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Topic: Making the Cortino (Read 3538 times) previous topic - next topic

westfw

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Assuming it is mainly clock-speed that is the complicating factor, how much faster than 16MHz could one safely run a microcontroller at, using simple double-sided PCB's, and a bit of care routing the PCB?

I don't think you can make that assumption.  "Maple" increased clock speed, increased board density (many more IOs than Arduino) and tried to increase A-D resolution, all at the same time.  A tough job.  And some chips are famous for being "noisier" than other chips, despite similar clock speeds.  Good show on the Maple team actually paying attention to such things; I don't know if other would-be "improvers" take the same care.

gbulmer

#16
Jun 20, 2010, 05:08 pm Last Edit: Jun 20, 2010, 05:56 pm by gbulmer Reason: 1
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And some chips are famous for being "noisier" than other chips, despite similar clock speeds.

Very interesting point. Thanks for the advice.

Might you suggest how I might discover this? My candidates are ST Micro STM32F and NXP LPC13xx or LPC17xx. I've been recommended SM32F by a very capable person, but he is using many-layer boards as his system is digital video (very high speeds).

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Good show on the Maple team actually paying attention to such things;
Yes a wonderful example. I am very impressed.

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I don't know if other would-be "improvers" take the same care.
I understand that I don't understand all of the difficulties, but I'd like to try to follow them. The Leaflabs Maple is an inspirational piece of work.

For some of the projects we'd like to try (like an onboard interpreter), it gets easier with single address-space, 32-bit machines and a good amount of RAM (64K+), though that won't be the first goal!

GB

Oh goodness, I have 668 posts, the next door neighbour of the beast  ;-)

ArduinoAndy

#17
Jun 21, 2010, 04:35 pm Last Edit: Jun 21, 2010, 04:36 pm by ArduinoAndy Reason: 1
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I was thinking of a single-sided arm board  then gave it up.


If you would have made a single sided ARM board it would have been a "first" and would have never worked
to spec.  8-) 8-) 8-)
"Never trust an Internet bully who insults and makes fun of your level of intelligence."

ArduinoAndy

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How so, the Batman has many years on many of us.  


What? WestFw was in diapers when I was designing printed circuit boards ;D ;D ;D
"Never trust an Internet bully who insults and makes fun of your level of intelligence."

westfw

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WestFw was in diapers when I was designing PCBS

Heh.  Not very likely :-(
However, while I have designed some PCBs, I make no claims to being an actual PCB designer, especially when it comes to high-speed boards.  Alas, I'm not alone.  There are far too many "products" where someone plunked down a circuit, got some autorouter to connect all the signals,  shipped the design off for near-automatic fabrication, and assumed it would just work...  Sometimes it does!  There are things I do with my board designs that I INTEND to help with high-speed behavior, and they seem to be more than other people do, but I don't have the "modify the design and actually measure the results" experience that it would take to actually have much confidence.  (like, there seem to be competing opinions about "ground planes" vs "single point GND returns"...  Sigh.)

pracas

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If you would have made a single sided ARM board it would have been a "first" and would have never worked to spec.


nay... i don't understand PCB design and component behavior so well... and thought of it as a possibility.. perhaps you can design one batman ;)
Be The Change...

westfw

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If you would have made a single sided ARM board it would have been a "first" and would have never worked to spec.

I designed a single-sided breakout board for the Luminary 3S10x series.   But those have only 28 pins and run at 20MHz, and I never actually built it so I don't know whether it actually worked.  The design phase itself was pretty "illuminating."  "In what way is a 28pin ARM chip different from a 28pin AVR chip?" (7 power supply pins and 4 "extra" jtag pins start the list...)

ArduinoAndy

12 BIT A/D - need I say more.  ;)
"Never trust an Internet bully who insults and makes fun of your level of intelligence."

westfw

Hmm.  Interesting points.  High-res A-D converters in MPUs are someone notorious, and I've seen references to all sorts of special mechanisms to get reasonable resolution out of them (like putting the rest of the CPU to sleep while the A-D does the conversion, IIRC.)  And I guess you'd have to start by actually implementing those separate power supplies...

westfw

Huh.  atXmega (which also has a 12bit A-D converter) in the 48-pin package has its analog power pins immediately adjacent to the crystal oscillator pins!  That's just so ... Grr.

gbulmer

I hadn't looked hard, but hadn't spotted that 'ingenious and innovate' positioning of the only guaranteed source of high-frequency noise, the crystal, w.r.t. the ADC inputs. A useful observation. Thank you.

I had noticed Atmel had changed the pin-out diagram from "you can see every pin function on one pin out diagram", which I really like, to just the name of the I/O register.
e.g. in doc8135, about the ATxmega128D4, ATxmega64D4, ATxmega32D4, ATxmega16D4 figure 2-1

I had felt the diagram change was a change for the worse because it made it harder to work with the chip. I wonder what other annoyances are masked by the bland port-only pin-out diagram?

Thank you.

westfw

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hadn't spotted that 'ingenious and innovate' positioning of the only guaranteed source of high-frequency noise, the crystal, w.r.t. the ADC inputs. A useful observation.

Not the ADC inputs, the AVCC power supply pin.  This feature seems to be maintained across all the packages, actually.  Maybe it makes sense; the crystal oscillator WOULD be considered analog electronics; perhaps it and some of the other more obviously analog circuitry legitimately share power supplies, and perhaps any oscillator-related noise is at frequencies far above anything relevant to the ADC anyway.  But...  It's not making me feel warm and fuzzy!


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