Cayman Systems 2E-H-W Manual de usuario descargar pdf (Pagina 10)

NMEA Manual based on MediaTek chipset - Manual

2 NMEA commands

NMEA commands are used to change or query settings of the module.

Command Length:

The maximum length of each packet is restricted to 255 bytes.

Command Contents:

Preamble: One byte character. ‘$’

NMEA ID: This will identify for the NMEA parser that it will receive commands for MediaTek.

Four bytes character string. “PMTK”

Command Number: Three-byte character string.

An identifier, from “000” to “999”, is used to tell the decoder how to decode the command.

DataField:

The DataField has a variable length depending on the command type.

A comma symbol ‘,’ must be inserted before each data field to help the decoder process the DataField.

*: 1 byte character.

The star symbol is used to mark the end of DataField.

CHK1, CHK2: Two-byte character string.

CHK1 and CHK2 are the checksum of the data between Preamble and ‘*’.

CR, LF: Two bytes binary data.

The two bytes are used to identify the end of a command.

Sample Command:

$PMTK000*32<CR><LF>

You can use your preferred terminal emulator to enter commands. For example, you can use TeraTerm,

whichcan be downloaded from here:

http://en.sourceforge.jp/projects/ttssh2/releases/

Remember to set the CR+LF for sending the command from the terminal program.

Figure 1: Tera Term terminal setup

Other possible terminal emulators to use include Putty and HyperTerminal.

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Cayman Systems 2E-H-W Manual de usuario Pagina 10