by

|   November 10, 2008 at 5:33 PM

Do you have a connector for it.
Can you set it up with SirfDemo or another program.

by

|   November 10, 2008 at 8:25 PM

The pads on back are 0.1" spaced, and 2 of the pads are redundant GND, only 1 needs connection. Conveniently you can solder a 4 position strip of 0.1" header pins to it. You can also simply strip ends of wire and solder them direct. Very easy with 0.1" spacing.

With SAW filter, LED status, built in RAM backup super cap, and slight lower mass, and same command set as EB-85A, this unit is by far my preferred choice over the ETek unit.

If you make a serial connection to your PC, you can use the same media Tek PC programs that Saprkfun has on the page for the EB-85A (Mini GPS, GPS locator utility.)

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|   November 11, 2008 at 2:36 PM

Thanks Dean,
I soldered the wires directly to the pads.
everything works great.
Alex

by

|   November 13, 2008 at 11:09 AM

How would you expect the accuracy of this module to compare to that of the GS405?

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|   November 14, 2008 at 9:02 AM

That's a really hard question to answer. Both LS20031 and GS405 have very good sensitivity, but the antennas are fundamentally different. GS405 should perform better where you are unsure of the eventual orientation (backpacks, pockets, etc). The LS20031 should have better performance where you have a clear, stable view of the sky (UAV, AVL, tracking, etc). If you need more GPS data, the LS20031 is 5Hz where the GS405 is 1Hz.

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|   November 14, 2008 at 5:12 PM

Comparing the LS20031 to a EM-408 sirf3, in my house the LS20031 will get a good lock (8 sat’s) where the EM-408 will not lock at all.
Will you be offering the LS20033 soon?

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|   November 16, 2008 at 5:39 AM

Hello,

What is the input voltage range? please


Thanks

by

|   November 17, 2008 at 8:52 AM

Page 10 of datasheet. LS20031: 3V to 4.2V(max) 3.3V typical. I'll post to description as well.

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|   November 17, 2008 at 11:37 AM

How does this compare to the FV-M8 you carry? That's a big price difference.

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|   November 21, 2008 at 2:19 PM

This module is on par with FV-M8 (formerly the EB-85A) module in terms of protocol, sensitivity (tested both modules indoors in the basement) and functionality (minus a second UART RX/TX pins of which wasn't useful on the EB-85A anyway).

The two really nice features that this GPS module has, compared to the FV-M8, is a battery to preserve GPS data and quite a bright red LED that blinks once per second upon fix. Not to mention the big price difference.

It is more convenient to use without requiring a special cable and connector (or a break out board) as others have mentioned about it. Overall I see it as a great replacement/alternative for the FV-M8.

Now there is one interesting difference from this module and the FV-M8 is that there is no EMI shield housing the components. Not sure if that will effect or matter to anybody else in terms of quality of the module because so far I've seen nothing wrong with the LS20031 module.

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|   November 18, 2008 at 11:27 AM

The datasheet does not mention SiRF Binary mode at all, does this module support it?

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|   November 27, 2008 at 1:17 AM

My unit defaulted to 57600 baud. How can this be changed?
Also, how do you enable/disable DGPS/WAAS? Locosys data sheet is pretty thin. Has nothing at all about inputs.

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|   November 28, 2008 at 11:41 PM

You can change to 34,000 by sending this command: $PMTK251,38400*27

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|   November 28, 2008 at 11:43 PM

Of course I meant 38,400!

Also, you can turn on 5Hz mode with this: $PMTK220,200*2C

And turn off all but the GGA and RMC NMEA sentences with this: $PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*28

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|   January 18, 2010 at 0:50 AM

PMTK220,200 made the difference for me :-). I wonder why that command isn't in the list on the PMTK Protocol Reference linked to here...? Weird.

(For reference, the '200' at the end there means milliseconds between sending data back. default for mine was 1000=1hz)

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|   December  7, 2008 at 6:19 AM

Does anybody have an eagle footprint for this? From the picture it looks like you could put some right angle headers on it, and use some stand-offs to keep it hovering above the PCB? (I'm Ron Burgandy?)

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|   December 27, 2008 at 5:15 AM

Hi guys, I noticed that this Gps module says it has a TTL serial inetrface whereas the FM-V8 has an NMEA serial interface. Could some one please explain the difference as i do not have much technical knowledge and if either can be used with most boards/ autopilots

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|   January  7, 2009 at 1:06 AM

Hi HS,

TTL is hardware (signal level logic), and NMEA is software (NMEA protocol). The NMEA data is provided on a TTL serial port.

Antoine

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|   October 19, 2009 at 10:51 AM

can I know if the gps ls20031 can communicate directly to a microcontroller via uart?

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|   January  1, 2009 at 2:39 PM

This thing works great. I'm in my basement workshop and can receive a solid signal from 7 satellites. I have a few other GPS receivers, and none of them can get a lock while in the house, not to mention in the basement.

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|   January  1, 2009 at 3:40 PM

This thing works great. I'm in my basement workshop and can receive a solid signal from 7 satellites. I have a few other GPS receivers, and none of them can get a lock while in the house, not to mention in the basement.

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|   January  6, 2009 at 4:49 AM

Hi guys,

A very simple question (but probably quite hard to answer):

Is it a true 5Hz update rate GPS (I mean not extrapolated) ?

I've been testing a few GPS sensors, from fake ones to good ones, but I haven't tested this one yet.

For example the EB-85A is not a true 5hz GPS and has a horrible latency. In fact, to reduce the position noise, it has a low pass filter on the accelations, which makes it good when translating smoothly (car application), but unusable on an airplane/helicopter.

The only good one is the Ublox5 GS406 with a real 4hz update and a very good configuration tool (u-center). You can specify the filter parameters (<1g, <2g, <4g accelerations for example) But it seems to not be in stock anymore...I luckily could buy one when it cames out.

So, has anyone check the latency/reactivity of this GPS.
The test is simple: At T0, start running in one direction. Measure the time T at which the GPS moves. T-T0 should be less than 300ms.

Subsidiary question :
Is the GPS velocity calculation based on doppler effect (of the carrier) or derivative of the positions?

Thank you, and have fun.
Antoine

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|   October 15, 2009 at 11:03 PM

I second this, maybe my understanding differs but the description states "...one-second navigation update..." Does this mean it communicates at 5hz but only updates position, speed, ect, once per second?

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|   January 15, 2009 at 1:26 PM

I connected the chip to my mikroe developement board. I think it connects at 57600. But I get very strange characters. I tried other rates but then it does not work. How can I check the actual output baudrate of the device??

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|   January 19, 2009 at 10:49 AM

Is there a programmer reference or user manual that defines the $PMTK configuration strings for LS20031 ?

by

|   January 19, 2009 at 12:21 AM

Yup, just posted:

http://www.sparkfun.com/datasheets/GPS/Modules/PMTK_Protocol

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|   January 19, 2009 at 4:14 PM

Jordi's example on DIYdrones shows $PTMK220 and $PTMK251 commands that aren't in the Etek document you referenced, though $PTMK314 is shown.

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|   January 20, 2009 at 8:22 AM

I just got this from Locosys. It would be nice to see the complete manual from which this info was extracted, but at least this is a starting point ...

========================================

Packet Type: 390 PMTK_API_SET_USER_OPTION

Packet Meaning:

API_Set_Flash_User_Option

Write the user setting to the flash to override the default setting. Maximum 8 times without erase the chip.

DataField:

PMTK390, Lock, Update_Rate, Baud_Rate, GLL_Period, RMC_Period, VTG_Period, GSA_Period, GSV_Period, GGA_Period, ZDA_Period, MCHN_Period, Datum, DGPS_Mode, RTCM_Baud_Rate

Lock: nonzero: freeze the setting; 0: allow further setting

Update_Rate: 1~5 (Hz)

Baud_Rate: 115200, 57600, 38400, 19200, 14400, 9600, 4800

RTCM_Baud_Rate: 115200, 57600, 38400, 19200, 14400, 9600, 4800

XXX_Period: NMEA sentence output period

DGPS_Mode: 0 (disable), 1 (RTCM), 2 (SBAS)

Datum: We support more than 200 datum. Please refer to Appendix A for the supported datum list. The typical value is: 0 (WGS84), 1 (Tokyo-M), 2 (Tokyo-A)

Example:
$PMTK390,0,5,57600,1,1,1,1,1,1,0,0,0,2,9600*04

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|   February  6, 2009 at 1:32 PM

I was wondering if there is a way to turn off the indicator LED via software? The documentation doesn't seem to mention this.

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|   February 21, 2009 at 5:26 PM

After some diligent searching, I found this link to a more (if not wholly) complete Mediatek $PMTK command reference.

Download it while you can..... =:-)

http://www.rigacci.org/wiki/lib/exe/fetch.php/doc/appunti/hardware/gps/mtk_nmea_packet_0.8_transystem.pdf

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|   February 25, 2009 at 12:11 AM

So can i connect this gps to the ftdi basic breakout board and connect them to to a hyperterminal and see the nmea data ? what should be the hyperterminal settings?

I have this unit and want to test it out first.

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|   February 25, 2009 at 7:39 PM

I soldered a 0.1" right angle header to the pads on the GPS board (similar to Digikey #A28770-ND) then plugged into my microprocessor interface (Rabbit RCM2200 makes it easy). A bit of double sided foam tape to hold things in place - and you're in business.

The unit I received, was programmed for 57600 bps out of the box - despite what the spec sheet says. Set your serial port up for 8 bits, No parity, 1 stop (8N1).

I was able to set up for slower bit rates, but because of the sheer number of NMEA sentences generated at the 5hz update rate, bit rates slower than 38400 generate a PMTK_ACK message that says the baud rate command was 'valid but action failed'. 115200 bps worked fine as well. I suspect you can slow down the baud rate if you turn down the position fix rate and turn off the NMEA sentences you don't need/want to use.

To see a more complete reference to the control commands, see the PDF link I posted above.

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|   April 12, 2009 at 9:54 PM

i've just recently started prototyping with this gps unit, so thanks to everyone who has posted information.

just so others know, the default for my unit was 57600bps, 5hz output. I was able to lower the baud rate to 4800 only after I reduced the output to 1hz.

Does anyone know what the best setting for DGPS_Mode should be, or at least what it depends on? If RTCM, how does RTCM baud rate fit in? (or are they unrelated)

Also, I am a bit unsure of what "API_Set_Flash_User_Option" does. Is it used to set the default settings, so a reset to default using "$PMTK104*37" would reset to the settings I set with "API_Set_Flash_User_Option"

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|   May  1, 2009 at 8:18 PM

API_Set_Flash_User_Option: Sets the default power-on settings of the unit - assuming total disaster (batcap dies). I would be tempted to leave this alone as the unit will remember settings last set (until the batcap dies). There are only a certain number of times your can store the "User_Option" before needing a "reset" of which I have not been able to find a method. Sort of like the maximum number of times you can set the "region code" of a DVD player before you can't set it no more.

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|   April 29, 2009 at 7:40 PM

what is the command sequence to lower the chip to a 4800 baud? I can't seem to get anything to work... I can't even figure out how to change the refresh rate.

Thanks.

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|   May  1, 2009 at 8:36 PM

Take a deep breath. Relax. Think "clear blue ocean... clear blue ocean..."

See Zlite's comments from 28-Nov-2008 above for setting baud rate and sentence rate.

First thing to keep in mind is that you will have to set the sentence rates and quantity to less than 5Hz before you can successfully set communication at 4800 baud. The sheer quantity of data at 5Hz is faster than 4800b can deliver before the next fix update is ready.

The sentence setting commands are easy enough to build, but you will need to construct them with proper checksums - which I assume you know how to do. There is guidance available from code at the DIYDrones link above, or I can post C code to get you over the hump.

Please also see
http://www.rigacci.org/wiki/lib/exe/fetch.php/doc/appunti/hardware/gps/mtk_nmea_packet_0.8_transystem.pdf as it is a more complete reference that Sparkfun posts here.

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|   May  2, 2009 at 5:21 PM

Below is a quick code snippet to compute the checksum of any given NMEA sentence, and a function to construct a complete NMEA sentence - once you have the checksum.

#define CH_CR 0x0D
#define CH_LF 0x0A

const char CRLF[]={CH_CR, CH_LF, 0};

char *NMEA_ComputeChecksum(char *s)
{
static char ck_string[4];
static unsigned char chksum;


for(chksum=0; *s; ++s)
chksum ^= *s;

sprintf(ck_string, "*%02X", chksum);

return(ck_string);
}


char *NMEA_ConstructSentence(char *s, char *msg )
{
strcpy(s, "$");
strcat(s,msg);
strcat(s,NMEA_ComputeChecksum(msg));
strcat(s, CRLF);

return(s);
}

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|   May  2, 2009 at 5:32 PM

So the short answer to your original question - 'what is the command to set 4800b' - is "PMTK251,4800".

That assumes that you are already communicating with the GPS module at some established default rate - which in the case of this module is 57600.

The paradox is that if the new baud rate is sucessfully set on the module, you will need to reset the rate on your serial port - so success is indicated by NOT being able to read the acknowledgment sentence "PMTK010,001" (or "$PMTK010,001*2E" in complete NMEA format.

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|   May  2, 2009 at 5:39 PM

Now - as has been indicated previously, you will NOT be able to set such a slow baud rate, until you slow down the frequency and type of NMEA sentences being sent from the module.

This is done by using the PMTK314 command. Not to be so smug - RTFM! =:-)

For experimental purposes, an example configuration sentence to set that only GPRMC sentences are to be sent at 1hz: (which should slow down and simplify things considerably)

NMEA_ConstructSentence(buf,PMTK314,0,5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0");

How's that??

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|   May  3, 2009 at 10:14 AM

So the complete sentence to send only GPRMC sentences at 1Hz is:

"$PMTK314,0,5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*2D"

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|   May  2, 2009 at 7:05 PM

PMTK251,4800
but with *xx cr lf added on

Now the dumb question, what is the checksum byte ??
I have no way of calking it !(within reason)

by

|   May  2, 2009 at 10:21 PM

The checksum is a simple calculation that you can do with the help of Google:

Try this Web App: http://www.hhhh.org/wiml/proj/nmeaxor.html

BTW, I don't think appending the checksum is necessary. Try it without if you want, especially if your doing the setup manually.

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|   May  3, 2009 at 10:12 AM

So the short answer would be...

"$PMTK251,4800*14"

by

|   May  5, 2009 at 3:54 PM

I don't know what is wrong with my LS20031. It was getting a fast lock the first days that I had it, but now I can not get a lock anywhere. The red light blinks once when the power is turned on and that is it.

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|   June  8, 2009 at 2:21 AM

Hi ThomasFletcher,

Did you find out why your GPS couldn't lock anymore ?
My unit seems to follow the same scheme : first days it was locking 8 sats indoors, and now I have to go outside and wait 15min to get 3 sats.
And when I move few meters around my position, the signal disappears !

I don't know what to do...

by

|   May 13, 2009 at 10:46 PM

Here's a handy note...

If the unit gets into an unknown state, (i.e. you forgot the baud rate) try disconnecting the unit, and short out the battery terminals for just a second. That will bring the unit back to it's default state. (57,600bps and all the sentences).

Note that that's awful for the battery, will void warranties, and stress the space/time fabric of the universe, but it works.

Don't ask me how I know this. I didn't just spend a whole day on this.

-Dan n7nmd

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|   May 17, 2009 at 4:27 PM

Anyone know if this does or does not have the altitude lock-out?

Thanks!

by

|   May 21, 2009 at 7:38 AM

Forgive the question, but what do you mean by "altitude lockout"? Do you mean a forced 2D fix mode?

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|   May 25, 2009 at 4:34 PM

A lot of GPS manufacturers impose performance limits on their receivers, supposedly to stop them being used in missiles. The two most common limits are:

1) Altitude limit of 60,000 feet
2) Speed limit of 999 knots

The can sometimes be an "or" limit (i.e. stops working when either of the limits are reached), or an "and" limit (both limits much be reached before it stops working).

Obviously for high altitude projects the altitude limit can be met, but it's not common for hobby projects to reach the speed limit.

I emailed the manufacturer and got back from them...

"This is Eric Chin from LOCOSYS Technology Inc.

Thank you very much for this email and using our product.

All commercial GPS module has altitude limitation, 60000 feet. If the module over the altitude specification, it will not get position immediately. "

Interperet that as you will...

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|   June  3, 2009 at 10:52 PM

Sparko4Marko: So the complete sentence to send only GPRMC sentences at 1Hz is:

"$PMTK314,0,5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*2D"

Thanks, works here !

by

|   July 13, 2009 at 9:09 PM

From a little testing with a multimeter here the module will use up to 60-70mA at startup and 35-50ma (avg. ~45mA) once it has a fix.

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|   August 10, 2009 at 9:56 AM

As for the 221 command that someone posted, I found this document from another device that documents the 221 command:

ftp://ftp.leadtek.com.tw/gps/9023/LeadtekNMEAProtocolManualforMTKV1.0.pdf

PMTK221,RunDuration,RunInterval
RunDuration: Duration [msec] to fix for (or attempt to fix for) before switching from running
mode back to a minimum power sleep mode.
`0': Disable
Flag:
>=`200': Enable
RunInterval: Interval[msec] to come out of a minimum power sleep mode and start running
in order to get a new position fix.
Some restrictions for the parameters:
(1) RunDuration >= 200 ms
(2) RunDuration <= RunInterval
(3) RunInterval <= 86400 ms
Example:
Fix 5 seconds and then sleep 5 seconds periodically
$PMTK221,5000,10000*07

by

|   August 10, 2009 at 10:09 AM

Uh, the comment system ate some of the brackets. Sorry about that.

by

|   September  6, 2009 at 9:26 PM

Took me a while to figure out how to configure this with OS X, so I figured I'd document the process here for quick reference for anyone else needing the information

-Open Terminal (/Applications/Utilities)
-If you don't know the /dev entry for your serial communication device, with it disconnected type "ls /dev/tty.*"
-Now connect your serial communication device, and enter the previous command again
-The /dev entry for your device should be the only new entry
-With your serial device connected to your computer and GPS module, type this line in Terminal (replacing "" with the real /dev entry):
screen -L 57600
-The hard part for me was sending the CRLF sequence after each sentence. The best way I found to send this sequence is to use screen's command line mode by pressing ctrl+a, and then : (colon)
-Enter your sequence using the following format (obviously replacing "$PMTK000*32" with the appropriate sequence. The "$" character needs to be escaped and the "1512" sequence will be converted to the CRLF sequence):
stuff "$PMTK000*321512"
-Then just press return to send the sentence

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|   September  6, 2009 at 9:31 PM

Ugh. The page mangled my post despite the "preview" displaying correctly. Let's try this again:

The sample sequence should be:

stuff "\$PMTK000*32\015\012"

by

|   September  6, 2009 at 9:34 PM

Yup, that did it. "\015\012" gets converted to the CRLF sequence

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|   September  6, 2009 at 9:43 PM

Oy. Didn't notice that the Terminal command to start screen also got mangled. It should be:
screen -L [your /dev entry] 57600
Replacing "[your /dev entry]" with your actual dev entry.

Sheesh. Where's the "edit" button for these comments?!?!

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|   September 14, 2009 at 4:02 PM

Just a note to buyers - these are not pristine, new GPS units. I think they are stored in some kind of tub or something, my unit was scratched on the top and had smudges on it.

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|   September 14, 2009 at 8:28 PM

I would like to connect a LS20031 (3.3V levels) directly to the RS232 serial port on my PC (then I can directly see the data by running a comms program in the PC). Is there a converter gadget available to do this? Does Sparkfun sell such a gadget?

I would also like to connect the LS20031 to a USB port (for use with a laptop that has no RS232 serial port) -- is there a converter available for this, and does Sparkfun sell it? Does it come with software to allow serial comms programs to operate via the USB port?

Cheers
C

by

|   September 14, 2009 at 8:32 PM

The LS20031 has a "Built-in micro battery to preserve system data for rapid satellite acquisition". What charges the battery? (is it charged from Vcc?) What happens when/if it goes flat?

Cheers
C

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|   October  9, 2009 at 10:24 AM

Just to be sure, the communication protocol is USART for LS20031? Thanks.

by

|   October 19, 2009 at 4:17 PM

Correct, the LS20031 communicates via 3.3V TTL level USART.

by

|   October 31, 2009 at 7:35 PM

I would like to buy one of these, but reading the features I am slightly confused... It says it communicates at 57600 bps but it also says "one second navigation update..." does that mean that this updates once per second but communicates at 576000 bps?

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|   November  5, 2009 at 4:28 PM

Scotty,

Yes, the default UART communication rate (despite the documentation) is 57600. This rate can be made slower via commands (to rates as slow as 300 Baud - I think).

The fix update rate can be made as slow as 1 per second and as high as 5 per second (default) via command.

However - with the fix rate at 5 per second, the slowest UART communication rate that can be set is 38400 because there is too much information to transmit (if all the sentence type are turned on - which is the default) before the next fix is ready to be sent.

Bottom line, you can slow down the communication rate, but you also have to either slow down the fix rate - or - turn off sentences that you don't need - or - both.

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|   December  2, 2009 at 4:10 PM

Latency - I have used the LS20031 in my autopilot products for over 1 year. I recently measured the heading latency by comparison of differentiated GPS heading (dHead/dt in deg/sec) against the same data directly from the IMU. The lag measured as 1.4 to 1.6 seconds on a day with 7-9 sats in lock during the flights.

by

|   December 28, 2009 at 12:07 AM

How does one solder this to a PCB? From the picture the bottom doesn't look flat, with all the chips there? Also the pads dont seem to too accessible for an iron . . .

by

|   December 30, 2009 at 1:34 PM

TDMA,

For the connection, I have used a common right angle header strip - broken off to 5 pins, then soldered to the pads on the unit.

For mounting, there is always double sided tape, stuck to the processor shield, then to the PCB (crude, but effective). The "proper" way would be to use stand off posts in the corners and fasten to the PCB - or make a square hole for the antenna, then fasten directly to the PCB.