+
−Back when TI's TCS211 fw existed in the traditional world of phone handset and
+
−cellular modem manufacturers, there were only two principal classes of target
+
−devices for it: handsets and modems.  The former have local UI hardware (LCDs
+
−and keypads) and run firmware that works with this UI hw, the latter have no
+
−such hw and run firmware that expects to be controlled by an external host via
+
−AT commands.
+
−
+
−But the peculiar circumstances under which our FreeCalypso family of projects
+
−operates give rise to a third possibility: what happens if one were to run
+
−non-UI-capable firmware that expects control via AT commands on a hardware
+
−target device that was originally designed to be an end user phone handset, in
+
−our case either Motorola C1xx or Pirelli DP-L10?  The result is what I call a
+
−voice pseudo-modem (VPM): the phone's LCD stays dark, the buttons do nothing
+
−and the device expects to be controlled via AT commands as if it were a modem
+
−like the one in GTA01/02 smartphones, but there is no practically usable way to
+
−make use of any data services, only voice and SMS, hence my VPM term.
+
−
+
−It needs to be noted clearly that the VPM hack described in this article is NOT
+
−a substitute for proper modem hardware - if your area of interest is Standard
+
−Modem functionality (the full set of GSM and GPRS services accessed via AT
+
−commands), then you need a proper hardware platform for it, such as our FCDEV3B
+
−hardware product.  However, support for VPM operation in FreeCalypso exists for
+
−the following purposes:
+
−
+
−* On some hw targets the VPM configuration can be an intermediate stepping stone
+
−  toward potential future UI-enabled firmware (see the Handset-goal article) -
+
−  this situation holds on the C139.
+
−
+
−* Being able to run FreeCalypso fw in the VPM configuration on Mot C1xx hw that
+
−  many people already have and that may still be readily and cheaply available
+
−  makes our firmware accessible to those who are not able to afford our
+
−  expensive FCDEV3B hardware.
+
−
+
−* If you have a Pirelli DP-L10 phone (now very rare and hard to get, but were
+
−  readily available in early 2013 when I started FreeCalypso): while there is
+
−  unfortunately very little chance of being able to turn it into a practically
+
−  usable Libre Dumbphone with FreeCalypso (the unwanted extra chips sans docs
+
−  which we don't know how to power down are a killer), running FreeCalypso fw
+
−  on the Pirelli in the VPM configuration is so easy and convenient that I do
+
−  it all the time during development and testing.
+
−
+
−Building firmware for VPM operation
+
−===================================
+
−
+
−The following two firmware build configurations (in the ./configure.sh sense)
+
−are appropriate for VPM usage:
+
−
+
−hybrid-vpm	This is the TCS2/TCS3 hybrid config (see the Modem-configs
+
−		article) that has all data services (CSD, fax and GPRS)
+
−		disabled and FCHG (new FreeCalypso battery charging driver)
+
−		enabled.  The removal of data services code makes the firmware
+
−		image size and its RAM usage significantly smaller than all
+
−		other configurations, making hybrid-vpm the smallest of all
+
−		FC Magnetite firmware configs.
+
−
+
−l1reconst-chg	This is a variant of the stable l1reconst config (again, see
+
−		the Modem-configs article) that has our FCHG battery charging
+
−		driver enabled.  Because this config uses the TCS211 blob
+
−		version of the G23M PS, data services cannot be disabled, and
+
−		the associated code sits in the firmware image as dead weight.
+
−		Thus this l1reconst-chg config produces much heavier fw images
+
−		than hybrid-vpm, and should only be used when you suspect a bug
+
−		in the new TCS3 G23M or ACI code and would like to run the old
+
−		TCS2 version for comparison.
+
−
+
−Mot C139/140 and C155/156 phones have enough flash and RAM to run the
+
−l1reconst-chg config (with data services code as non-exercisable dead weight),
+
−but the more basic C11x/12x models (the ones with black&white LCDs) have
+
−smaller memories, and the only FC Magnetite config that is small enough to fit
+
−into their tiny flash and XRAM capacity is hybrid-vpm.
+
−
+
−Playing with FreeCalypso VPM on C1xx phones
+
−===========================================
+
−
+
−If a Mot C1xx phone is flashed with a FreeCalypso firmware image in the VPM
+
−configuration (see C1xx-Howto for the messy details of how to do it), it will
+
−behave as follows:
+
−
+
−* The LCD will remain dark and the buttons will do nothing no matter what.
+
−
+
−* If you plug in Motorola's charging adapter (it's a regulated 5 VDC power
+
−  source, but with a non-USB connector) and you had properly installed the
+
−  charging config file when creating the aftermarket FFS for FreeCalypso, the
+
−  battery will charge.  When you unplug the charging adapter, if there is no
+
−  host computer running FC host program rvinterf connected to the phone
+
−  serially, the phone will power off some 15 to 20 s after the charger unplug.
+
−
+
−* If you press the power button while the phone is off, even momentarily, the
+
−  phone will power on and boot (with nothing on the LCD as usual), but if the
+
−  headset jack serial port is not connected to a computer running rvinterf, the
+
−  firmware will execute a power-off after at most 20 s.
+
−
+
−* In order to make the phone-turned-VPM do anything useful, you will need to
+
−  connect the headset jack serial port to a host computer running FC host tools,
+
−  run rvinterf to keep the phone alive (keep it from automatically powering
+
−  off), and use FC host utility fc-shell to issue AT commands to it over the
+
−  RVTMUX channel managed by rvinterf.
+
−
+
−* The phone will remain on (i.e., the fw won't execute an automatic power-off)
+
−  for as long as there is either a charging power adapter plugged in or a
+
−  connected host computer running rvinterf - if there is no charging power,
+
−  the fw will send periodic keepalive queries to check for the presence of a
+
−  connected rvinterf process.
+
−
+
−Playing with FreeCalypso VPM on a Pirelli DP-L10
+
−================================================
+
−
+
−There are two ways in which one can play with FC VPM firmware on a Pirelli:
+
−
+
−* FC VPM fw can be flashed into the phone just like on Mot C1xx.  To make this
+
−  approach sensible, you will also need to craft and install a charging config
+
−  file that will cause our FCHG driver to initiate the charging process
+
−  automatically when the battery voltage falls below some sensible threshold,
+
−  without requiring manual charging start via AT@CHG=1.  In this case the
+
−  reflashed phone will behave like C1xx in the previous section, except that
+
−  the charging power source and the host computer connection are one and the
+
−  same in the case of Pirelli's USB.
+
−
+
−* The other approach is to keep Pirelli's original fw in the flash, let the
+
−  phone function normally when not in the middle of a FreeCalypso VPM session,
+
−  and load our FC VPM fw into RAM via fc-xram, making use of this phone's huge
+
−  RAM that can hold an entire functional fw image without flashing.  This is
+
−  the Mother's preferred method.
+
−
+
−See the Pirelli-Howto article for the details.