NMEA Manual based on MediaTek chipset - Manual
FTX-HW-13002-A
Preliminary
Page 9 of 39
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.
