Re: [Paparazzi-devel] lisa has a different GPS interface?

[Tilman Baumann]

On 25/06/12 15:52, Marvin Wang wrote:
> hi Chris,
>
> i had tried that use ublox center in windows and it get lock within 1
> minute,(first time), but when it goes on my lisa/m2.0, it is another
> story. the GPS is very hard to get locked,  up to 10~20 minutes to get
> locked on my balcony.  in the field it takes more than 2 minutes. i
> dont know what causes this.

How is it if you power the Lisa board from USB?

I might have observed the same pattern. I have not looked much into it, 
but I had massive problems recently getting a stable fix. And the only 
change was that I used a UBEC to power the +5V line on Lisa.
I might need to clean that up a bit. I don't expect that UBEC to be any 
good (no name 3A 5V thing) but since everything it ought to power 
actually runs on 3.3V I thought it might not matter so much.
I thought the LDO will smooth that out. But perhaps they don't...

Can't prove those issues yet. Just want to mention since our experience 
seems similar.
Any tips what I should try to clean the power rail?

+5V is looped through a ferrite ring a few times.
Modem runs directl on 3.3V rail of Lisa. (could also hook it up on 5V. I 
soldered VCC behind the voltage regulator on the XBee breakout because 
this serial port was only 3.3V by default. But it's switchable)
uBlox MAX-6Q runs on 5V with it's own voltage regulator for 3.3V