SparkFun Forums

[Muris]

Hello everyone,

My Venus GPS chip is a little bit warm when operating. I read NMEA data correctly but I didn't get the GPS fix yet - I have tried it only in my room.

So, does your chip get a little warm on 3.3V ?

Thanks in advance,
Muris

[corvette123]

try it outside?

[Muris]

Well, I was afraid that something was wrong because it gets warm, so I turned it off to prevent damaging

It draws around 95mA (including LED and LNA) and tomorrow I will try it outside. I hope it works because it would be a shame that this project goes to trash.

Check it out: http://www.elektronika.ba/gps_car_venus634.jpg

[e-shepherd]

wow..nice.. hope you get your fix.. i think it draws about 70ma in tracking without LNA

[Muris]

I just got PM from "gm" and it seams that everything is good. It should get a little bit warm during acquire.

Now I just have to go out and try it

I also noticed that I left pin 8 unconnected as they did in datasheet for this chip, but it turns out that this pin is used for selecting the "acquiring" method. Anyway, it *should* also work as it is

Mure

[e-shepherd]

goodluck, let us know how it goes

[BrianS]

Mine works very good. Acquires sats within 30 secs. I put my finger on the chip and didn't notice it getting hot or even warm. Running mine off a Lipo battery. I took mine on a 30 mile drive and logged the position data. Took that data into Google Earth and mapped it. Accuracy is very good was within 3 meters at standing still. But will drift somewhat to maybe a max of 10 meters.

Bryan

[Muris]

Hello,

I can't get the satellite fix

I have tried these combinations:

1. LNA + Chip antenna
2. LNA + Ceramic antenna
3. Only ceramic antenna

It just doesn't want to work

What was your configuration? Bought already soldered module or just a chip like I did?

Btw, what version is your SkyTraq software, mine is 0.4.413?

Muris

[BrianS]

Got mine with an SMA connector on board and memory too from SF. Hooked up an mobile antenna (has a built in LNA) and works on 3.3 volts.
Had now problems getting a fix. Even worked indoors when I placed the antenna near a window. Had to angle it a bit to point to the sky but did acquire sats and got a fix. I would if you just have the chip recheck all your connections, get a good mobile antenna (3.3 volts). SF has them.
I've run the same version software and have not had any problems communicating with the GPS. I used the a serial to USB chip to interface it.

Bryan

[rtaubitz]

Could it be because you haven't connected the RF Ground pins? How close is the RF trace's to 50 Ohm? What does that chip do on the RF line? The Venus has a built in LNA, you just need to inject 3.3v in to provide power for the active antenna.

You can use http://www.cepd.com/calculators/microstrip.htm to calculate the required width of the RF strip to get 50 Ohm.

[leon_heller]

I can't see it working with that piece of track as an antenna. You need a proper active antenna with 50 ohm microstrip connecting the cable to the chip input.

Leon