[Coco] OT: Cheap controller chips
fwp at deepthought.com
Fri Sep 30 15:43:14 EDT 2011
I like the idea of free running PWM! How many PWM oscillators does the picaxe
have? The reason I ask is that as you know the control signal for RC servos, etc
is PWM and there is an increasing number of drivers that have an "RC input". While
the propeller has a number of hardware timers (2 per cog for a total of 16) that
can generate pulses of various lengths there are no "free running" oscillators.
As anyone that knows me knows I believe that there rarely a single best way to do
something and in the case of microcontrollers I think different chips are better
suited to some tasks then other. As a result I like to try a lot of different things
so I can choose which is best for a given situation. I'm looking forward to try the
picaxe and putting it through it's paces to find what it's best suited for and not so
well suited for. I can already think of a number of things that a propeller wouldn't be
a natural fit for.
You may want to take another look at the propeller and keep it in mind for larger projects.
There are several basic compilers now available although in my never humble opinion
the best is "propbasic". The goal of it's developer is to provide the ease of use of the
basic used by the basic stamp without losing any of the capabilities or power of the
propeller. There is a elaborate<SP?> set of rules about the use of the I/O pins but that's
a requirement stemming from allowing 8 cores (called cogs) direct access to all of them. My
issue with the propeller is the crazy "hub system" it uses to allow access to shared
resources and the lack of hardware interrupts.
The Other Frank
On Fri, Sep 30, 2011 at 08:49:46AM -0700, Steve Bjork wrote:
> Hi Frank,
> I too look at the 8 core Propeller chip and found it a bit of work
> to get up and running. At the time, there was no free BASIC
> compiler. (Just a free C compiler.) There was also a bit of
> weirdness with the I/O ports because of the 8 cores. This kept me
> jumping on the Propeller chip back then.
> The PICAXE uses a BASIC that is very much like Basic Stamp. (Easy
> to use.) You can run two task at once. (Just like having two
> cores.) Build in PWM, timers ADC and servo controller hardware.
> Yes, I said hardware. The PWM and Servos commands start the
> operation for the hardware to drive (and refresh) the timing to the
> lines. (Nice.) The chips can run at 32 Mhz.
> For what I doing with my Halloween display, PICAXE has worked out
> well because of its low price and ease of coding.
> Frank, thanks for you input on this subject.
> On 9/29/2011 1:11 PM, Frank Pittel wrote:
> >Very cool and thanks for the info and link. Just a month ago I bought into
> >the Parallax (maker of basic stamp) Propeller. It's a nifty little microcontroller
> >with 32 I/O pins (4 dedicated during startupt but general purpose after that) 8 cores
> >all running at 80Mhz and is available for $7.99 in single quantities. After I spend
> >sometime with it I'll be taking a look at the picax.
> >For now though I have a couple of projects that I'm working on that will is being built
> >around the propeller which is taking up all my "puttering" time.
> >The Other Frank
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