Siemens XT55 사용자 설명서

XT55 AVL Software Instructions User’s Guide 
Confidential/Preliminary 

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XT55_avl_ug_V01 

Page 14 of 20 

15.03.2004 

The XT55 module accepts NMEA commands in the following formats: 
 
$PSRF<command>,<parameter>, .. ,<parameter><* Checksum><CR> <LF>. 
 
 

$PSRF11 

Data 

*CKSUM 

<CR> <LF> 

 

 

NMEA command 

 valid parameters 

 the checksum consists of a “*” followed by two hex values. In order to calculate the Checksum, use 

your own application, which calculates the Checksum. Below a small source code is written in Visual 
Basic: 

 

Public Sub CheckSum(field As String) 

  If field = “” then 

   CS = “*” 

    CS = 0 

     For i = 1 to Len(field) 

      CS = CS Xor Asc(Mid$(field, i, 1)) 

      Next 

     CS = Hex(CS) 

    If Len(CS) =1 then  

   CS = “0” & CS 

  CS = “*” & CS 

 END SUB 

 
Therefore, the string over which the checksum has to be calculated is (see example below): 
field = PSRF112,21 //without the character “$”  
 
Example: 
$PSRF112,21*0A 
 

$PSRF112, 

21 

*0A 

<CR> <LF>