I agree that the lack of FPU means it's a lot harder to support all the
software that would ideally live in a baseband modem. I'm not clear what
the solution is yet, except that the fixed point gmsk modem could make it
into the baseband processor. At this point, my plan is to offer up this
project I've been working on: schematics, source, and docs as open source.
Hopefully, lessons will be learned and some part of this will be valuable
to the community at whole.
The board that I'm manufacturing for Hamvention is a full-duplex
quadrature-bits to RF board with sleep states in mA range (10 bits
resolution). Operating range should be 5MHz to 1000MHz w/ 1MHz bandwidth,
though right now you'll have to change parts on a few matching networks to
optimize signal integrity for a given band. Based on the CMX991, it fits
in a 38mmx57mm "room" at 3.3V. This could be connected to any processor
you want to try.
The baseband processor I'm trying is an ARM Cortex-M3 SoC processor that
has an integrated FPGA called the SmartFusion. This is doing DSP to/from
the quadrature rf transceiver. I think the SmartFusion is a really
interesting hybrid chip that allows for low power sleep modes and the
agility of a reconfigurable radio, with Linux in the package. In practice,
I think the FGPA will end up being a co-processor for FIR, IIR, FFT just
like the functions in the SHARC DSP.
I'm into creating an open project, and both Verilog and ARM C have cross
vendor support. There's ARM SoC FPGA's from Xilinx Zynq, Actel
SmartFusion(2), and very recently Altera Cyclone V. Expect the SDR
manufacturers using FGPA's to come out with radios built on these chipsets.
I definitely think you could hook up a DSP processor but I'm not sure which
one to try. I'd be interested to see your results.
Chris KD2BMH
On Wed, Apr 17, 2013 at 5:13 AM, Greg Troxel <g...@work.lexort.com> wrote:
>
> I know the Elecraft KX3 is not Open Source, but it's interesting to look
> at the CPU choices because it does an amazingly good job at
> functionality per dollar and per watt. There's an 18F87K22 and an AMD
> floating point DSP (ADSP-21479) and no conventional CPU. It manages to
> receive HF with 200 mA. For a handheld, battery life is going to be a
> huge consideration. So if I were going to build something that was like
> an FM handheld and also had DV (and probably a GPS chip and APRS, like
> the VX8), I'd avoid SDR and put the codec2 modem in the DSP.
>
>
> http://www.analog.com/en/processors-dsp/sharc/ADSP-21479/products/product.html
>
> My guess is that once codec2 is on that DSP, and maybe the container
> protocol (like D-STAR) replacement, then the PIC can do the rest of the
> UI.
>
>
>
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