Siemens XT55 3.1.1 Extended NMEA Commands for XT55 only

XT55 AVL Software Instructions User’s Guide

Confidential/Preliminary s

mo b i l e

XT55_avl_ug_V01 Page 14 of 20 15.03.2004

3.1.1 Extended NMEA Commands – for XT55 only

The XT55 module accepts NMEA commands in the following formats:

$PSRF<command>,<parameter>, .. ,<parameter><* Checksum><CR> <LF>.

Command1 Parameter2 Checksum3 End Sequence

$PSRF11 Data *CKSUM <CR> <LF>

1 NMEA command

2 valid parameters

3 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))

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

Command Parameter Checksum End Sequence

$PSRF112, 21 *0A <CR> <LF>