Comment by Jhon on October 20, 2008 at 4:01pm

maybe good that antena to be used hidden inside a car, but for fpv, plane fly high, and the locosys gps is quite better, just 7 gr, and more tiny,
there is no need for a such good antena imo :P

Comment by Chris Anderson on October 20, 2008 at 9:40pm

The problem with the Locosys chipset is that it doesn't have a binary mode, so you've got to run an ASCII NMEA parser at 5HZ, which takes up a huge amount of processing power. I don't think we can do it with a single-core Arduino and still have enough power to do everything else, which is why we use binary mode on the EM406 and will probably do the same with the U-blox.

Comment by Genesis Factor on October 21, 2008 at 1:52am

annnnnnd it's sold out.

Comment by Koen Delvaux on October 22, 2008 at 1:59am

I'm also looking into a chip to embed on a dsPIC based autopilot board.
What I read on the Locosys website is that most of their chips do support UBX or sirf binary mode: http://www.locosystech.com/product.php?zln=en&id=1
If not, I have no problem in parsing NMEA in a few clock cycles on serial interrupt. Just do it one character at the time in a state machine. Only converting the ASCII to float takes some time, but then again the navigational computation is an order of magnitude more intensive so it doesn't really matter..

Does anyone have experience in obtaining a quote for these units in small volume? I doubt Digikey will carry them. Today I work with an old GPS mouse I had laying around for testing.

Comment by Chris Anderson on October 22, 2008 at 8:35am

The current Locosys GPSs (LS2003X series) are based on the MediaTek chipset, which do not support binary mode. The one you linked to is an older SiRFIII model.

But if you can write an efficient 5Hz NMEA parser we'd love to use it! We're tried most of the tricks, including serial interrupt, and it's still a bit of a processor hog.

Comment by Koen Delvaux on October 27, 2008 at 5:16am

I had to look for a bit where I could post the code for my NMEA parser, but here it is:

http://diydrones.com/forum/topic/show?id=705844%3ATopic%3A49807

Comment by Dean on October 29, 2008 at 3:10am

Locosystech (the company) sells Atmel GPS (Antaris 4 SuperSense) in same form factor as the little LS20033, and larger LS20031: http://www.locosystech.com/product.php?zln=en&id=15. I own 2 each of little LS20063 and the larger LS20061, though have yet to power them up. Check out Locosystech spec sheet for these at http://www.locosystech.com/download/module/LS2006x_datasheet_v1.0.pdf

Comment by Dean on October 29, 2008 at 3:17am

So... get the LS60033 and poof like magic you have what looks like LS20033 with the ceramic patch wanted by Jhon but Atmel chipset inside. Also, for those that want same form factor, Locosystech even makes SirfStarIII chipset GPS in their LS2002 series: http://www.locosystech.com/product.php?zln=en&id=4

Locosys does not = Mediatek by default.

I have EXTENSIVE testing of the 5Hz MediaTek LS20033 and LS20031 in AttoPilot... The larger LS20031 outperforms the smaller antenna version (LS20033) hands down in controlled experiments for solidity of GPS lock and retention of lock in steep banking turns (45+ degrees)... you only add 7 grams going from LS20033 (9g) to the LS20031 (16g). Key for both Media Tek units (and the ETek version) is smoothest possible power filtering to the GPS.. it is a serious requirement. Give this unit its own voltage regulator, and appropriate filter caps, and maybe even a ferrite toroid to wrap the GPS cable around 4x times.

Comment by jalves on January 6, 2009 at 4:56pm

Folks,
I have here a locosys LS20033 that I want to use to feed my osd applications with gps info.
I receive it today, connected to my pc serial port through a max232 interface.
the little receiver don't lock/fix sats, nor produce any nmea sentences. This is my first gps module receiver, so I don't know what to do with it.
Could the module be broken from the start? but minigps_1.32 show in it's first applet that it has no fix with the rest of the fields with zeros. the second applet don't show any sentences with nmea code, can I conclude that the module isn't producing any?
Sorry to bump in this blog, but after reading the entry above, I decide to ask you folks for your help and knowledge
Thanks In advance
JAlves

Comment by Dean on January 6, 2009 at 6:35pm

When I ordered multi-hundred Qty of LS20033 and LS20031, I got a test result sheet showing that each unit was tested and the lock time reported. All units are tested before Locosys sends them out.

The LS20033 defaults to 9600 baud, 8N1. I assume your max232 interface is setup for this?

First power up it might take many minutes to get a lock. In fact it could take 12.5 minutes to download the current ephemeris. Believe it or not, each satellite only sends data at something ridiculous like 50 baud (not 50k baud... thats 50 baud!). Part of the data message is ephemeris, and only a little at a time is sent from any single satellite. 1 sat can send entire epheris in 12.5 minutes.

What I do sometimes is put a 3V lithium CR123A cell on my GPs and let it sit with clear sky view for 20 minutes. The Locosys GPS in larger form factor (like LS20031) have a status LED that flashes when locked. even if it locks in a few minutes, let it sit for 15 or 20 minutes.

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