FCDEV3B project status

[Mychaela Falconia]

Hi DS,

> Two very minor issues I ran into while compiling:
> - on Ubuntu and I presume Debian, /bin/sh links to dash instead of
> bash. The configure scripts expects bash, this is trivial to fix.

Where do the scripts expect bash?  Please tell me the specifics and
I'll fix it, as I never intended to depend on bash.

> - mokosrec2bin has to be in PATH. I found it in freecalypso-reveng
> and compiled it into /opt/freecalypso/bin

See doc/Compiling in the fc-magnetite source, lines 30-32.

> Now regarding the issue of the VCXO calibration, this is slightly less
> easy than I thought since the signal emitted by the DUT is not a pure
> signal but GSM bursts. I'll have a look into GNU Radio which has blocks
> for GSM provided by gr-gsm.

When calibration is done the "official" way, i.e., with a CMU200, the
CMU is indeed used in the GSM-specific mode (the GSM-specific, MS-
specific, per-band software options must be installed on the CMU200),
rather than the generic RF analyzer mode, for both VCXO and Tx power
level calibration steps (i.e., for both frequency offset and power
measurements), as indeed the DUT transmits GSM bursts in both cases -
the only thing that GSM MS hardware can transmit!

I've said it many times before, but I'll reiterate: I do not expect
FreeCalypso users or even hard-core FC firmware developers to do their
own RF calibration, as it is really a *factory* job to be done by
*hardware manufacturers*.  But if you would like to do your own
calibration with GNU Radio instead of a CMU200 just for fun, go for
it! :-)

I got the VCXO calibration under control back in April, so the board
that went to DS had its VCXO already calibrated before it left my lab.
Rx "magic gain" calibration was quite easy once I got the Aux Tx
generator working on my CMU200 as a substitute for the non-working
main RF gen, and it is non-critical anyway as the difference between
compiled-in GMagic numbers and properly calibrated ones is tiny.

All that is left to be done now is the calibration of Tx power levels.
My current stumbling block in that direction is that the highest Tx
power levels I can get out of the FCDEV3B no matter how high I crank
up the APC DAC are still below the maximum spec-defined power levels.
Here is what I am currently getting in the 900 MHz band:

APC DAC=70: 0.82 dBm
APC DAC=100: 8.83 dBm
APC DAC=150: 15.08 dBm
APC DAC=200: 18.69 dBm
APC DAC=300: 23.38 dBm
APC DAC=400: 26.35 dBm
APC DAC=500: 28.49 dBm
APC DAC=600: 30.20 dBm
APC DAC=700: 30.76 dBm
APC DAC=800: 30.91 dBm
APC DAC=900: 31.11 dBm

In the 1800 MHz band:

APC DAC=70: -1.70 dBm
APC DAC=100: 5.28 dBm
APC DAC=150: 11.07 dBm
APC DAC=200: 14.88 dBm
APC DAC=300: 19.85 dBm
APC DAC=400: 23.21 dBm
APC DAC=500: 25.62 dBm
APC DAC=600: 27.63 dBm
APC DAC=700: 28.77 dBm
APC DAC=800: 28.96 dBm
APC DAC=900: 29.09 dBm

In the 1900 MHz band:

APC DAC=70: -2.38 dBm
APC DAC=100: 4.71 dBm
APC DAC=150: 10.74 dBm
APC DAC=200: 14.48 dBm
APC DAC=300: 19.08 dBm
APC DAC=400: 22.04 dBm
APC DAC=500: 24.27 dBm
APC DAC=600: 26.00 dBm
APC DAC=700: 27.31 dBm
APC DAC=800: 27.54 dBm
APC DAC=900: 27.62 dBm

Per the spec, our MS is supposed to put out 33 dBm at the highest power
level in the EGSM band and 30 dBm in the DCS and PCS bands, but as you
can see in the measurement results above, we are not able to get that
high.  My planned next steps in this investigation are as follows:

1. See if the VBAT power supply voltage fed to the FCDEV3B makes a
   difference.  Right now I am using one of our super-convenient
   compact power supplies (the same kind as I sent to DS), and it puts
   out about 3.7 V.  I also have a lab bench power supply on which I
   can tune the voltage with a knob (for example, see what happens at
   4.2 V, corresponding to a fully charged battery), but I sent that
   power cable to Serg back in April, so I need to make another one.

2. Connect my CMU200 to the RF test port on an Openmoko-made and Om-
   calibrated GTA02 and see what power levels our "golden reference"
   hw puts out.  I already ordered the necessary RF connection adapter
   when I got paid on Friday, and now I am waiting for it to arrive.

M~