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Why Freescale S12X? 
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TO220 - Visibile

Joined: Tue Apr 01, 2008 6:54 pm
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I know very little about microcontrollers (i'm a mechanical engineer), and I don't have a better idea either, but I would like the team to clarify why this family and manufacturer was chosen? Was it

a) Familiarity with the instruction set.

b) Availability of a good low-cost prototype board in the form of the ADAPT, which has all the essential development hardware, and only needs circuits for signal conditioning/protection/power regulation. For a project like this, I would think that this is more important that easy availability of the chip itself, which would prove useless to the home experimenter due to its non-DIP packaging.

c) Proven in automotive body electronics, and its sister the MC9S12C64 in megasquirt-2 hardware.

d) Availability of -40 to +125 rated chip as well should the need arise.

Why not Atmel AVR/AVR32? They are available in single quantities, are cheap, are known to have a good "performance-to-price" ratio, easy to get started with, and have a huge huge following in the DIY community too.

Not trying to shoot down anyone, just initiating a discussion on this specially since its bound to come up sooner or later.


Wed Apr 02, 2008 11:53 pm
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viewtopic.php?f=9&t=84

B,C,D, and also proven to have enough performance to do the job well reliably using the GCC tool chain.

Mainly B though as you noted. It sure reduces the entry cost time wise :-)

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Wed Apr 02, 2008 11:57 pm
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ADVANTAGES OF USING THE AVR’S
--------------------------------------------------------------
The latest AVR’s with more memory, code space and pin-out functionality
See the following links for the:
ATMEGA 1280
ATMEGA 1281
ATMEGA 2560
ATMEGA 2561

http://www.atmel.com/dyn/products/produ ... ATmega1281

With these new devices you can have up to 12 PWM channels

These devices are available with additional inputs and outputs so you have plenty of I/O

All of these are 100% code compatible with the Mega128

The new tools are free of charge

There is lots of support on the new http://www.avrfreaks.com

Very important [These devices are easily available even from Farnell’s and Digi-Key]

MOTOROLA DEVICES CONCERNS
--------------------------------------------------------------
Devices are difficult to get hold off, unless you are an OEM

Tools are very expensive unless you go for the user unfriendly GNU versions of the compilers

Support is very poor

The new devices are far too complicated

Devices are more expensive than the AVR’s

G&B


Sat Apr 26, 2008 10:28 am
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GrowlingandBiffo wrote:
The latest AVR’s with more memory, code space and pin-out functionality still do not have as much memory, code space, pins, or functionality as the FreeScale chips do
See bold above ^
Quote:
ATMEGA 1280
ATMEGA 1281
ATMEGA 2560
ATMEGA 2561
Max 100 pins
8 bit
16MHz
Quote:
With these new devices you can have up to 12 PWM channels
See the discussion where we decided we had enough hardware PWM already with just 8 and the other thread where I found a PWM expansion chip.
Quote:
These devices are available with additional inputs and outputs so you have plenty of I/O
100 pins max compared with 144 for xdp and 2XX for xep
Quote:
The new tools are free of charge
As is GCC 68hc11...
Quote:
There is lots of support on the new http://www.avrfreaks.com
http://www.google.com/search?hl=en&q=hc12%20forum
Quote:
Very important [These devices are easily available even from Farnell’s and Digi-Key]
Devices are difficult to get hold off, unless you are an OEM
Just not true. XEP is impossible to get hold of, but XDP should be
obtainable, provided the quantity is reasonable. I wonder how many units tech arts make...

http://octopart.com/search?q=MC9s12xdp512
http://octopart.com/search?q=MC9s12c128*

I rest my case!!
Quote:
Tools are very expensive unless you go for the user unfriendly GNU versions of the compilers
I don't see the 68hc11 package as difficult to use. Download the source, cd src, make, done. Then it's down to the code, which is just C and the same in the Linux kernel or Gaim/Pidgin or MTX or whatever else etc. I also don't think that any minor complexity is a big issue considering the type of people this site is intended for. Those willing to muck in and get their hands dirty.
Quote:
Support is very poor
See above
Quote:
The new devices are far too complicated
How? What is complicated? I haven't found anything particularly tricky other than misusing PIT timers for something they weren't designed for. You can hardly say "this IC doesn't have PIT, so the advantage is that it is simpler" or "hcs12x is more complex because it has PIT timers" as by default they are off, and you MAY use them at your OPTION. That is just not true. If you argue that they are more complex than required for EMS tasks, I will argue that you are not aware of what goes on inside an EMS.
Quote:
Devices are more expensive than the AVR’s
For a reason!!!! 16MHz @ 8 bit EVEN with RISC is no match for 40MHz, an 80MHz coprocessor, 16 bit CISC core. not at all. not even close.

To summarise, our core is just enough, it is not too much, it is not not enough, it is reasonably priced in the format we require or raw, the performance is there where it is not in the AVR family.

Most importantly is having a ready to use board that is appropriate for EMS use available easily and relatively cheaply. This is where the XDP shines with the Adapt board.

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Sat Apr 26, 2008 11:42 am
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Fred had addressed the points quite well, there is one more thing i'd like to add though:
for those not friendly with linux/unix ways, the Codewarrior is available for these chips with it's fancy environment and pretty good (from what i hear) compiler in both free evaluation and, i think, about $100 commercial license.

Maybe, if we make a worth pitch, Metrowerks will be kind enough to donate/sponsor our project with free Codewarrior licenses.

These chips' architecture is indeed more complex than the simple RISC cores, but the application dictates requirements on this and it's been proven that our application needs this level of complexity for good results. (MS1 vs MS2)

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Sat Apr 26, 2008 5:00 pm
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And the biggest reason is that we're already moving forward on it and that means it's too late to turn back now! :D

I've been evaluating other manufacturers solutions just out of curiosity and there doesn't seem like there is many out there that are really superior to the S12X for all the things we're looking at.


Sat Apr 26, 2008 5:54 pm
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That is a big one too! :-)

For me, the form factor is the main thing though. The Adapt board is perfect for integration into a custom project like this. The XEP board is half the price, but is not suitable for just plugging into a custom project...

The keen among us later might desolder our xdp and solder on an auto rated xep with the same pin count and pin layout and pick up some more performance and more timers.

Or we could just design a new CPU board for diyers to build that uses the XEP part.

A further reason will be MS3 compatibility also. It will be nice if MS users have an alternative code base to choose from. Staying compatible pinout wise with out independent code will be a good move for sure.

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Sat Apr 26, 2008 6:10 pm
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LQFP112 - Up with the play

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As if you think those guys would let something like that fly...

You can't use their code on other hardware, what makes you think they'll let other code run on their hardware?

That would completely undermine everything they have done of course!


Sat Apr 26, 2008 6:41 pm
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That is not their choice!!! :-) I'll definitely be porting whatever I have to XEP when MS3 comes out IF it uses that type of CPU... If it doesn't then... who knows what will happen :-)

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Sat Apr 26, 2008 6:42 pm
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