Hi, On Mon, 28 Apr 2008 19:53:34 +0100 Andy Green <[EMAIL PROTECTED]> wrote:
> -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Hi folks - > > While trying to make DM2 GPS work good, I became annoyed at the range > of behaviours the GPS unit and finally spent the whole latter part of > the day meddling. I don't think I found where the problems came > from, but I found something that is less good than it should be. GPS > stopped working altogether on my boards at the moment (unrelated to > ripping the cans off the GPS section I believe) so I don't know where > I got to. ah, that shield is quite stubborn. > specifies low level input selecting "OUTPUT" 2 is min -200mV, typ 0 > and max 200mV. The other active level is specified min 2.7V, typ > 2.8V, max 3.0V. So you have to drive that chip hard to 0V or the > power rail to select either input. > > But at our normal situation with internal antenna and no load on > external antenna, we drive VCONT to 810mV (26% Vdd). That might explain some of the things I've been seeing here, bad reception with the internal GPS antenna and maybe the failure of the antenna switch on my v4 was a result of this floating (or the tolerance just changed resulting in really bad reception). One more thing, don't know if it's related. In the Antaris 4 System integration manual which you can find here: http://www.u-blox.com/customersupport/antaris4_doc.html Near page 77, ff. is the antenna short circuit protection described. Now when I power up my Neos GPS it spits out the following messages: $GPTXT,01,01,02,ANTSUPERV=AC SD OD PDoS *0A $GPTXT,01,01,02,ANTSTATUS=SHORT*6D If you read the manual you will notice, that AC: Antenna Control, antenna will be switched on/off by the GPS SD: Short circuit control enabled PDoS: Power down antenna if short circuit is detected And now of course ANTSTATUS=SHORT, antenna short circuit has been detected. Okay, I just had a look in the ATR635 Manual and it says to just leave pins ANTON, ANTSHORT_N and AADET_N unconnected if we're not using it which is what we do. I guess we can ignore the messages, though I'm not 100% convinced yet. :-) Regards, Daniel Willmann
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