FC Venus progress update

[Mychaela Falconia]

Hello FreeCalypso community,

This post is a periodic update on what I am doing in the project.
Right now I am still working on designing our next development board
FC Venus, the one that will serve as a successor to FC Luna for
handset fw development purposes.  Right now the schematic-level design
of this board is tentatively complete:

https://www.freecalypso.org/hg/freecalypso-schem2/

Tentatively complete means that I don't expect to make any further
changes to this schematic-level design unless necessitated by part
availability difficulties.  I have already secured most of the parts
needed for this board, and there are currently only a few parts left
that are included in the design but which I haven't physically secured
yet - if some of these parts turn out to be too difficult to procure,
I may need to change the design to use alternative parts that are more
readily available, but otherwise it is complete.

The current situation with part availability is a nightmare!  I am NOT
talking about our "special" Calypso parts that have been out of
production for almost two decades now and are available only from grey
market surplus - those I have secured many years ago in conjunction
with FCDEV3B project and earlier, and they are still good for FC Venus.
Instead many of our "regular" parts, the ones which anyone could order
from Digi-Key at any time in any desired quantity, are now out of stock
and available only with insanely long lead times, as in many months to
a whole year.  In order to secure all of the critical parts that will
be needed for the first batch of Venus boards without waiting into the
second half of 2022, I had to jump around with alternative sourcing (I
strongly prefer Digi-Key, but this time I had to turn to Mouser and
Newark for some of the parts), and in some cases switch to different
parts which I could grab.

FC Venus board can be viewed as consisting of the following major
subdivisions:

* The Calypso core will be similar to what we built on FCDEV3B, except
for a change from triband to quadband, using knowledge gained from
reverse eng of iWOW TR-800 modules.

* There will be a whole bunch of peripherals: LCD, keypad, magnetic
buzzer, 3 different audio channels, battery charging circuit.  Some of
these peripherals are out of the critical path: if they don't work, or
if we have to omit them because parts are missing, the rest of the
board will still be useful and valuable to the project.

* There will be a built-in FT2232D subsystem for host computer
interface to the pair of Calypso UARTs, similar to a built-in DUART28,
but slightly simplified given the fixed use case.  If this subsystem
doesn't work or needs to be omitted because of part shortage, all
critical signals are also wired to a 10-pin header to which an external
DUART28 adapter can be connected, saving the day.

FT2232D chips were particularly hard to get.  Right now the official
lead time estimate is 2023-01 (yikes), and there are various people on
ebay and other marketplaces who sell these chips for as much as $150
each!  So how did I get them then?  Answer: I called the USA office of
FTDI, exchanged emails with their sales team as directed, and they
found 100 pcs which they could sell me for a price that was only mildly
inflated.  (I paid $966.38 after shipping for these 100 pcs of FT2232D,
whereas the regular price in a world without shortages is $7.14 apiece
for single pieces or $5.32 apiece for qty 100 - so not too terribly
inflated, especially compared to what ebay etc sellers are asking.)

The complete FT2232D subsystem consists of additional parts beyond the
FT2232D chip itself, and right now I have all of those parts secured
except the 6.00 MHz crystal.  There are plenty of crystals in this
frequency in large packages, but my design calls for a low-profile (no
more than 1.5 mm height) SMT package, so it can fit inside what I
intend to be a shieldcan section.  If I am not able to obtain the
necessary slim-package crystals in time for the first build of Venus
boards, then those boards will have the entire FT2232D subsystem
omitted, and I will bring them up using an external DUART28 adapter.
Other parts whose in-time availability is currently uncertain reside
in the peripheral circuits for the buzzer, the loudspeaker and battery
charging.

Beyond part sourcing issues, the design of FC Venus is complete at the
schematic-equivalent level, but PCB layout hasn't been started yet.  I
plan to work with the same PCB layout contractor who did our DUART28
and Caramel2 boards last year, but before I can hand the design off to
him, I need to create footprints in pcb-rnd format (using new pcb-rnd
data model features and conventions) for all components on this board.
These pcb-rnd footprints are the next big task I need to work on to
bring FC Venus project forward.

The LCD module on FC Venus will be Formike KWH020ST23-F01, and the
backlight circuit will be MAX1916-based.  This LCD module and this
backlight circuit have already been proven good on our lunalcd2 board
in August of this year.  Last month I finally got our custom-made
metal bracket parts for securing our LCD module more solidly on "bare"
development boards without a phone case, and I got a new lunalcd3
iteration on which this metal bracket will get tested.  lunalcd3 PCBs
are now on their way to me from China, and I will probably get them
assembled shortly after New Year.

Finally, there is one critical accessory for FC Venus that is currently
being custom-made for us in China: our FC-HDS4 wired headset, discussed
here earlier.  Earlier this week I sent the payment to the headset
manufacturer with the go-ahead to produce 100 pcs of FC-HDS4, and they
are now making these headsets.  This FC-HDS4 will be a required
accessory for FC Venus: the main Iota audio channel (EAR/MIC) will be
wired to a 2.5 mm TRRS jack in iWOW's pinout (same as on Caramel2),
and the headset will need to be plugged into that jack in order to
exercise voice calls and to hear the UI firmware's beeps and whatnot.

So that's the current status of FC Venus.  Once we get these boards
built, assuming that we have good yield and no major design errors,
they will be made available to everyone who would be interested in a
board for its intended purpose of running FreeCalypso firmware.
However, I will NOT support or provide hardware to anyone who would
seek to misuse it for the purpose of running OBB crapware.

Hasta la Victoria, Siempre,
Mychaela aka The Mother