FreeCalypso New Year and US-band FreeRunners

Mychaela Falconia mychaela.falconia at gmail.com
Wed Dec 27 22:52:20 UTC 2017


Hello FreeCalypso community,

Happy New Year to all of you!  I am back from doing nurse duty (one of
my family members had surgery before Xmas and I was her nurse for a
few days - she is doing great) and looking forward to making a lot
more FreeCalypso progress in 2018.  I have successfully reverse-
engineered Pirelli's changes to TI's old PWR Li-ion battery charging
code, figured out how they do the constant voltage control loop to
compensate for imperfections in the Iota ABB hardware, and expect to
have battery charging working on both the Pirelli and the C139 once I
implement the same logic in our own FCHG code.  I am working on a
Magnetite hybrid configuration that has CSD, fax and GPRS support
disabled - I still need to debug it, but if we can get it working, it
will be helpful for the C1xx targets on which these data services
cannot be made use of anyway.  And when the working world fully
reopens after New Year, I will continue the pursuit of the sleep mode
bug on our own FCDEV3B hardware.

With the holiday greetings out of the way, I have a solicitation: is
there anyone in our community who owns an Openmoko device of the
850/1800/1900 MHz version, aka the so-called "USA bands" version?  I
have several units (4 complete ones plus 2 bare boards) of the
"European" version (900/1800/1900 MHz), but I have never even seen a
"US bands" FreeRunner in person.

If anyone in our community does own a FreeRunner of the "US bands"
version, you can help our mission of producing new Calypso phone and
modem hardware by doing one of the following:

Option 1: disassemble the device, extract the motherboard, remove the
WLAN daughterboard from it, then remove the metal shield cover over
the GSM section, then look at it under a good microscope and tell us
the markings imprinted on the magic SAW filter part that differentiates
between 850 MHz and 900 MHz versions.

Option 2: send the device to me with the understanding that I will
subject it to the just-described disassembly procedures, then put it
back together and send it back to you completely unharmed.  As an
additional incentive, if the FreeRunner in question suffers from the
infamous bug #1024 defect and has not yet received the hardware rework
that fixes it (a capacitor change), I can apply that fix before
sending the device back to you.  Making the capacitor change that
fixes bug #1024 requires exactly the same disassembly that is needed
to access the SAW filters, hence if I am going to disassemble a FR to
see what SAW filters it has, I can easily apply the #1024 fix at the
same time.  (And no, I won't be doing the soldering myself, instead I
will have it done professionally at Technotronix, the same shop where
our own FCDEV3B modem boards have been built.)

OM made their GTA02 devices in two versions, the so-called "EU"
version and the so-called "US" version, or as I prefer to call them,
tri900 and tri850, as they are called in the FreeCalypso RF
calibration tool suite.  The only diff between the two is one SAW
filter: a different part is populated onto the same PCB footprint,
either one whose passband matches the EGSM downlink band (tri900
version), or one whose passband matches the GSM850 DL band (tri850
version).  We know the part number for the EGSM DL band SAW filter: it
is Epcos B7820; this part number is imprinted on the physical part in
OM-made tri900 FR units, and we've successfully used the same part on
our own FCDEV3B modem boards.  But we currently don't know the part
number for the other filter version that needs to be used to build
tri850 devices, and the lack of this part number knowledge is
currently preventing us from being able to build such devices and thus
from being able to operate in the GSM850 band, which is apparently
still used in some parts of Latin America, from what I hear.

If someone would be willing to lend me a "US bands" FreeRunner with
the understanding that I will need to take it thoroughly apart and
then put it back together, or could do the disassembly and microscope
examination procedures themselves and post the results, we would learn
that currently-missing magic part number, and gain the following
abilities:

1: the ability to make our FCDEV3B boards in both tri900 and tri850
   versions, and

2: the ability to convert Openmoko-made units from one band config to
   the other in either direction, with the same amount of surgery on
   the device as needed for the bug #1024 rework, followed by
   recalibration on the CMU200.

So, do we have anyone here who owns one of those apparently-super-rare
"US bands" FreeRunners and would be willing to help?

Hasta la Victoria, Siempre,
Mychaela aka The Mother


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