[aprssig] APRS telemetry and the PIC 16F877A
Jason Winningham
jdw at eng.uah.edu
Thu Jan 25 21:19:31 EST 2007
On Jan 25, 2007, at 4:57 PM, Dave Baxter wrote:
> There is nothing wrong with the Atmel chips, but the CPU
> architecure you could argue harks backwards in time,
Atmel has (at least) two architectures, the 8051 and the AVR. The
AVR is a fairly modern architecture, designed by some college
students somewhere in northwestern Europe, IIRC (Norway? maybe
Sweden?). The 8051 is certainly "mature". (:
> PIC's and RISC archetcture, looking forward by comparison?
Gotta watch the PICs because many, especially the low end devices,
require multiple clock cycles to execute a single instruction (in
_spite_ of the fact it's RISC). A 20MHz 16F628 is actually executing
instructions at 5M instructions/s, where the AVR family uses a single
cycle per instruction, so you're getting 16M instructions/s with a
16MHz device.
If there are free PIC compilers, it's happened since I gave up on
them. I'll stick with the AVR all the same.
To keep this on topic, a couple of years ago N4TXI built a tracker
based on the AVR called WhereAVR. It generated APRS packets ala TT/
OT, but he also implemented a zero crossing detector to _decode_
packets. He used it to fire a cutdown mechanism on a high altitude
balloon by sending a message from his D7.
-Jason
kg4wsv
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