RoyalTek rgm-3000 用户手册

 

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but operates independently. The byte count 

refers to the payload byte length. Likewise, 

the check sum is a sum on the payload. 

The message length is transmitted high 

order byte first followed by the low byte. 

 

High Byte 

Low Byte 

<0x7F> Any 

value 

 

Even though the protocol has a maximum 

length of (215 -1) bytes practical 

considerations require the SiRF GPS 

module implementation to limit this value to 

a smaller number. Likewise, the SiRF 

receiving programs (e.g., SiRF demo) may 

limit the actual size to something less than 

this maximum.. 

The payload data follows the message 

length. It contains the number of bytes 

specified by the message length. The 

payload data may contain any 8-bit value. 

Where multi-byte values are in the payload 

data neither the alignment nor the byte order 

are defined as part of the transport although 

SiRF payloads will use the big-endian order. 

The check sum is transmitted high order 

byte first followed byte the low byte. This is 

the so-called big- endian order 

High Byte 

Low Byte 

<0x7F Any 

value 

The check sum is 15-bit checksum of the 

bytes in the payload data .The following 

pseudo code defines the algorithm used. Let 

message to be the array of bytes to be sent 

by the transport. Let msgLen be the number 

of bytes in the message array to be 

transmitted . 

Index = first 

checkSum = 0 

while index < msgLen 

checkSum = checkSum +message[index] 

checkSum = checkSum AND(2

15

-1) 

Note – All input messages are sent in BINARY 

format 

    SiRF Messages – Input Message List 

0 x 80 

128 

Initialize Data Source 

0 x 81 

129 

Switch to NMEA Protocol 

0 x 82 

130 

Set Almanac 

0 x 84 

132 

Software Version 

0x 85 

133 

DGPS Source Control 

0x 86 

134 

Set Main Serial Port 

0 x 88 

136 

Mode Control 

0 x 89 

137 

DOP Mask Control 

0 x 8A 

138 

DGPS Mode 

0 x 8B 

139 

Elevation Mask 

0 x 8C 

140 

Power Mask 

0 x 8D 

141 

Editing Residual 

0 x 8E 

142 

Steady-State Detection 

0 x 8F 

143 

Static Navigation 

0 x 90 

144 

Clock Status 

0 x 91 

145 

Set DGPS Serial Port