GTM900 support update

Mychaela Falconia mychaela.falconia at gmail.com
Mon Jun 10 20:36:49 UTC 2019


Hello FreeCalypso community,

Last week I received a few GTM900 modules from Songbosi, and yesterday
I finally got around to powering one of them up using the included FPC
breakout board.  Both Calypso UARTs are indeed brought out on this
module, and both of them work.  The original firmware presents an AT
command interface on the MODEM UART and TI's RVTMUX interface on the
IrDA UART just like mainline TI/FreeCalypso firmwares; Huawei's
version of the RVTMUX interface features the same level of trace
verbosity as our TCS211 reference version and supports ETM commands
for reading and writing memory and registers, i.e., fc-tmsh works just
fine against Huawei's fw.

The current version of fc-loadtool in the freecalypso-tools repository
now supports flash operations on these GTM900 modules.  The new target
is -h gtm900, telling the Calypso boot ROM to run the ARM7 core at
52 MHz and sensibly configuring MEMIF registers, whereas newly added
support for the flash part of the K5L3316CAM MCP (the combined
flash+RAM chip used in these modules) resides in the fc-loadtool
binary itself.  The new flash handling architecture in fc-loadtool as
of two weeks ago is based on a hard-coded table of all supported flash
chip types, designed to grow easily as new devices are found, plus an
autodetection mechanism that selects among these supported flash chip
types based on the ID codes read from the chip.

The next step for me is to put out a new release of FC host tools.  I
still need to finish documenting some of my earlier changes (in
particular the documentation for the target-utils suite needs to be
finished), and when I am done with this documentation work and maybe a
few more minor code changes, we'll have the release.

After we get the next FC host tools release out that includes GTM900
support and other recent developments (the most interesting is the
manipulation of the undocumented register in the Iota ABB to fix the
erratic behaviour seen in the test reset, then poweroff, then PWON
sequence - see Calypso-test-reset article in freecalypso-docs), before
I go to the next step of adding GTM900 target support to our Magnetite
and Selenite firmwares, there will be an intermediate step of producing
a better breakout board for these GTM900 modem modules.

The way I see it, the motivation behind providing full FC support for
these GTM900 modems is to allow these very cheap modules to serve as
a much cheaper alternative to our expensive FCDEV3B, making our
FreeCalypso sw/fw offerings accessible to those who cannot afford our
high-end hardware.  To make such usage possible, we need a better
breakout board for these FPC-interfaced modems - not just a dumb
breakout board that turns every FPC pin into a 2.54 mm pin 1:1, but a
more purpose-made one.  My idea to build a breakout or interface board
that will have the SIM socket, PWON and RESET pushbuttons on the board
itself and provide the same connectors for power and for the dual UART
as on the FCDEV3B.  I plan on working on this breakout or interface
board design after the FC host tools release.

Hasta la Victoria, Siempre,
Mychaela aka The Mother


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