ARM DATV

No picture today but I thought you might like to know that the tests that
Rob M0DTS has been doing using an MK808 have been quite successful.
The module that uses the most CPU cycles is the Reed Solomon encoder.
Luckily Brian G4EWJ has written an optimised version of this module
in ARM assembly language. His module uses about 1/4 of the processing
that my C module does. So we have managed to get the whole thing down
from 60% to about 20%. There are further improvements that can be made.

I may have a go at optimising my C code as it is nice to have something that
can be ported to other Linux platforms.

The bare DATV-Express boards have been fabricated and the last I heard is
that they are with the courier.

I am hoping that the DATV-Express project can become a collaborative one
at least as far as the software is concerned. It may not be possible for everyone
to hand solder SMD components these days but everyone can try to write some
software. For small projects like this it is not that difficult and we all have to
start somewhere.

Software Modules

This week I have been playing with a modularised version of my DATV host software
with the help of Rob M0DTS. This allows the software to be run on small embedded
processor boards like the inexpensive ARM based MK808 media player or even the
Raspberry PI. To get some idea of the size of the MK808 I have posted a picture of it
above. It is a dual core ARM A9 processor running at 1.6 GHz. I paid £32 for the
MK808 from China but they can be got for £39 from the UK. It is necessary to
replace the Android software with Ubuntu Linux, Rob used the Picuntu distribution.
As these things can be dual booted you don't loose Android.

I don't have a Digilite and the new DATV-Express hardware is not ready yet so Rob
did the actual testing of the software. He managed to transmit a 4MS/s DVB-S
DATV signal using a MK808. For input he used a PVRUSB2 and the output a
Digilite. So I think we have shown you don't need a Windows PC to transmit
DATV anymore. While I don't expect the Raspberry PI to be fast enough to work
with a Digilite it should be fast enough to work with DATV-Express as a lot of the
heavy lifting will be done inside the FPGA.

Terry G1LPS intends to use an MK808 as part of the 3.4 GHz output on GB3KM.

The code consists of a number of small modules than can either run on an
embedded processor board or as part of a DATV application running on a standard
P.C.

I am thinking of converting the modules into GStreamer objects mainly because a
number of manufacturers only allow access to their GPU accelerated video engines
via GStreamer.

I still have to look at the receive side. Most of the Linux based media players are
aimed at broadcast TV and they are not particularly Amateur Radio friendly as far
a setting up is concerned. GStreamer provides video display windows that can be
embedded inside your own applications so putting together an Amateur Radio
friendly receive system should not be too difficult. I may leave this as a project
for someone else.

Sabre Lite - DATV-Express - Interesting SDR

I recently purchased from Farnell a Freescale Sabre Lite board (see above).
I removed the supplied OS and now have Linaro Linux running on it.
This has a Quad core ARM processor on it with each core running
at up to 1 GHz. It also has 1 Gb RAM and interestingly a 24 bit RGB input port.
The hardware H.264 encoder will encode 1080P at 30 fps and decode at 60 fps.
I plan eventually to port my DATV code to this and use it in conjunction with a
DATV-Express board as a standalone DATV system. There is no MPEG2 on it
but I understand it is capable of encoding MPEG2 in software in real time using
GStreamer plug ins.

Which nicely takes us on to DATV-Express, the board design files have been sent to
the manufacturer and should be ready on the 21st of February. Then they will need to
be hand populated.

Finally I was made aware of this Kickstarter project  bladeRF which looks very
interesting, it would be fully capable of doing DATV. What makes it interesting is the
LimeMicro LMS6002D chip which integrates the RF, mixers, Anti-alias filters and
ADC/DAC onto one chip and which will operate at up to 3.8 GHz. I am tempted as I
could easily move my DATV code to run on it. I wish them well with the project.
Now if they could only get the price down :)