Work toward FreeCalypso handset

[Das Signal]

Hi Mychaela,

First of all, congratulation on your successful operation and recovery,
I am glad everything went fine :-)

Although I'm afraid I don't have much news to share with the community,
I am nonetheless thankful for your continued work towards a completely
free handset, for which FC Venus is (imho) an important stepping stone.

In addition to the exellent FCDEV3B & Caramel2 (and the quite rare iWOW
DSK), a true Pirelli-like handset will be super nice; for instance having
a real loudspeaker is a very important requirement, and something lacking
on the Motorola C1XX. Similarly, the DP-L10 could use a larger LCD screen,
and the Wi-Fi/camera could be dropped completely. Also, the addition of a
real lithium battery to FC Venus is super cool and a great feature :-)

--DS

On Tue, Sep 28, 2021 at 06:18:05PM -0800, Mychaela Falconia wrote:
> Hello FreeCalypso community,
> 
> I am still slowly trudging toward my dream goal of designing and
> building my own FC Libre Dumbphone that would serve as a source-enabled
> replacement for the Calypso-based but sans-source Pirelli DP-L10.  The
> purpose of this post is to share some updates on current developments
> toward this goal.
> 
> The biggest update at the moment is that I have finalized the selection
> of LCD module that will be used in our Pirelli-replacing FC handset,
> and I have bought 100 pcs of this chosen LCD module, a quantity which
> I expect to be a lifetime buy, covering all anticipated prototyping
> iterations.  The LCD module I settled on is a 176x220 pixel 2.0" TFT
> made by LCD manufacturer Formike; here is the datasheet:
> 
> ftp://ftp.freecalypso.org/pub/embedded/LCDs/KWH020ST23-F01.pdf
> 
> In terms of the physical size of the display active area in mm, our
> 2.0" diagonal LCD is about 72% bigger than Pirelli's 1.5" diagonal:
> the AA of our new LCD is well-defined to be 31.68x39.60 mm; for
> Pirelli's LCD we have no specs, but measuring the lit-up AA with a
> ruler shows about 26x28 mm.  But in terms of information display
> capacity, our new 176x220 pixel LCD is 2.36 times larger than
> Pirelli's 128x128 pix!  In any case, my choice of 176x220 as the pixel
> size for our phone LCD comes from my desire to reuse as much as
> possible from TI's D-Sample demo/prototype/PoC UI which is coded for
> this LCD pixel size, and the physical size of 2.0" diagonal comes from
> the industry standard size selection: most 176x220 pixel LCDs including
> the one I ultimately ended up choosing are made in this physical size,
> not some other.
> 
> I also took a few pictures, although my skills with the camera are
> abysmal - I am an engineer, not a photographer:
> 
> https://www.freecalypso.org/members/falcon/pictures/Formike_LCD/
> 
> In these pictures you can see the front and back of a bare LCD module,
> and our lunalcd2 test board which I made a couple of months ago.  This
> test board has the LCD module mounted on it (key mounting feature: see
> how the module's FPC tail is folded under the body of the module in
> our mounting arrangement), and the LCD is connected to our Luna
> interface from 2020.
> 
> The strip of Kapton tape seen in the lunalcd2.jpeg photo is a hack for
> holding our LCD module in place.  In a complete phone handset with
> plastics, there will be no issue: in the classic mechanical design of
> all standard phones, there are screws that hold together the front and
> back plastic pieces, and the resulting tight grip structure constrains
> the LCD module to staying where it needs to be.  However, in a bare
> development board setup without plastics, we get this unexpected
> annoyance: there is a certain elastic force (originating in the area
> where the tail is folded under the module) that pushes the bottom of
> the LCD module up, away from the PCB, this force acts against gravity
> and against the adhesive, but it is strong enough to lift the bottom
> of the LCD module in a way that at least to me looks aesthetically
> displeasing and feels like a significantly weakened system.  On
> lunalcd2 I am using a strip of Kapton tape wrapped around the board to
> keep the LCD module from lifting up at the bottom end (the undesirable
> elastic force is countered by the tension of this tape), but as my
> next iterative solution, I am commissioning a local sheet metal shop
> to make us a custom metal bracket that will be more robust than the
> tape.
> 
> Right now I am waiting for this hired local sheet metal company to
> finish the design and fabrication of our LCD retaining bracket, and I
> am also waiting for this back-ordered part from Digi-Key:
> 
> https://www.digikey.com/en/products/detail/cui-devices/DS04-254-1-04BK-SMT/11310949
> 
> This part has been on backorder since July 1; originally it was
> supposed to arrive around the time of my surgery in late August, but
> now it says October 11.  The purpose of this DIP switch is to select
> the backlight LED current from 1 to 15 mA in 1 mA increments, allowing
> us to evaluate the readability of the LCD under different ambient
> lighting conditions with different backlight LED currents, with the
> goal of selecting a subset of just 4 possible LED currents for our
> Venus board.  Because of this insanely long backorder issue, I got our
> current lunalcd2 board (the one pictured) assembled back in August
> using a substitute part, a DIP switch pack with less convenient flush
> actuators instead of raised ones.  But now that we are getting a
> special retaining metal bracket made, I plan on producing a lunalcd3
> test board (like lunalcd2, but with appropriate mounting holes added
> for the bracket) before proceeding with FC Venus, and given that
> Digi-Key's promised delivery date of Oct 11 is approaching, I am
> hoping to use the better DIP switch part on lunalcd3.
> 
> At this point you have every right to ask: so what is the big deal,
> why am I fussing so much over the LCD and its mounting?  The answer is
> that I am planning our next FreeCalypso development board, and this
> next FC Venus board will be a major advancement toward our FC Libre
> Dumbphone handset goal: it will be just like a complete phone, but in
> the physical form factor of a bare board, without any plastics or
> mechanical design.  With our current FC development boards so far,
> that is FCDEV3B and Caramel2, you need to connect the board to a host
> computer and control it with AT commands in order to make it do
> anything interesting, as in connecting to GSM networks, making and
> receiving calls, sending and receiving SMS.  But FC Venus will be on
> the next level: the board will include the just-described LCD and
> keypad buttons in addition to the Calypso GSM core, and it will be
> designed to be powered either by a fixed supply like our current
> boards or by a real Li-ion battery, with charging of that battery
> managed by the Calypso chipset and our firmware!  My vision is that I
> will be able to mount this Venus board plus its powering 18650 battery
> on some sturdy substrate such as a thick sheet of acrylic, and take it
> out with me on social outings, demonstrating it to people outside my
> cave - and given that I live right next to USA-Mexico border and given
> my ability to cross this border freely back and forth without being
> subject to any Covidian cult rituals, I hope to be able to demo this
> next stage of FreeCalypso in both countries.
> 
> Right now we have only one FC hardware platform on which we can run
> firmware that is controlled with an LCD+buttons UI, rather than via AT
> commands, and this platform is FC Luna.  However, this Luna platform
> is very unwieldy - it is not a single board, but a set of 4 boards
> interconnected with ribbon cables: a Caramel2 motherboard, a lunalcdX
> board, a keypad board and a DUART28 adapter for the host computer
> interface.  Here is a fairly recent photo of the whole mess:
> 
> https://www.freecalypso.org/members/falcon/Caramel2/luna-setup-20201206.jpeg
> 
> As you can surely tell from the above photo, this Luna setup is not
> exactly suitable for field demos to audiences with limited attention
> spans where first impression is everything, even if I went through the
> process of mounting all of these pieces on some solid substrate like
> our dear Das Signal did.  Thus the logical next step is clear: we need
> to eliminate the maze of ribbon cables and integrate everything on one
> board.  Furthermore, instead of using a Tango module for the Calypso
> core like we did on Caramel2/Luna, our Venus board will be made from
> "raw" Calypso and accessory chips like FCDEV3B - this approach will
> make both design and fabrication more expensive, but it will give us
> access to a few additional chipset signals which iWOW didn't bring out
> on their TR-800 module.  By connecting a magnetic buzzer to Calypso
> BU/PWT output like on TI's D-Sample board, we will produce a platform
> for making a smooth transition from buzzer ringing to Melody E1, and
> by connecting to all 3 Iota audio channels, we will prototype the
> complete audio routing subsystem for the Pirelli-replacing handset.
> 
> If you would like to read more about this Venus board plan and about
> the more distant handset for which it will serve as a prototype, here
> is the detailed design specification:
> 
> https://www.freecalypso.org/hg/freecalypso-docs/file/tip/FC-handset-spec
> 
> There is just one more complication which I am currently working on:
> we need to get a custom wired headset made for us.  Trying to use any
> of the commonly available already existing headsets won't work:
> 
> * Today's mainstream consumer 3.5 mm headsets for Apple/Android phones
> won't work because they are stereo (left and right ear), whereas we
> need monaural, as in only one earbud.
> 
> * Openmoko headsets won't work for the same reason: while they are
> infinitely better morally and philosophically than sheeple ones, they
> are still stereo.
> 
> * Old historical headsets made for classic historical dumbphones (both
> Motorola C1xx and non-Calypso classic phones like Nokia) are still
> available in substantial quantities on certain markets, but they all
> feature the typical 3-wire TRS arrangement with the earpiece speaker
> connected between a dedicated headset output wire and ground.  But for
> our own FreeCalypso headset I desire a different arrangement which I
> haven't seen used by any historical player other than iWOW: the
> arrangement I seek is to use a 4-wire TRRS plug, but still keep it
> monaural, with 2 non-ground wires used to connect the single earpiece
> speaker as a bridge-tied load.
> 
> My idea for the custom headset I'm seeking to get made came from iWOW.
> In addition to making a huge production run of TR-800 modules (so huge
> that I consider the NOS supply of these modules to be inexhaustible
> for the purposes of our community), they also made a small handful of
> their development board kits - but these iWOW development kits are
> much rarer than bare TR-800 modules, Das Signal and I found only two
> of them, and the two kits we have scored may well be the last two in
> the world.  On their development board, iWOW came up with the really
> neat idea of bringing out the *main* Iota audio channel to a headset
> jack - this idea is rather revolutionary, as the main audio channel is
> meant to be used for the phone's built-in earpiece and mic, whereas a
> typical finished phone's headset jack would normally be wired to the
> secondary or tertiary Iota audio channel.  But Iota's main audio
> output is differential and the phone's built-in earpiece speaker is
> meant to be connected to it as a bridge-tied load - thus a traditional
> 3-wire TRS headset cannot be connected to this main audio channel in
> the native and straightforward manner as pioneered by iWOW.
> 
> iWOW's solution was to replace the common 3-wire TRS headset with
> 4-wire TRRS, even though it is still monaural and NOT stereo.  The
> headset which iWOW supplied with their development boards has its
> earpiece speaker connected between Tip and Ring2 as a bridge-tied
> load, and the microphone is connected between Ring1 (positive) and
> Sleeve (ground).  But the problem with those iWOW-supplied headsets is
> that there are only two of them in the world: I have one, our dear Das
> Signal has the other, and there are no more.  My answer to this
> situation is to get more of these special headsets custom-made for us
> on a special order basis: I am the kind of person who will NEVER
> accept a no for an answer, and if iWOW were somehow able to get such
> unusual headsets, then we must do likewise.
> 
> Our Caramel2 board has its main audio channel brought out to a TRRS
> headset jack in iWOW's pinout just like iWOW's original DSK board,
> thus anyone who wishes to play with voice call audio on C2 will need
> one of these special headsets which I am now trying to get made.  But
> even more importantly, I plan to keep the same arrangement on our
> Venus board, i.e., bring out the main or primary Iota audio channel to
> a headset jack - thus the special headset will be a required accessory
> for FC Venus too.  I expect FC Venus to be a more interesting board
> than C2, thus the headset issue is now becoming a big deal.
> 
> Right now I am actively working on the headset issue, that is, looking
> for a headset manufacturer who would be willing to do what we need.
> So far I have reached out to two manufs by direct email; if I don't
> get a response from either of them, as the next step I will need to
> brave Alibaba's rather difficult web interface and post a buy request
> or RFQ or whatever they call it.
> 
> Hasta la Victoria, Siempre,
> Mychaela aka The Mother
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