 8959.9999
6 North/South Indicator   Char N N,S
7 WGS-84 Longitude DDDMM.MMMM Float 0.0 0 - 17959.9999
8 East/West Indicator   Char E E,W
9 Altitude (height above Mean Sea Level) in meters (WGS-84) Meters Float 0.0 +/-99999.0
10 Not Used        
Example:
$PMVXG,000,,,,,,,,,,*48
$PMVXG,000,,,,,5128.4651,N,00020.0715,W,58.04,*4F

$PMVXG,001

Initialization/Mode Control - Part B

Specifies various navigation parameters: Altitude aiding, acceleration DOP limits, and satellite elevation limits.

Field Description Units Format Default Range
*1 Constrain Altitude   Int 1 0=3D Only
1=Auto
2=2D Only
2 Not Used        
*3 Horizontal Acceleration Factor m/sec^2 Float 1.0 0.5-10.0
*4 Not Used        
*5 VDOP Limit   Int 10 1-9999
*6 HDOP Limit   Int 10 1-9999
7 Elevation Limit Deg Int 5 0-90
8 Time Output Mode   Char U U=UTC
L=Local Time
9 Local Time Offset HHMM Int 0 +/- 0-2359
Example:
$PMVXG,001,3,,0.1,0.1,10,10,5,U,0*06

$PMVXG,007

Control Port Output Configuration

This message enables or disables output of the specified sentence and defines the output rate. The user sends this message for each sentence that the receiver is to output.

Field Description Units Format Default Range
1 Control Port Output Block Label   Char    
2 Clear Current Output List   Int   0=No
1=Yes
3 Add/Delete Sentence from List   Int   1=Append
2=Delete
4 Not Used        
5 Sentence Output Rate Sec Int   1-9999
6 # digits of Precision for CGA and GLL sentences   Int 2 2-4
7 Not Used        
8 Not Used        
Example:
$PMVXG,007,022,0,1,,1,,,*4F

$PMVXG,023

Time Recovery Configuration

This message is used to enable/disable the time recovery feature of the receiver. The time synchronization for the 1PPS output is specified in addition to a user time bias and an error tolerance for a valid pulse. This record is accepted in units configured for time recovery. If the back panel contains a 1PPS outlet, the receiver is a time recovery unit.

Field Description Units Format Default Range
*1 Time Recovery Mode   Char D D=Dynamic
S=Static
K=Known Position
N=No Time Recovery
2 Time Synchronization   Char G U=UTC
G=GPS
3 Time Mark Mode   Char A A=Always
V=Valid Pulses Only
4 Maximum Time Error Nsec Int 100 50-1000
5 User Time Bias Nsec Int 0 +/- 99999
6 ASCII Time Message Control   Int 0 0=No Output
1=830 to Control Port
2=830 to Equipment Port
7 Known Pos PRN   Int 0 1-32
0=Track All Sats
Example:
$PMVXG,023,S,U,A,500,0,1,*16

$CDGPQ,YYY

Query From a Remote Device / Request to Output a Sentence

Enables the controller to request a one-time transmission of a specific block label. To output messages at a periodic rate, refer to input sentence $PMVXG,007.

Field Description Units Format Default Range
1:CD ID of Remote Device   Char   (See NMEA-0183)
2:GP GPS   Char   (See NMEA-0183)
3:Q Query   Char   (See NMEA-0183)
4:YYY Label of Desired Sentence   Char   Any Valid NMEA or Magnavox Sentence Type
Example:
$CDGPQ,030*5E

Control Port Output Sentences

These are the subset of the MX4200 control port output sentences recognized by the NTP driver.

$PMVXG,000

Receiver Status

Returns the current status of the receiver including the operating mode, number of satellites visible, and the number of satellites being tracked.

Field Description Units Format Range
1 Current Receiver Status   Char ACQ=Reacquisition
ALT=Constellation Selection
IAC=Initial Acquisition
IDL=Idle, No Satellites
NAV=Navigating
STS=Search The Sky
TRK=Tracking
2 Number of Satellites that should be Visible   Int 0-12
3 Number of Satellites being Tracked   Int 0-12
4 Time since Last Navigation HHMM Int 0-2359
5 Initialization Status   Int 0=Waiting for Initialization
1=Initialization Complete
Example:
$PMVXG,000,TRK,3,3,0122,1*19

$PMVXG,021

Position, Height, Velocity

This sentence gives the receiver position, height, navigation mode and velocity north/east. This sentence is intended for post analysis applications.

Field Description Units Format Range
1 UTC Measurement Time Seconds into the week Float 0-604800.00
2 WGS-84 Latitude DDMM.MMMM Float 0-89.9999
3 North/South Indicator   Char N, S
4 WGS-84 Longitude DDDMM.MMMM Float 0-179.9999
5 East/West Indicator   Char E, W
6 Altitude (MSL) Meters Float  
7 Geoidal Height Meters Float  
8 Velocity East M/Sec Float  
9 Velocity North M/Sec Float  
10 Navigation Mode   Int Navigating
1=Position From a Remote Device
2=2D
3=3D
4=2D differential
5=3D differential
Not Navigating
51=Too Few Satellites
52=DOPs too large
53=Position STD too large
54=Velocity STD too large
55=Too many iterations for velocity
56=Too many iterations for position
57=3 Sat Startup failed
Example:
$PMVXG,021,142244.00,5128.4744,N,00020.0593,W,00054.4,0047.4,0000.1,-000.2,03*66

$PMVXG,022

DOPs

This sentence reports the DOP (Dilution Of Precision) values actually used in the measurement processing corresponding to the satellites listed. The satellites are listed in receiver channel order. Fields 11-16 are output only on 12-channel receivers.

Field Description Units Format Range
1 UTC Measurement Time Seconds into the week Float 0-604800.00
2 East DOP (EDOP)   Float  
3 North DOP (NDOP)   Float  
4 Vertical DOP (VDOP)   Float  
5 PRN on Channel #1   Int 1-32
6 PRN on Channel #2   Int 1-32
7 PRN on Channel #3   Int 1-32
8 PRN on Channel #4   Int 1-32
9 PRN on Channel #5   Int 1-32
10 PRN on Channel #6   Int 1-32
11 PRN on Channel #7   Int 1-32
12 PRN on Channel #8   Int 1-32
13 PRN on Channel #9   Int 1-32
14 PRN on Channel #10   Int 1-32
15 PRN on Channel #11   Int 1-32
16 PRN on Channel #12   Int 1-32
Example:
$PMVXG,022,142243.00,00.7,00.8,01.9,27,26,10,09,13,23*77

$PMVXG,030

Software Configuration

This sentence contains the navigation processor and baseband firmware version numbers.

Field Description Units Format Range
1 Nav Processor Version Number   Char  
2 Baseband Firmware Version Number   Char  
Example:
$PMVXG,030,DA35,015

$PMVXG,101

Control Sentence Accept/Reject

This sentence is returned (on the Control Port) for every $PMVXG and $XXGPQ sentence that is received.

Field Description Units Format Range
1 Sentence ID   Char  
2 Accept/Reject Status   Int 0=Sentence Accepted
1=Bad Checksum
2=Illegal Value
3=Unrecognized ID
4=Wrong # of fields
5=Required Data Field Missing
6=Requested Sentence Unavailable
3 Bad Field Index   Int  
4 Requested Sentence ID (If field #1 = GPQ)   Char  
Example:
$PMVXG,101,GPQ,0,,030*0D

$PMVXG,523

Time Recovery Configuration

This sentence contains the configuration of the time recovery function of the receiver.

Field Description Units Format Range
1 Time Recovery Mode   Char D=Dynamic
S=Static
K=Known Position
N=No Time Recovery
2 Time Synchronization   Char U=UTC Time
G=GPS Time
3 Time Mark Mode   Char A=Always Output Time Pulse
V=Only when Valid
4 Maximum Time Error for which a time mark will be considered valid Nsec Int  
5 User Time Bias Nsec Int  
6 Time Message Control   Int 0=No Message
1=830 to Control Port
2=830 to Equipment Port
7 Not Used      
Example:
$PMVXG,523,S,U,A,0500,000000,1,0*23

$PMVXG,830

Time Recovery Results

This sentence is output approximately 1 second preceding the 1PPS output. It indicates the exact time of the next pulse, whether or not the time mark will be valid (based on operator-specified error tolerance), the time to which the pulse is synchronized, the receiver operating mode, and the time error of the last 1PPS output. The leap second flag (Field #11) is not output by older receivers.

Field Description Units Format Range
1 Time Mark Valid   Char T=Valid
F=Not Valid
2 Year   Int 1993-
3 Month   Int 1-12
4 Day Nsec Int 1-31
5 Time HH:MM:SS Int 00:00:00-23:59:59
6 Time Synchronization   Char U=UTC
G=GPS
7 Operating Mode   Char D=Dynamic
S=Static
K=Known Position
8 Oscillator Offset - estimate of oscillator frequency error PPB Int  
9 Time Mark Error of last pulse Nsec Int  
10 User Time Bias Nsec Int  
11 Leap Second Flag - indicates that a leap second will occur. This value is usually zero except during the week prior to a leap second occurrence, when this value will be set to +/-1. A value of +1 indicates that GPS time will be 1 second further ahead of UTC time.   Int -1,0,1
Example:
$PMVXG,830,T,1998,10,12,15:30:46,U,S,000298,00003,000000,01*02