gta02-core and external GPS antenna

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gta02-core and external GPS antenna

Werner Almesberger
There's one simplification that looks attractive to make in gta02-core
and that's to remove the external GPS antenna connector. From what I've
heard, this antenna is rarely used in the FreeRunner, and for
stationary use, one could connect an external antenna to the socket for
the internal antenna.

There are the following benefits in removing the external antenna:

- reduced SMT cost by removing about a dozen components, some of them
  unique. Due to its shape, The antenna connector may also need
  special treatment in SMT, such as glueing.

- fewer components means less risk of getting interferences. This goes
  particularly for the external antenna socket when open.

- simplifies the layout of the GPS RF circuit and thus reduces the
  risk of us getting something wrong.

- when investigating the SD/MMC vs. GPS problem, Andy found that the
  antenna selection circuit is operating with an incorrect voltage.
  Apparently, this didn't cause any observable problems, but then
  you never know what's really behind the occasional glitch ...

- in case future designs are made based on gta02-core, a smaller GPS
  subsystem may allow for a smaller PCB size or give more room to
  other subsystems

There are also a few disadvantages:

- if you really need the external GPS antenna along with the internal
  one, this will not be a welcome change

- the antenna connector also helps to hold the PCB in place. Without
  it, there is only USB on that side of the board to assist the
  snap-in mechanism. (Probably doesn't matter all that much, though.)

- removing the connector leaves an empty hole in the case

I think the benefits outweigh the disadvantages, so I'd like to see
the external GPS connector gone.

Any thoughts ?

- Werner

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Re: gta02-core and external GPS antenna

H. Nikolaus Schaller

Am 28.05.2009 um 21:53 schrieb Werner Almesberger:

>
> - the antenna connector also helps to hold the PCB in place. Without
>  it, there is only USB on that side of the board to assist the
>  snap-in mechanism. (Probably doesn't matter all that much, though.)
>
> - removing the connector leaves an empty hole in the case

There are some requests for a 3.5 mm Headset connector...

Maybe one variant could have both, 2.5 + 3.5 mm

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Re: gta02-core and external GPS antenna

joakim
In reply to this post by Werner Almesberger
Werner Almesberger <[hidden email]>
writes:


> I think the benefits outweigh the disadvantages, so I'd like to see
> the external GPS connector gone.
>
> Any thoughts ?

As a user, I've used the external GPS connector about once, and it didnt
help much in that particular case(on a train). Making the device simpler
and leaner only improves it.

So my vote is to remove it.

>
> - Werner
--
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Re: gta02-core and external GPS antenna

Werner Almesberger
In reply to this post by H. Nikolaus Schaller
Dr. H. Nikolaus Schaller wrote:
> There are some requests for a 3.5 mm Headset connector...

Oh yes, that one is a really popular idea. Joachim, Joerg, and I
discussed this a lot for the gta02-core-like design some months
ago. Joachim gave the perfect use case: hardly anybody uses a
wired headset these days. But a lot of people use their phone as
an MP3 player they can bring to work. For an MP3 player, all you
need is the audio output, no microphone. And the universal
standard for audio output is the 3.5 mm jack.

So far, so good. But then we realized that 3.5 mm receptacles
are too big for the space available, even if you go all the way
to the battery connector. (The battery connector can't move
without a case redesign.)

There's also the issue that a 3.5 mm receptacle is taller, so
you don't only have to make a bigger hole in the case, but you
also have to change its center. Height vs. the inner "floor"
of the case is probably an issue as well.

So it's trickier than it seems. If someone can find a 3.5 mm
receptacle that actually fits in the GTA02 mechanical design in
all three dimensions, that would be an interesting discovery,
though.

- Werner

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Re: gta02-core and external GPS antenna

Yorick Moko
In reply to this post by joakim
As an end-user i have never used an external GPS antenna and don't plan to

On Thu, May 28, 2009 at 10:15 PM,  <[hidden email]> wrote:

> Werner Almesberger <[hidden email]>
> writes:
>
>
>> I think the benefits outweigh the disadvantages, so I'd like to see
>> the external GPS connector gone.
>>
>> Any thoughts ?
>
> As a user, I've used the external GPS connector about once, and it didnt
> help much in that particular case(on a train). Making the device simpler
> and leaner only improves it.
>
> So my vote is to remove it.
>
>>
>> - Werner
> --
> Joakim Verona
>
>
> _______________________________________________
> Gta03 mailing list
> [hidden email]
> https://lists.openmoko.org/mailman/listinfo/gta03
>

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Re: gta02-core and external GPS antenna

Korbinian Rosenegger
In reply to this post by Werner Almesberger
Hi

I just noticed that i replied directly to Werner instead to the list, so
i resend it. Maybe the Reply-To header should be set by the list?



On Thu, 2009-05-28 at 16:53 -0300, Werner Almesberger wrote:
> There's one simplification that looks attractive to make in gta02-core
> and that's to remove the external GPS antenna connector. From what I've
> heard, this antenna is rarely used in the FreeRunner, and for
> stationary use, one could connect an external antenna to the socket for
> the internal antenna.

I use the external GPS antenna in my car, and it gives me a quicker and
better first fix. About 35 sec/7 satellites with and 45 sec/4 satellites
without antenna, IIRC. I haven't tested whether there is a difference in
accuracy while driving with antenna, and I don't know if there's any
difference between my GTA02v5 and a fixed GTA02v6.

As an user I could live without the external connector.
I guess the PCB design changes in a way that there are not just some
parts missing, so guys with SMD solder skills can't just re-add the
external connector.


> - removing the connector leaves an empty hole in the case

What about using this empty hole for IrDA?
If the IR-LED has enough power it could also be used as a remote control
(i guess, never tried that).


cu Korbi



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Re: gta02-core and external GPS antenna

Davide
In reply to this post by Werner Almesberger
O Xoves, 28 de Maio de 2009, Werner Almesberger escribiu:


> I think the benefits outweigh the disadvantages, so I'd like to see
> the external GPS connector gone.
>
> Any thoughts ?


I'm using external GPS connector almost daily :).


I use FR a lot for generating GPS traces for OpenStreetMap.
For me it's a must, and I know at least one more person who uses FR for OSM like me.


>
> - Werner
>
> _______________________________________________
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> [hidden email]
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Clave pública PGP/GPG: http://davide.garabana.com/pgp.html


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Re: gta02-core and external GPS antenna

Christian Adams

Am 29.05.2009 um 00:22 schrieb David Garabana Barro:

O Xoves, 28 de Maio de 2009, Werner Almesberger escribiu:

> I think the benefits outweigh the disadvantages, so I'd like to see
> the external GPS connector gone.
>
> Any thoughts ?

I'm using external GPS connector almost daily :).

+1 for daily use .. please don't remove in future phones


I use FR a lot for generating GPS traces for OpenStreetMap.
For me it's a must, and I know at least one more person who uses FR for OSM like me.


Christian (Morlac) Adams
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L++(+++);E---;W++;N(+);o?;K?;!w;!O;!M+>;!V;PS(+);PE;
Y+;PGP++;t+(++);5(+)>++;X(+);R*;tv->+;b++(+++);DI++;
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Re: gta02-core and external GPS antenna

Davide
On Friday 29 May 2009 09:15:45 Christian Adams wrote:

> Am 29.05.2009 um 00:22 schrieb David Garabana Barro:
> > O Xoves, 28 de Maio de 2009, Werner Almesberger escribiu:
> > > I think the benefits outweigh the disadvantages, so I'd like to see
> > > the external GPS connector gone.
> > >
> > > Any thoughts ?
> >
> > I'm using external GPS connector almost daily :).
>
> +1 for daily use .. please don't remove in future phones

Another solution could be to allow access to internal connector only removing
back cover. Not so practical, but better than nothing.

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Re: gta02-core and external GPS antenna

Steve Mosher
In reply to this post by Werner Almesberger
Personally I always thought that a phone targeted at developers out to
have as
many ins and outs as practicable. That said, On the sales side we never
did see
much uptake for the external GPS antenna. From a logistics point of view
getting uniques off the board is a good good thing. I would concur with
the decision
to remove it. However, u may want to check with Tully on the mechanical
aspects.
I have his personal email here somewhere in case he doesnt answer the om
one.

Question: are you considering folding in the A8 changes? and the 1024 fix?
beware on the A8 microphone as it requires an annoying case mod. doable,
but annoying.

Steve

Werner Almesberger wrote:

> There's one simplification that looks attractive to make in gta02-core
> and that's to remove the external GPS antenna connector. From what I've
> heard, this antenna is rarely used in the FreeRunner, and for
> stationary use, one could connect an external antenna to the socket for
> the internal antenna.
>
> There are the following benefits in removing the external antenna:
>
> - reduced SMT cost by removing about a dozen components, some of them
>   unique. Due to its shape, The antenna connector may also need
>   special treatment in SMT, such as glueing.
>
> - fewer components means less risk of getting interferences. This goes
>   particularly for the external antenna socket when open.
>
> - simplifies the layout of the GPS RF circuit and thus reduces the
>   risk of us getting something wrong.
>
> - when investigating the SD/MMC vs. GPS problem, Andy found that the
>   antenna selection circuit is operating with an incorrect voltage.
>   Apparently, this didn't cause any observable problems, but then
>   you never know what's really behind the occasional glitch ...
>
> - in case future designs are made based on gta02-core, a smaller GPS
>   subsystem may allow for a smaller PCB size or give more room to
>   other subsystems
>
> There are also a few disadvantages:
>
> - if you really need the external GPS antenna along with the internal
>   one, this will not be a welcome change
>
> - the antenna connector also helps to hold the PCB in place. Without
>   it, there is only USB on that side of the board to assist the
>   snap-in mechanism. (Probably doesn't matter all that much, though.)
>
> - removing the connector leaves an empty hole in the case
>
> I think the benefits outweigh the disadvantages, so I'd like to see
> the external GPS connector gone.
>
> Any thoughts ?
>
> - Werner
>
> _______________________________________________
> Gta03 mailing list
> [hidden email]
> https://lists.openmoko.org/mailman/listinfo/gta03
>  


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Re: gta02-core and external GPS antenna

Esben Stien
In reply to this post by Werner Almesberger
Werner Almesberger <[hidden email]> writes:

> 3.5 mm receptacle

I'd say just remove the connector. If someone wants to use a wired
headset, they can use a USB headset.

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Re: gta02-core and external GPS antenna

cyrusdreams
In reply to this post by Davide
Am Freitag 29 Mai 2009 schrieb David Garabana Barro:

>  I use FR a lot for generating GPS traces for OpenStreetMap.
> For me it's a must, and I know at least one more person who uses FR for OSM
> like me.

And you really get better results with the external antenna? I do a lot of OSM
too. From my observation, the reception is the same unless you are in a car
and put the external antenna outside.

However, I had better reception during the time the GPS interfered with the
SD-Card, but that's long gone now.

I would vote to have the connector removed, as one can close the hole tightly
and have one less possibility for rain water to get into the phone (that is
my worst nightmare when using the GTA02 for OSM-mapping).

Greetings,
CyrusDreams

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Re: gta02-core and external GPS antenna

Werner Almesberger
In reply to this post by Davide
David Garabana Barro wrote:
> Another solution could be to allow access to internal connector only removing
> back cover. Not so practical, but better than nothing.

That's an interesting idea. The connector is currently exposed,
but you can only reach it if you remove the battery.

However, if it moved at the location of the external connector,
it would be possible to just drill a hole into the middle case
part that could be accessed by removing the bottom (or making
a hole there as well).

Perhaps even more useful, the MMCX connector could probably be
inserted such that is faces towards the center, so that one can
run the cable under the battery's edge and out of the device.

- Werner

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Re: gta02-core and external GPS antenna

Werner Almesberger
In reply to this post by Esben Stien
Esben Stien wrote:
> I'd say just remove the connector. If someone wants to use a wired
> headset, they can use a USB headset.

It's an interesting idea, but wouldn't they also want to use USB for
power ? Then you need a Y-cable, which makes things a bit complicated.

- Werner

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Re: gta02-core and external GPS antenna

Werner Almesberger
In reply to this post by Steve Mosher
Steve Mosher wrote:
> Question: are you considering folding in the A8 changes? and the 1024 fix?
> beware on the A8 microphone as it requires an annoying case mod. doable,
> but annoying.

I definitely want the audio changes, yes, even beyond GTA02v8.
I.e., amplifier removal. I hope Joerg will have a look when we
get to the audio design and see if we missed anything.

The new EMI-hardened microphone sounds good, but I wonder if we
actually need it, if the existing buzz fix already solves all
issues without introducing new ones. Component availability may
also be an issue, perhaps even the deciding factor.

The #1024 fix would be easy to implement. Instead of adding
another ceramic capacitor, we could just use a sufficiently
large low-ESR tantalum cap, so the layout wouldn't even have to
change.

The main problem with GSM at the moment is how we get the
design. The entire GSM side is non-public, schematics and
layout. I don't think Openmoko would have much of an issue with
releasing all this, but these things are under NDA with TI, so
TI would have to agree as well. We can knock on TI's door, but
I'm a little afraid they would have to recall people from
retirement to even know what that Calyoso thing is we're
talking about.

I'm also not sure if those NDAs are with Openmoko directly or
via FIC. Wolfgang probably knows.

An alternative would be if gta02-core could somehow license the
design from Openmoko and drop it in in a non-public way. Since
this would be the last gleaming of the whole Calypso complex
anyway, I wouldn't worry too much about the freedom aspects per
se. However, this would complicate handling the layout files on
the gta02-core side.

External GPS antenna connector removal seems to do more good
than harm. By simplifying the circuit and maybe cleaning up
some of the signals (I find the lack of filters on TX/RX a bit
irritating), we may very well recover a dB or two, making the
internal antenna almost as good as the external one.

- Werner

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Re: gta02-core and external GPS antenna

Steve Mosher
Werner Almesberger wrote:

> Steve Mosher wrote:
>  
>> Question: are you considering folding in the A8 changes? and the 1024 fix?
>> beware on the A8 microphone as it requires an annoying case mod. doable,
>> but annoying.
>>    
>
> I definitely want the audio changes, yes, even beyond GTA02v8.
> I.e., amplifier removal. I hope Joerg will have a look when we
> get to the audio design and see if we missed anything.
>
> The new EMI-hardened microphone sounds good, but I wonder if we
> actually need it, if the existing buzz fix already solves all
> issues without introducing new ones. Component availability may
> also be an issue, perhaps even the deciding factor.
>  
   Agreed.  does your design include the beads to prevent the RF from
getting into the mixer?
   I believe this is one of the differences between A7 and A8. A7 ( i
was told) is a bandaid on the
  output after the mixer, A8 ( i understood) fixed the root cause and
had ferrite beads added.
  Joerg will know. Preventing the RF from getting into the mixer is much
better ( wired mic for
  example is believed to cause buzz even in an A7?? )  If you haven't
heard an A8 it was,
for me, quite a pronounced improvement. Overall the S/N was perceptably
better. Andy
 may be a better source of information than I am. That said, the
improved mic would require
 that annoying little case mod.. not to bad for a DIY, but in mass pro
it would not be a good
thing.

> The #1024 fix would be easy to implement. Instead of adding
> another ceramic capacitor, we could just use a sufficiently
> large low-ESR tantalum cap, so the layout wouldn't even have to
> change.
>
> The main problem with GSM at the moment is how we get the
> design. The entire GSM side is non-public, schematics and
> layout. I don't think Openmoko would have much of an issue with
> releasing all this, but these things are under NDA with TI, so
> TI would have to agree as well. We can knock on TI's door, but
> I'm a little afraid they would have to recall people from
> retirement to even know what that Calyoso thing is we're
> talking about.
>
> I'm also not sure if those NDAs are with Openmoko directly or
> via FIC. Wolfgang probably knows.
>  
  Ya check with Wolfy.
> An alternative would be if gta02-core could somehow license the
> design from Openmoko and drop it in in a non-public way. Since
> this would be the last gleaming of the whole Calypso complex
> anyway, I wouldn't worry too much about the freedom aspects per
> se. However, this would complicate handling the layout files on
> the gta02-core side.
>  
 I'm looking at those issues.  It's probably best if you create some
kind of legal
 entity. Postmoko.
> External GPS antenna connector removal seems to do more good
> than harm. By simplifying the circuit and maybe cleaning up
> some of the signals (I find the lack of filters on TX/RX a bit
> irritating), we may very well recover a dB or two, making the
> internal antenna almost as good as the external one.
>  
 Ya,  I never saw any substatiated numbers on the gain from the external
antenna.
  there are of course reports of improved performance. It would be
interesting
  to see what you get by simplifying the circuit.
> - Werner
>  


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