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U-blox 5 GPS - no satellites (no fix)


#1

Hi,

I got a ublox 5 GPS unit the other week and I’ve been trying to get it work for days, but to no avail.

I was wondering if anyone could give me some tips or advice on what I am doing wrong.

I am using the Sparkfun breakout (GS407) to connect the u-blox to a FTDI cable (Thanks MarkH). and powering it with clean 3.3v.

I used the u-center software to connect to the device. I get the following messages from the GPS unit (all the time):

But this is all I get.

These are the things I have tried:
[ulist]
Flashed the module with the latest firmware
Powered the 3.3v from a Fez Panda
Powered the 3.3v from a 3.3v voltage regulator
Added all the filtering capacitors they suggested
Reset the module back to default settings
Stood outside with it for 20 mins (clear sky)
[/ulist]

I have heard that the module requires a good clean 3.3v, so I tried all the options I could. I noticed a voltage drop of 3.1v across the module when it is running, even though I supplied it with 3.3v - Not sure if this helps.

I haven’t powered it with anything but 3.3v, so I’m quite certain I haven’t fried it.

Any suggestions would be really appreciated. Thanks.


#2

If you’re getting voltage drop, it could be there isn’t enough power coming out of the regulator. Do you have a regulated lab supply, or an old PC power supply you can take 3.3v from? 3.3v from the panda should be more than enough though =\ The IC package they have on there should handle 750mA or so and this will only use 75ma…

Make sure all your grounds are connected to a single point.

I haven’t looked at the datasheet for awhile, but perhaps try to send it a config sentence (change the update rate or sentences that get sent).

Hook VBatt directly to your 3.3v supply, dont worry about the coin cell.


#3

According to the data sheet it works from 2.7 -> 3.6v so that can’t be it…

Is it a TTL connection ? some time they are inverted!!

What interface is it? You may need flow control!!

Ian


#4

If you are receiving messages, such as you are, then the power voltage and connection to the FEZ most likely fine.

You are not getting any time data, so you are not receiving any satellites.

If you took it outside, and did not receive good data, then I would check the antenna connections.


#5

The format of the NMEA sentences seems correct and the checksum is fine. But what is the ??.??.?? in front of them?

[edit] I see that the ??.??.?? is some sort of timestamps from the software, I’m used to just looking at it in a serial terminal :slight_smile:

As Mike said, take outside and check the antenna connection. Everything else seems fine. From a cold start it can probably take several minutes to get a fix.


#6

Thanks for all the replies.

The module takes a TTL connection, and from other people’s posts and from the manual, it doesn’t say anything about flow control.

From what I can see the Antenna is securely on with 4 big blobs of solder.
I tried moving it around when I was outside, but still no satelittes.

Here’s what I’ve done from your suggestions:

  • Connected the BATT pin to 3.3v
  • Check the current it is using: 70mA to 110mA
  • Confirmed all GND points are grounded
  • I updated the almanac for the next few days

So after these changes I went outside for about 15 mins - Not one satellite is in range.

I tried another GPS module I had, and satellites popped up within a few seconds.

Some thoughts:

  • Perhaps the connection to the antenna is faulty - but I can’t check that as it is all enclosed.
  • Perhaps I’m still not getting the voltage right - It’s strange that the voltage drop is only 3.1v instead of 3.3.
  • Perhaps it’s got something to do with me being in the southern hemisphere, whereas the module comes from the North.