Good news: also WLAN in bits

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Good news: also WLAN in bits

Werner Almesberger
Just got some good news from Sean: the WLAN daughterboards aren't
assembled yet. This means that we have more flexibility for placing
the components. With a little luck, there may even be space on the
side of the GSM module.

Now, the downside is that we need a few more symbols (the level
shifter, the WLAN module, and some smaller pieces). Any takers ?

- Werner

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Re: Good news: also WLAN in bits

AlvieBoy
Werner Almesberger wrote:
> Just got some good news from Sean: the WLAN daughterboards aren't
> assembled yet. This means that we have more flexibility for placing
> the components. With a little luck, there may even be space on the
> side of the GSM module.
>
> Now, the downside is that we need a few more symbols (the level
> shifter, the WLAN module, and some smaller pieces). Any takers ?

I can handle that today. I'll post news when I'm finished.

Álvaro

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Re: Good news: also WLAN in bits

AlvieBoy
Álvaro Lopes wrote:
>> Now, the downside is that we need a few more symbols (the level
>> shifter, the WLAN module, and some smaller pieces). Any takers ?
>
> I can handle that today. I'll post news when I'm finished.

OK, I must confess I was expecting something simpler :)

The level shifter (adg3304) is done and commited, please review.

Regarding the other components:

 * U7801 (WLAN module) - I could not find a proper datasheet for it [1]. We can derive information from openmoko schematics, but I'd really like to crosscheck
this with a real datasheet.

 * U7802 (Bandpass filter) - Our filter is not listed on their site [2], and datasheet access requires some access code.

 * CON7801 - Do we have this connector already [4] ?

 * ANT7801 - There was some previous discussion about this one [3], I am not sure if the symbol is ready.

 * Drilling and Shielding pads. Any ideas on these ?

Álvaro

[1] http://wiki.openmoko.org/wiki/Accton_WM3236AQ
[2] http://www.acxc.com.tw/product/bf2520/bf2520.htm
[3] http://lists.openmoko.org/nabble.html#nabble-td3039217
[4] http://www.murata.com/catalog/o30e8.pdf

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Re: Good news: also WLAN in bits

Werner Almesberger
?lvaro Lopes wrote:
> The level shifter (adg3304) is done and commited, please review.

Thanks ! I've added it to the expanded view and reviewed it.
Flawless !

>  * U7801 (WLAN module) - I could not find a proper datasheet for it [1].

Me neither :-(

> We can derive information from openmoko schematics, but I'd really like
> to crosscheck this with a real datasheet.

I can compare it against the "internal" data sheet.

>  * U7802 (Bandpass filter) - Our filter is not listed on their site [2],
> and datasheet access requires some access code.

I think it's this one:
http://www.anttechcorp.com/images/acx_bf_PDF/BF2520-B2R4CAB.pdf

>  * CON7801 - Do we have this connector already [4] ?

Hmm no, the one we have (CON7601) has different connections.

>  * ANT7801 - There was some previous discussion about this one [3],
> I am not sure if the symbol is ready.

The antenna is the same as for BT, but the symbol we have there doesn't
look right. I've pried one from an old BT module:

http://people.openmoko.org/werner/ant/ant-bot.jpg
http://people.openmoko.org/werner/ant/ant-top.jpg

>  * Drilling and Shielding pads. Any ideas on these ?

I'd say we go for "pretend shielding": leave enough room for a
hypothetical shield to be added, but don't actually try to make one.

Of course, if someone has time and tools for making a real shield,
contributions are always welcome :-)

- Werner

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Re: Good news: also WLAN in bits

AlvieBoy
Werner Almesberger wrote:
> ?lvaro Lopes wrote:
>>  * U7801 (WLAN module) - I could not find a proper datasheet for it [1].
>
> Me neither :-(

I did the best I could. Please review.

>>  * U7802 (Bandpass filter) - Our filter is not listed on their site [2],
>> and datasheet access requires some access code.
>
> I think it's this one:
> http://www.anttechcorp.com/images/acx_bf_PDF/BF2520-B2R4CAB.pdf

Added. Review as usual. I left IN/OUT pins as passive.

Álvaro

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Re: Good news: also WLAN in bits

Rene Harder
In reply to this post by Werner Almesberger
Werner Almesberger wrote:
>
>>  * ANT7801 - There was some previous discussion about this one [3],
>> I am not sure if the symbol is ready.
>>    
>
> The antenna is the same as for BT, but the symbol we have there doesn't
> look right. I've pried one from an old BT module:
>
>  

In your pictures most of those pins look NC. Shall we add them to the
symbol and just do not connect them? I guess they only exist to be able
to properly mount the antenna to the PCB.
On the other hand If we have to redesign the WLAN module why don't we
use an embedded 2.4GHz antenna instead of this one so we can save some
volume. Here [1] you can find a neat design from TI which has an area of
approx 15 x 6mm.

[1] http://focus.ti.com/lit/an/swra117d/swra117d.pdf

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Re: Good news: also WLAN in bits

Werner Almesberger
In reply to this post by AlvieBoy
?lvaro Lopes wrote:
> I did the best I could. Please review.

- NC pins should better be "Unspec" (or omitted), not Passive

- the data sheet has CLK_REQ as an output, but I think you're right :-)

- RESET is active-low, so we should call it nRESET

- pin 35 should be NC, not RST_OUT_L. (That's a bug in the Openmoko
  schematics. The 48QFN package has no reset output. There is a
  81QFN - no kidding, an odd number of pins in a quad package - that
  does.)

> Added. Review as usual. I left IN/OUT pins as passive.

Perfect. Thanks a lot !

I've added them to the expanded bt.sch and removed the connector.
I think we'll need a separate WLAN sheet in the main schematics,
to keep things from getting too crowded.

- Werner

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Re: Good news: also WLAN in bits

Werner Almesberger
In reply to this post by AlvieBoy
By the way, here's an inside view of the WLAN daughterboard, after
removal of the can:

http://people.openmoko.org/werner/wlan-inside/

As one can see, it's indeed the 48QFN version that we have.

- Werner

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Re: Good news: also WLAN in bits

Werner Almesberger
In reply to this post by Rene Harder
Rene Harder wrote:
> [1] http://focus.ti.com/lit/an/swra117d/swra117d.pdf

That's a nice little antenna ! But does it really save space ?
E.g., does it occupy both sides of the board or can we put stuff
on one side without crippling the performance of the antenna ?

Also, while the antenna is flat, what could we put into the
airspace above it that doesn't disturb it or is disturbed by
it ?

- Werner

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Re: Good news: also WLAN in bits

AlvieBoy
In reply to this post by Werner Almesberger
Werner Almesberger wrote:
> ?lvaro Lopes wrote:
>> I did the best I could. Please review.
>
> - NC pins should better be "Unspec" (or omitted), not Passive

Done

> - the data sheet has CLK_REQ as an output, but I think you're right :-)

There's no point on having and output with a 10k resistor to ground, I think :)

> - RESET is active-low, so we should call it nRESET

Done.

> - pin 35 should be NC, not RST_OUT_L. (That's a bug in the Openmoko
>   schematics. The 48QFN package has no reset output. There is a
>   81QFN - no kidding, an odd number of pins in a quad package - that
>   does.)

Done.


Álvaro

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