LS20031 GPS

LS20031 GPS Small, lightweight, easy to use and accurate. Device Information Manufacturer LOCOSYS Chipset MediaTek MT3329 Interface TTL Serial Baud Rate 4800 to 115200 Update Rate 1 to 10Hz Voltage 3.3v Channels 66 DGPS Capable of SBAS (WAAS, EGNOS, MSAS) LED Indicator Yes, blinks once per second when locked Dimensions 30 x 30 x 7.2 mm

The LS20031 is an amazing little GPS unit. It’s small, lightweight, easy to use and accurate. It even has a built-in micro battery to preserve system data for rapid satellite re-acquisition.

Suppliers

• SparkFun, also in retail packaging.
• Pololu

Datasheet and Schematic

• Datasheet: Media:LS20030-3_datasheet_v1.2.pdf (mostly useless and wrong)
• Schematic: None

Don’t let the datasheet fool you, the GPS defaulted to a baud rate of 57600 8N1 and not the 9600 8N1 that the datasheet claims.

Pinout

1. Vcc
2. RX
3. TX
4. GND
5. GND or not connected

Sparkfun has an excellent tutorial on preparing the LS20031 for use on a breadboard.

Commands

This board accepts standard MTK/NMEA commands and outputs in the same format. When sending commands to the GPS you must ensure that the checksum is correct, otherwise the command will be ignored. I recommend using the handy MTK NMEA checksum calculator. Commands must also be terminated by a CRLF (“\r\n”).

Baud Rate

Baud rate is set with the $PMTK251 command. For example, to set the baud rate to 9600:

$PMTK251,9600*17\r\n

Update Rate

SparkFun recommends sticking to 5Hz, as it is more reliable than 10Hz on this device. 1Hz Output:

$PMTK220,1000*1F\r\n

2Hz Output:

$PMTK220,500*2B\r\n

4Hz Output:

$PMTK220,250*29\r\n

5Hz Output:

$PMTK220,200*2C\r\n

10Hz Output:

$PMTK220,100*2F\r\n

GPS Augmentation Settings

Enable SBAS:

$PMTK313,1*2E\r\n

Disable SBAS:

$PMTK313,0*2F\r\n

Query SBAS:

$PMTK413*34\r\n

• 0 = Disabled
• 1 = Enabled

Enable WAAS:

$PMTK301,2*2E\r\n

Disable WAAS:

$PMTK301,0*2C\r\n

Query WAAS/DGPS:

$PMTK401*37\r\n

• 0 = Disabled
• 1 = RTCM
• 2 = WAAS

Usage

Linux

I recommend using Minicom to view the raw output. If you need to configure the GPS you can use the echo command, once you are listening to the incoming data at the right baud in minicom. Here’s an example command for setting the baud rate to 9600:

echo -e '$PMTK251,9600*17\r' > /dev/ttyUSB0

Windows

Mac

Embedded

Additional Resources

• Media:Mtk_packet_user_manual.pdf - Useful for understanding the various $PMTK commands that control our GPS.
• MTK NMEA checksum calculator

Projects That Use This Component

• Near Space Balloon