GPS receiver with external antenna? - Page 3

streets97f · 02-04-2008, 03:39 PM

I'm new to this forum and I've been trying to catch up on the discussion. From reading all the previous thread, I've got to say, that this Lassen DR+GPS idea is the best one since it's difficult to get the Ulbox unit. I'm very interested in bes51659's progress.

Did you order the Lassen module directly from Diamond Point? Should I just contact them to purchase or is there a retailer?

bes51659 · 02-05-2008, 04:30 AM

I ordered directly, see mail to you directly. There is Diamond Point in Sweden but for some reason they wanted to deliver from the UK.

Have you got a gyro? I seem to have been lucky to find one on eBay.

I have not got any of the components yet.

If someone else is interested I am willing to build a few units as long as I can get hold of gyros. Move fast.

-Stomp- · 02-05-2008, 09:24 AM

bes5165 -> Do your solution works, and can you share some pictures of it?

streets97f · 02-12-2008, 02:48 PM

stomp-->Bes5161 and I are still working on getting the parts bought and shipped. Hasn't been easy.

bes51659 · 02-12-2008, 04:14 PM

Sorry, I did not see your message. As streets97f says work is in progress. Gyro has arrived (only one), but the GPS receiver is far away. Hopefully there will be an adapter board with the gyro in place once we get the receiver.

Also I've ordered some BMW pieces friday. Shark antenna for TV, Radio and GPS, an antenna amp and some cables. Its gonna be neat! :-)

bes51659 · 02-16-2008, 04:56 AM

I've started on the pcb design. I've made my first library symbol in Eagle CAD

I am sure its got lots of errors...

The GPS receiver itself is due 21 march...

There is some confusion about how an active antenna is powered. (According to spec his lassen receiver require an active antenna and has powersupply for it??!?) Is it thru the standard SMB connector? If you've got some info, please step forward.

Me and street97 is also trying to get hold of higher quality schematics on how to interface the receiver than the one at the end of the dev kit manual. Q lies with Trimble right now (Thanks Richard of Diamond Point)

Again, help is apreciated.

bes51659 · 02-20-2008, 05:05 AM

In case someone is subscribed to this thread and worried that project has stalled... :-)

leeharper1 · 02-23-2008, 07:11 AM

Hey all...

I just used a haicom 204 and cut it open once out the case it splits into 2 bits one bit i put inside an aerial or could use a shark fin the other i put in a plastic hobby box in the roof lining.... job done gets a lock on 10 sats plus well happy

bes51659 · 03-11-2008, 05:28 AM

Marvelous! This would definitely saved me a bundle! I guess I am just a little bit vary of antennas and high frequencies and stuff. Too high respect.

Anyways. When I now realize dead reconning is within reach, this turned out to be a very educational project.

Work is proceeding. First parts has arrived. pcb will be ordered on monday. gps+dr will be available the 21'st. Total price of unit (including IBus interface for BMW and some other extras) will be something like €250. Excluding antenna. The IBus interface means that you do not have to connect tacho or direction to unit. It will get that info from IBus. But unfortunately IBus is only available on some BMW's. So there is tacho and direction inputs too, if needed later.

bes51659 · 03-23-2008, 08:19 AM

Ok, so PCB's are ordered at last!!

Unless there are problems I should have it in the mail by monday 31'st or April fools day.

I will start building two units to test first week in April.

Schmatics in earlier post is updated (in a minute)

bes51659 · 03-31-2008, 04:19 AM

I have got answers from Trimble about questions I've had. I thought that I'll share the answers in case someone else wants to build a GPS receiver. Cut from email conversation, but if you are really interested I think you will understand it anyway :-)

I got the answers thanks to courtecy of Richard Desfosse, Regional Manager Of Southern England, Diamond Point International (Europe)

**************************

Q1) Pin 14 is the reference voltage for the A/D converter, which converts the gyro output signal. It's always connected to the gyro supply voltage.
Q2) The Lassen DR-manual shows the suitable gyro rating for the given application circuit. It's actually not the input spec on the GPS-module itself. Lassen-DR "learns" the actual gyro characteristic and is continuously self-calibrating. But the x5 amplifier is needed for 2,5 mV/degree/s gyros in order to bring the signal into the optimal dynamic range.
Q3) The circuit of Trimble’s Starterkit board has several load options for different gyros with different supply voltages. NO_LOAD resistors are footprints on the PCB that are not populated with a resistor. They're open by default and 0-Ohm resistors could be assembled for different gyro versions.
Q4 Trimble say maybe you are right but, as long as the circuit works (which it does), it doesn’t matter.

Regards,
Mark Gurney
Technical Support - Diamond Point International (Europe) Ltd

1) Pin 14 is for the internal gyro circuitry – for your gyro it is 3.3V.
Q1) Just to be 100% sure: So I connect this pin to my 3V3 regulator? Not the 3.0V one that is supplying the gyro itself?
8) See last attachment. (schematics)
Q2) Since gyro is specified 2,5mV / degree / s and input of GPS is the same. I do not understand the x5 amplification on your adapter board. That gives 12,5mV from the gyro, doesn’t it?
Q3) What is NO_LOAD resistor? I use Epson XV8100. Should I put an actual resistor into my design?
Q4) Seems to me the filters on the diff amp stage is not symetric on vref and vout intput. And impedance is not balanced either. Am I wrong? Are maybe noise and output impedance of vref and vout not symetrical?

Thanks, BR, B-O Swing

2) Yes. Pin 1 has a square solder pin. Top row will be odd, bottom row will be even.
3) Leave floating
4) Pin 14 is for the internal gyro circuitry – for your gyro it is 3.3V.
5) Yes
6) Ask Epson – its their part
7) Trimble 5V antennas have a voltage range of 5V +/- 0.5V. So 5V should be fine
8) See last attachment.

Mark

1) Can I leave pin 1 unconnected? (I think so) (btw. I have not found how the contact is numbered! Can you tell me how you’ve numbered it?)
2) Can I leave pin 11 unconnected? Reset input should probably be pulled-up or grounded.
3) What is pin 14?Input gyro voltage??? I guess it is just to connect it to 3,3V
4) Is direction high = reverse?
5) Epson gyro is 3.0V +-0,15V. My regulator is at 3V3. I guess I need a germanium or schottky diode maybe to lower voltage-But since the Epson XV-8100 is on list of supported devices I am just a bit suspicious that a spec might be wrong. Please confirm.
6) feed of 5,5V to active antenna. But input voltage is specified as 5V... Is there a buck boost or something internally on the module?
7) I need a better version of the schematics in order to see filter component values etc.

BR, B-O Swing

Attachments:

dev kit schematics (high resolution)
App Note 1
App Note 2