VCXO calibration

[Serg l]

This is a huge success! I'm looking forward to dig in.

On Apr 14, 2017 4:16 AM, "Mychaela Falconia" <mychaela.falconia at gmail.com>
wrote:

> Hello FC community,
>
> I got to perform a manual VCXO calibration procedure (using the CMU200)
> on one of my FCDEV3B boards based on my reconstructed understanding,
> and it seems to be working: the numbers I got out of my manual cal are
> in the same range as those read out of Openmoko-made GTA02 units
> (which is expected, as we are using exactly the same VCXO circuit
> including the crystal part), and after doing this VCXO calibration I
> was able to connect to the local GSM network and make some calls.
> (The latter success should not be considered a definite proof of
> perfect calibration, though - it once succeeded for me last weekend
> before this cal when the temperature in the room was colder.)
>
> I just wrote a document describing what I did, so when Serg gets his
> board tomorrow, he will have at least a chance of being able to
> reproduce it.  The write-up is in doc/VCXO_calibration in the
> freecalypso-tools Hg repository - enjoy!
>
> My next step is going to be trying to operate the CMU200 programmatically
> through its SCPI-based command interface, so I can start automating
> these calibration procedures - we need automation for repeatability,
> and we are also going to need Rx and Tx calibration (beyond the VCXO)
> which would be too impractical to perform manually - too many
> repetitive steps.
>
> M~
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