GTM900 support update

[Serg l]

I also found this document which describes some other variants of GTM900.
Looks like 850/1900 band is supported in GTM900-P

https://drive.google.com/file/d/1njpHGLtLHQhttGL5XkqQhGiTcs4CBYds/view?usp=sharing

I'm going to get one and decap.

On Tue, Jun 18, 2019 at 11:08 AM Serg l <serg at tvman.us> wrote:

> 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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>