Digilent PmodGPS Referenzhandbuch - Seite 3

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PmodGPS™ Reference Manual
The PmodGPS uses sentences based on National Marine Electronics Association (NMEA) protocols for data output.
Each NMEA message begins with a ($) dollar sign. The next five characters are the talker ID and the arrival alarm.
The PmodGPS talker ID is "GP" and the arrival alarm is the specific sentence output descriptor. Individual comma
separated data fields follow these five characters. After the data fields there is an asterisk followed by a checksum.
Each sentence should end with <CR><LF>. For example output sentences refer to tables two through six at the end
of this manual.
User may configure some of the PmodGPS characteristics by writing command packets to the module. However,
these functions are more advanced and not all of the command packets are openly distributed. Users may change
the baud rate to 38.4kBd (minimum baud for 10Hz data acquisition) by issuing the following command over the
UART:
"$PMTK251,38400*27<CR><LF>"
The "*27" corresponds to a checksum, if users want to substitute a different baud rate, then they must calculate a
new checksum using GlobalTop's Checksum Tool. The command for changing the data acquisition from 1Hz to 10Hz
is:
"$PMTK226,3,30*4<CR><LF>"
The same checksum process for changing the baud rate applies to this change too. Contact GlobalTop for more
information on the individual command packets, their complete command list, or see their FAQ for how to change
the baud rate.
Any external power applied to the PmodGPS must be within 2.7V and 5.25V; however, it is recommended that
Pmod is operated at 3.3V.
Note: Refer to the GlobalTop FGPMMOPA6H datasheet at
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
Connector J1
Pin
Signal
Description
1
3DF
3D-Fix Indicator
2
RX
Receive
3
TX
Transmit
4
1PPS
1 Pulse Per Second
5
GND
Power Supply Ground
6
VCC
Power Supply (3.3v)
Connector J2
Pin
Signal
Description
1
~RST
Reset (active low)
DGPS data pin (contact
2
RTCM
GlobalTop for use)
Table 1. Interface connector signal descriptions.
here
for more information on the GPS module interface.
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