revisiting the 434 MHz band

Wolfgang Spraul wolfgang at sharism.cc
Fri Jul 23 23:04:00 EDT 2010


Werner,

> > I'll try to understand the MAX2830 you pointed out, if you find out more
> > please keep sharing...
> 
> I think it's still too low-level for our purposes. That is, unless
> there's some nice chip around that picks things up at the analog
> I/Q level and produces at least the bit stream. (And vice versa in
> the transmit direction.) From there on, a CPLD/FPGA should be able
> to do the rest without too much suffering.

No no, not hookup to an FPGA. Even the MAX2830 is still too low-level to
work without an FPGA? I definitely want to hook this up to a regular
ASIC XBurst CPU. In a future NanoNote, it is very likely we will have two
cores in the XBurst. There is also a set of SIMD instructions that may
help with some computations. Maybe we can run a real-time kernel/OS in
the second core, to deal with the RF protocol?

I was encouraged to look into SiGe chips by Henry Hallam
(http://www.pericynthion.org), who says he works on a solution with a Blackfin
DSP and SiGe SE4120L to implement the GPS stack, and he thinks it might be doable
with a non-Blackfin as well. Hopefully he will release sources soon.

So back to MAX2830, definitely we should find an RF chip that we can hookup
directly to an XBurst, like I said maybe the maximum would be to have a
dedicated core in the XBurst run a real-time protocol to talk with the RF
chip.

> I'm not sure 802.11b/g is a realistic target for the Ya with this
> sort of approach. I'd see a much better chance for getting things
> right in time with IEEE 802.15.4.

The one thing that worries me about IEEE 802.15.4 is the range. Only a
few meters? That's what I still like about 433 Mhz - it seems to work over
hundreds of meters, possibly even more...

Wolfgang




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