Custom calypso board

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Harald Welte laforge at
Sun Jul 15 21:51:22 UTC 2012

Hi again,

there have been some comments and feedback to my original posting,
but I was actually naively hoping for a bit more input.

Particularly the "modifications" parts lile:

>  * external clock input / buffered clock output

Any ideas how this should be implemented?  Adding the buffered output is
relatively simple, and it can always be present whether it is used or

More interesting is the clock source, where I would like to see a
switchable clock source between:
 * regular inetrnal VCTCXO
 * external clock input (U.FL)

The external input could be sourced from one of our OCXO boards for
higher stability.  Or you can of course source the clock input of one
board using the buffered output of another.

Does anyone have a good idea how to implement the actual switch?  I
think it would be best to have it software-switchable from a GPIO...

>  * RF connector standard u.fl or SMA or optionally separate Rx/Tx?

Here also we have the question of how to choose between the options.

If nobody comes up with a better idea, I would probably simply have a
placement option along the lines of a capacitor that can be soldered
either in the direction of the antenna switch (for duplex) or into the
direction of separate u.fl sockets for rx and tx.  In fact,t we can e.g.
route Rx always via the switch and do that procedure only for Tx.

>  * additional / unused TPU ports

One of my ideas here was to be able to issue a TPU event from one board
and use it to trigger something on another board.  The question is how
exactly the second half would be implemented.  We could connect it to an
interrupt input (like sim card detect which even is a FIQ on the ARM).
But would that really help?  Unfortunately the TPU has no triggers for
external events (which would be 100% synchronous).

If you have inputs to any of these topics, or have some other ideas of
what could or should be done, feel free to discuss them here!

- Harald Welte <laforge at> 
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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