[Freetel-codec2] DMR portable - firmware replacement possible

[Simon Wood]

Hi all,
It looks like Travis Goodspeed is being mighty neighborly... and has
reversed the update process _and_ firmware of the MD380 DMR-talkie enough
to allow complete control and re-programming of the radio.

http://phasenoise.livejournal.com/1142.html

This might be a _really_ good target for a VHF/UHF Codec2 project.
Simon.

--------------------
Feb 01
Simon Wood
@mungewell

@travisgoodspeed Awesome work on the MD380! You mentioned possibility of
other protocols, is there enough juice to implement (open) CODEC2?
--------------------
Feb 01
Travis Goodspeed
@travisgoodspeed

@mungewell Probably yes. Codec2 has already been ported to the STM32F405
and the AMBE emulator code is isolated to its own thread.

[Brady O'Brien]

It's probably possible to get something running on it, but it looks like
the MD380 uses the same sort of analog FM+DSP mod/demod architecture that
most of these digital VHF/UHF radios do. We're targeting a more direct SDR
approach with the SM2000 and VHF FreeDV, as the analog FM+DSP leaves a lot
of performance on the ground (see http://www.rowetel.com/blog/?p=4650).

Post by Simon Wood
Hi all,
It looks like Travis Goodspeed is being mighty neighborly... and has
reversed the update process _and_ firmware of the MD380 DMR-talkie enough
to allow complete control and re-programming of the radio.
http://phasenoise.livejournal.com/1142.html
This might be a _really_ good target for a VHF/UHF Codec2 project.
Simon.
--------------------
Feb 01
Simon Wood
@mungewell
@travisgoodspeed Awesome work on the MD380! You mentioned possibility of
other protocols, is there enough juice to implement (open) CODEC2?
--------------------
Feb 01
Travis Goodspeed
@travisgoodspeed
@mungewell Probably yes. Codec2 has already been ported to the STM32F405
and the AMBE emulator code is isolated to its own thread.
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[Steve]

I think the most important design aspects for VHF voice is continuous tuning.

You don't want channelized CB operation. In HF we usually stare at our
panoramic displays and put the pipper on the signal. We may scoot our
signal right next to some other guy. Maybe in the future, we will have
a modem that can decode two signals at a time (a la PSK31) :-)

The FDM modem is neat, in that it can track any slow drift. This drift
is almost insignificant at HF, but noticeable at VHF. As the radio
warms and cools, it goes up and down in frequency. Adding temperature
stabilization at the LO costs money, and heck, if the modem can adjust
fast enough, who cares what the exact frequency is.

Back in the 90's when I ran a couple of D4-10 radios from Kantronics,
they were basically worthless, as the two LO's would drift at
different rates. The radios were simplified direct FM, with a data
slicer. No way to modify them, except disconnect 90% of the radio.

I think the SM2000 would be a lot of fun, even without spending a lot
of money on frequency stability. Well, I mean, it couldn't drift by
10's of kilohertz, but even if it did, we could turn the dial a tad as
we listened.

[Bruce Perens]

Here's what I think should be the stock reply about the MD380:

*The MD380 is interesting, and Codec2 can be ported to it, but it would
fall short of providing the full benefits of Codec2. Codec2 is capable of
substantially narrower bandwidth for the same voice quality, and with the
narrower bandwidth come greater clear voice range or greater battery
savings (pick one) and at least five channels in the space a wider
bandwidth HT uses for one. To do this, you need a modulator and demodulator
that work efficiently at narrower bandwidth, and greater frequency
stability.*


Being able to lock on a base station that indicates a higher-precision
oscillator may be helpful for mobiles. Even a high-precision crystal can
drift the width of one of our narrow channels at 440 MHz.

I don't think we need finely variable frequencies for anything but
satellites. For terrestrial use, we just need narrower channels and a way
to make our frequency precise. But internally, our synthesizers provide
more fine adjustment of frequency than channelized systems would generally
use.

Bruce

Post by Steve
I think the most important design aspects for VHF voice is continuous tuning.
You don't want channelized CB operation. In HF we usually stare at our
panoramic displays and put the pipper on the signal. We may scoot our
signal right next to some other guy. Maybe in the future, we will have
a modem that can decode two signals at a time (a la PSK31) :-)
The FDM modem is neat, in that it can track any slow drift. This drift
is almost insignificant at HF, but noticeable at VHF. As the radio
warms and cools, it goes up and down in frequency. Adding temperature
stabilization at the LO costs money, and heck, if the modem can adjust
fast enough, who cares what the exact frequency is.
Back in the 90's when I ran a couple of D4-10 radios from Kantronics,
they were basically worthless, as the two LO's would drift at
different rates. The radios were simplified direct FM, with a data
slicer. No way to modify them, except disconnect 90% of the radio.
I think the SM2000 would be a lot of fun, even without spending a lot
of money on frequency stability. Well, I mean, it couldn't drift by
10's of kilohertz, but even if it did, we could turn the dial a tad as
we listened.
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