GPS Receiver Module
Li-ION BATTERY CHARGER OPERATION
GPS-41BTM
While the UT-41BTM is connected to the Li-ION rechargeable battery only, without the external 5V DC power
source, the red battery-low LED indicator will turn ON when output voltage of the Li-ION falls below 3.45V.
When the 5V DC source is connected to charge the Li-ION battery, the green charging-battery LED indicator
will turn ON. The battery will be charging at 48mA during the pre-charge phase until 2.93V is reached. Next,
charge current changes to 480mA during the full-charge phase until 4.1V is reached. Afterwards, charge
current will decrease gradually until 48mA is reached, and the charge current will fall to a very low value and
remain in the trickle charge phase. The green charging-battery LED indicator remains ON until the 5V DC
source is disconnected.
MEA Messages
The serial interface protocol is based on the National Marine Electronics Association’s NMEA 0183 ASCII
interface specification. This standard is fully define in “NMEA 0183, Version 3.01” The standard may be
obtained from NMEA, www.nmea.org
GGA - GPS FIX DATA
Time, position and position-fix related data (number of satellites in use, HDOP, etc.).
Format:
$GPGGA,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,M,<10>,M,<11>,<12>,*<13><CR><LF>
Example:
$GPGGA,104549.04,2447.2038,N,12100.4990,E,1,06,01.7,00078.8,M,0016.3,M,,*5C<CR><LF>
Field
1
2
3
4
5
6
7
8
9
10
11
12
13
Example
Description
104549.04 UTC time in hhmmss.ss format, 000000.00 ~ 235959.99
2447.2038 Latitude in ddmm.mmmm format
Leading zeros transmitted
N
Latitude hemisphere indicator, ‘N’ = North, ‘S’ = South
12100.4990 Longitude in dddmm.mmmm format
Leading zeros transmitted
E
Longitude hemisphere indicator, 'E' = East, 'W' = West
1
Position fix quality indicator
0: position fix unavailable
1: valid position fix, SPS mode
2: valid position fix, differential GPS mode
06
Number of satellites in use, 00 ~ 12
01.7
Horizontal dilution of precision, 00.0 ~ 99.9
00078.8 Antenna height above/below mean sea level, -9999.9 ~ 17999.9
0016.3
Geoidal height, -999.9 ~ 9999.9
Age of DGPS data since last valid RTCM transmission in xxx format (seconds)
NULL when DGPS not used
Differential reference station ID, 0000 ~ 1023
NULL when DGPS not used
5C
Checksum
Note:
The checksum field starts with a ‘*’ and consists of 2 characters representing a hex number. The
checksum is the exclusive OR of all characters between ‘$’ and ‘*’.
DS-41BTM-1 Feb ’06
©2006 RF Solutions Ltd, www.rfsolutions.co.uk
Tel 01273 898000 Fax 01273 480661
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