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Why 16BIT? Why Not 32BIT? 
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TO220 - Visibile

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As per the title. The aim of FreeEMS is to make a high performance EMS so was it ever considered to go to a 32bit controller? I understand that cost may have been a factor but are there any other reasons?

Cheers

Daniel


Thu Mar 06, 2008 2:08 am
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Primarily cost and form factor. The advantage to the Adapt board is that it could be used in-car right now with little/no mods and an appropriate main board. Another major factor is GCC availability for the core. Also, once we are more underway, these chips are available in high temperature packages if we should decide to produce a similar plug in card specifically for our purposes (though I doubt we will). Finally, I had to make a decision and order something, and that unfortunately that was before this forum etc existed.

Although FreeEMS is going to be Freescale 16 bit, there is nothing to stop you using this environment (forum/site) to start a parallel project with a different core/board base. I fear that doing so could fragment development effort and basically ruin the whole idea, but never the less, I won't try to stop you if you should decide to do that.

I think that it has been well established that the 16 bit cores can do sufficiently fast and accurate math with care in the programming department.

Which 32 bit cores (and boards!) did you have in mind? Regardless of where we are at, I'm keen to learn about them :-)

It's certain that one day there will be a FreeEMS Mark 2 and when that time comes, it will be a community decision in the spirit of the site as to what is used for that project :-)

Fred.

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Thu Mar 06, 2008 8:38 am
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I didn't have a processor in mind and I have nothing against using a 16bit. I just thought I would post the question to see peoples thoughts on the topic.

Cheers

Daniel.


Thu Mar 06, 2008 10:45 am
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OK, no worries :-)

For reference the mpc555/mpc555x development cores cost about 5x as much+. I think I saw the 68332 in at around that price point too. It's a big jump up :-)

I didn't investigate the ARM offerings, but perhaps I should have.

Either way, I'm quite a fan of "tried and true" and James/Ken have proved that GCC+hcs12 is a capable setup. We are just taking that to the next level speed and I/O and openness/freeness wise :-)

Fred.

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Thu Mar 06, 2008 1:48 pm
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RE: 16bit vs. 32bit

baby steps, baby steps... (let's learn to crawl before we try to fly to the moon!)


Sat Mar 22, 2008 3:14 am
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Hi Rob :-) Having faster gear means less work involved in making it do the job required. However, we need to be realistic about needs and requirements and costs and so forth. I think it's the right choice overall at the current time, mainly because of the VERY usable packaging if nothing else.

26 Chevy, my apologies if I was a bit defensive with that initial response. I guess I must have just read it as a criticism that it just wasn't in reality :-) Sorry.

Fred.

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FreeEMS dev diary and its comments thread and my turbo truck!
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Sat Mar 22, 2008 1:18 pm
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Quote:
Which 32 bit cores (and boards!) did you have in mind? Regardless of where we are at, I'm keen to learn about them :-)


Hi,
the new MPC5633M from Freescale is in my opinion a suited device for DIY powertrain:
- compatible to exsiting MPC55xx PowerPC familiy
- 144pin LQFP
- plenty of processing power for the future
- dedicated timing processor (ETPU) with built in support for angle clock
- precompiled libraries for crank, cam and much more
- signal processing instruction set for fast knock detection algorithms or table lookup
- configurable hardware iir/fir filter with decimation
- pretty fast ADC
- DMA system
- free available GNU compiler
- opensource OS called ECOS could probably run on it

I've been using a S12XF including XGate in the past year on my own ecu project. After switching to the MPC5633M I must say it's much more comfortable to leave the memory banking and the other constraints like 16-bit timers and missing DMAs behind. Power architecture is complex but you save a lot as it's intended use is powertrain and therefore a lot of stuff already exists. For a 1 or 2 cyl. engine a 16bit processor is ok in our days but since 32bit gets cheaper and cheaper.


Thu Oct 02, 2008 6:48 pm
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I've got a 68332 MRM board lying around - it was only about $100 when I bought it - so not very expensive at all - only problem being that the processor is 32bit but the MRM mainboard was designed with 8bit ram so they really stuffed that up good - ie it takes 4 retrieve cycles to get anything from ram - and ram is much slower than the cpu so it really slows things up if you ask me. Although I've never had a problem with it being to slow for anything I've used it for so perhaps thats a misnomer.


Thu Oct 02, 2008 7:42 pm
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Movex wrote:
Quote:
Which 32 bit cores (and boards!) did you have in mind? Regardless of where we are at, I'm keen to learn about them :-)

the new MPC5633M from Freescale is in my opinion a suited device for DIY powertrain:

That's great, but you missed the bit in bold. For this to be fairly successful it needs to be easily accessible to those without the skills and abilities to solder fine pitch gear. Additionally, the proto board of choice needs to be physically suitable for plugging into some main board.

I haven't seen anything with the pin count and modular design that is suitable, but I'm interested to see what is out there.

Having said all that, the site needs a successful project and a modest one at that. Something that works, works well and is fairly basic and cheap. After that is off the ground I expect all sorts of parallel projects to spring up. Till then we need to focus on one thing and someone had to choose it 9 months ago, and it was me, and the XDP was the choice mainly because :

A) It is more than powerful enough to run most anything pretty well
B) MS2 have proved that a lesser variant can work for the intended purpose
C) The TA board is ideal as a modular starting point
D) It's cheap enough and easy to get

Thanks for your input.

Fred.

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FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Thu Oct 02, 2008 8:20 pm
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Would there be any noticeable advantage over 16 bit?
Let's not forget what happened when MS1 went to MS2, we'll need more complex software to iron out all of the interference the new 32 bit CPU picks up due to its higher resolution. this will extend development time and costs.

We are currently using a chip that has X-Gate, which is a second, faster RISC co-processor making it a dual core CPU.

Once the base model is up and kicking, I'm sure the likes of Fred or Sean will find a way to get the X-Gate doing the super fast timing required for the ignition, injection and comms leaving more and more capacity in the S12 core for the complex stuff likely to be added as the project progresses.

So you have to ask yourself when considering 32 bit, Would the juice be worth the squeeze??

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Thu Oct 02, 2008 8:30 pm
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