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Tips and questions relating to the GPS modules from SFE
By fatal1ty89
I need a GPS receiver to use in robotic applications.
But I'm confused, there is too many receivers; :roll:
I'm thinking to buy Em408 or LS20031.
can you help me to decide?

Em408 :
+Optional antenna

LS20031 :
-/+(?) Chip antenna (can we plug an optional antenna?)

Which one do you recommend?

Thanks in advance...
Last edited by fatal1ty89 on Sun Jan 04, 2009 6:47 am, edited 1 time in total.
I haven't personally used the Em408 so I cannot comment about it specifically, but couple of a weeks ago I did get a hold of the LS20031 and its really nice.

LS20031 does not have an external antenna connector like many common GPS modules do since it has an onboard antenna, so you're stuck with the onboard antenna in that case. Although there is nothing wrong with the antenna it uses unless you are putting the LS20031 module into a metal casing to house along with other hardware components and in that case then it does make it a downside to using it.

Also note that the LS20031's UART pins are TTL level which means you can directly connect the GPS module to a micro controller without anything else required as long as the micro controller its self doesn't use a built-in line driver on its UART pins. Now if you're wanting to connect the GPS to your computer you will need to interface the UART pins coming off the GPS module to a line driver or a RS232 Shifter module and then connect your computer's UART cable to that for example.

I have seen somebody mention that the LS20031 does not appear to support the SiRF binary protocol. Just the standard NMEA 3.01 ASCII sentence protocol.
By fatal1ty89
I get my LS20031, Now I'm trying to communicate with hyper terminal,
I'm setting the baudrate and comport but the receiving datas are meaningless.
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In GPS datasheet baudrate indicated as 9600, I tried 9600,2400,4800 19200 vs. But nothing changed.

Gps TX 3.3v, my rs232 converter is 5v, but 3.3 is logic 1 for 5v.

What you recommend? What I should do?
Thanks in advance..
By gussy
Most of those baud rates you listed are too slow, 5Hz GPS's need quite a bit of bandwidth with all the extra NMEA data over a 1Hz GPS.

It says on the Sparkfun product page 57600bps, which is usually the most common for the MTK chipsets.

You really should be using a level converter too.
Please try this configuration to see if you get valid data:

Bits per second: 9600, 19200, 38400, 57600, 115200 (try each one)
Data bits: 8
Parity: None
Stop bits: 1
Flow control: None

For me my LS20031 came up as 38400 baud by default and I'm currently using 57600 baud for maxing out the 5Hz of which appears to have no issues as there should be plenty of bandwidth. Also make sure to use a serial cable no longer than six feet in length between the computer and RS232 converter / line driver that is connected to the GPS module.
By fatal1ty89
Thanks for your response MR. Tron.
You're right, my gps baudrate was 57600 and in 5hz mode however datasheet indicating 9600baudrate :)

How can you use your gps modules in software? I'm using C# and I can show the coordinates in Google Earth, but I can't draw the line of GPS way, have you tried to draw a line like that?
By olivier_p
You can make your C# application read the serial port. You'll then have to parse that string to get the numerical value of each of your parameters (lat, lon, etc).
By fatal1ty89
olivier_p wrote:You can make your C# application read the serial port. You'll then have to parse that string to get the numerical value of each of your parameters (lat, lon, etc).
Thanks, I have already get lat and long but, I want to draw the line of lat/long points...