GTM900 support update

Serg l serg at tvman.us
Tue Jun 18 15:08:40 UTC 2019


Thank you Mychaela, this pretty nice platform as an alternative to C1xx
phones. While it is not as robust as FCDEV3B, it makes it a usable platform
for some applications development.
I have done a quick search for a dev board schematics and here is an easy
find.

http://read.pudn.com/downloads341/sourcecode/windows/comm/1491896/%E5%8D%8E%E4%B8%BAGTM900%E5%BC%80%E5%8F%91%E6%9D%BF%E8%B5%84%E6%96%99/mg_gtm900%E5%BC%80%E5%8F%91%E6%9D%BF%E5%8E%9F%E7%90%86%E5%9B%BE.pdf

On Mon, Jun 17, 2019 at 10:32 PM Mychaela Falconia <
mychaela.falconia at gmail.com> wrote:

> Hello FC community,
>
> Earlier today I have added GTM900 target support to our FC Magnetite
> firmware.  You can compile FC Magnetite for the gtm900 target, flash
> the resulting image into the module with fc-loadtool -h gtm900, and
> you will have a GSM+GPRS modem module running FreeCalypso firmware
> instead of Huawei's, with approximately the same functionality as the
> original, but with a known corresponding source.
>
> I have only done a limited amount of testing, limited by crippled
> hardware: the job of adding GTM900 target support to Magnetite took a
> few hours, whereas designing and building my desired breakout/interface
> board for these GTM900 modules would be a weeks/months task.  The
> limited testing I have performed was done using Songbosi's simple FPC
> breakout board (turning each FPC pin into a 2.54 mm header pin without
> further intelligence), and a very weak power supply arrangement: per
> Songbosi's recommendation I took just one out of the provided 5 power
> pins and connected it with a female-to-female "Dupont" jumper wire
> (probably 28 AWG, i.e., totally unsuited for carrying any substantial
> power supply currents) to the +5V pin on the PLDkit FT2232D breakout
> board I was using to connect the two UARTs.
>
> Feeding +5V to Calypso GSM devices (both to the core chipset and to
> the PA) is not too terribly bad if done for short periods of time (the
> chipset is designed to tolerate such high VBAT because according to
> TI's docs, NiMH 3-cell batteries can reach a little above 5V during
> charging), but the real problem is that by connecting only one power
> pin out of 5, using a 28 AWG wire and using USB as the ultimate power
> source, this hacked-up arrangement deprives the modem of the current
> capacity it was designed for.  The proper solution as I see it would
> be to design and build a more proper breakout/interface board that
> connects directly to the FPC interface and connects all 5 power and
> GND pins with sufficiently thick PCB traces to a proper power input
> connector like the big orange one on TI's historical development
> boards and on our FCDEV3B, but of course it is more than a one weekend
> job.
>
> Amazingly enough, this cheap power arrangement worked well enough to
> allow me to test RF Tx: I used Songbosi's little RF adapter that
> converts the module's antenna port to SMA, connected it to our CMU200
> instrument and ran fc-rfcal-txcheck against both Huawei's original fw
> (yes, our tools work against Huawei's fw, that's how little they
> changed from TI's baseline) and our own FC Magnetite on this module.
> Our Magnetite fw runs with Huawei's original FFS on this target, and
> the numbers reported by fc-rfcal-txcheck are the same between the two
> firmwares, so it looks like we got the RF part right.  I have not
> tested the SIM interface or any end user modem functionality for which
> a SIM is required because I don't have a SIM socket hooked up to the
> "dumb" breakout, only power and the two UARTs.  However, since I have
> verified with my CMU200 setup that the RF Tx output is in compliance
> with regulations, it is now safe for other people to test FC Magnetite
> on these GTM900 modems, including people who don't have their own
> cabled test BTS setups and can only operate in open air.
>
> Going forward, I am hoping to get the fc-host-tools-r11 release out in
> another week or two (all major code and documentation work is done,
> just a couple of minor bits left), and I need to sync the recent
> Magnetite fw developments into Selenite: not only the addition of
> GTM900 target support, but also MEMIF changes which affect all targets
> - see my new MEMIF-wait-states article in the freecalypso-docs Hg
> repository.  Then I will do some more work on the Calypso JTAG
> subproject (need to do some experiments with EMU0/EMU1 pins and some
> ideas as to how it might be possible to halt the Calypso ARM7TDMI core
> directly out of reset), and after that I will need to start working on
> little hardware projects.  As to the latter, I have 3 of them in mind:
> DUART28 (USB to dual UART adapter with 2.8V I/O), FC-UJA (FreeCalypso
> UART+JTAG adapter, a prerequisite for my FC handset board idea) and
> the more complete breakout/interface board for GTM900 modules.  The
> order in which I am going to work on those little hw projects is
> subject to change at any moment based on my mood and feelings. :)
>
> Hasta la Victoria, Siempre,
> Mychaela aka The Mother
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