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4921  Forum 2005-2010 (read only) / Development / Re: Arduino compatible with lots of IO? on: December 28, 2009, 03:05:39 am
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According to the instruction set manual the SBIS / SBIC timing will be different.
I'm still not seeing it.  Can you point me to page and section/line numbers or something?

Both the 1280 and 168 datasheet say that SBIS executes in 1, 2 or 3 cycles, and the avr instruction reference says this is for for the don't skip case, skip single-word instruction, and skip double-word instruction cases.  A double-word instruction would be something like LDS, containing a full 16bit address, not something dependent on memory size.
4922  Forum 2005-2010 (read only) / Development / Re: Arduino compatible with lots of IO? on: December 27, 2009, 04:29:14 pm
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This in turn implies that [AVRs with more than 64k of flash] have slightly different timing for some instructions (e.g. SBIC, SBIS).
Does it?  I didn't see anything in the datasheet that says that.  However, IO registers for your extra IO ports are likely to be beyond the range of ports that SBIS/SBIC can operate on, regardless of the amount of memory, reducing you to LDS/SBRC (2 cycles slower and uses a register.)

There is the RAMP banking registers for accessing RAM or Flash in devices with more than 64k, but that won't affect IO register access on the 1280 since there is far less than 64k of "data" space (The 128k of FLASH is in a separate address space.)
4923  Forum 2005-2010 (read only) / Development / Re: TVBGone - Arduino Schematic - Correct? on: December 27, 2009, 01:17:44 am
Much nicer (version 2.)  Not my favorite style of schematic (aside from power, I like to actually see wires), but it is pretty common and not something I can complain about.  Nicely named and labeled signals...

LED2 is backward.

R1 (with the IR LED) is too big (1k); you probably want larger resistors with the status/power LEDs (since they're just status) and a lower value on the IR led since that's where you want to send most of your power...

Use thicker traces on the PCB, especially if you're going to make it yourself.   See http://www.instructables.com/id/Make-hobbyist-PCBs-with-professional-CAD-tools-by-/

You can probably make this into a single-sided board with some effort.
4924  Forum 2005-2010 (read only) / Development / Re: TVBGone - Arduino Schematic - Correct? on: December 26, 2009, 08:04:02 pm
C1/R1/LED2 is almost certainly wrong.
D1 should have a current-limiting resistor.

The schematics is ugly and hard to read; it's bad form to run signals inside of component outlines.  Put a nice horizontal +5 line across the top and GND at the bottom and run appropriate signals vertically (or use GND and V+ symbols.)
4925  Forum 2005-2010 (read only) / Development / Re: Name on: December 26, 2009, 08:15:46 pm
I'd keep xxxDUINO for boards that are both logically and conceptually nearly entirely similar to Arduino.  If you add significant functionality (ie for robotics) you might as well pick an entirely new name.  For example, Freeduino and BoArduino are intentional and exact clones (more or les) of Arduino, while http://www.evilmadscientist.com/ has several projects that are compatible with the Arduino environment and bare names with no "ino" in them anywhere (Peggy2, Bulbdial, Meggy Jr...)

On the other hand, adding that -uino suffix does a nice job of instantly conveying an attempt at arduino compatibility, and aids web searchiblity. (Who named "Processing" and "Wiring" ?!  HORRIBLE names to try to search for info.  "Arduino" works MUCH better, and a non-word that isn't even Italian is probably better...)
4926  Forum 2005-2010 (read only) / Development / Re: Eagle help - rotating parts on: December 11, 2009, 11:35:59 am
Lots of the drop-down (pop-up?) boxes can be typed in (drill size, track width, etc.)

4927  Forum 2005-2010 (read only) / Development / Re: Eagle help - rotating parts on: December 11, 2009, 05:31:00 am
Did you find the "rotate" icon in your tools?  horizontal shaded bar, vertical black bar, circular arrow?  When you click that, by default the rotation angle is set to 90 degrees, but a field
"Angle" appears in the top menu bar and you can change the angle to an arbitrary number.

You can also use a typed command in the command window, like "rotate R10" (rotate 10 degrees) or "rotate =R10" (rotate to 10 degree absolute angle.)  Typed commands can be very useful for more exacting actions...
4928  Forum 2005-2010 (read only) / Development / Re: wide range power regulation methods? on: December 04, 2009, 01:34:57 pm
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All of the suggestions but one cap out at about 35V
Note that LM317 based designs do not need to be connected to absolute "ground", so you can (theoretically) stick in a 317-based pre-regulator that drops a 50V input voltage by 20V to get it within range of other "normal" circuits.  Automatically switching it in/out would be a challang, though...

National's "webbench" says there are about 20 different switching regulator chips that will handle the requirement (8-50V in, 3.3V@300mA out), though I didn't delve into details.  The LM2591HV looked promising.  Up to 60V input.  Note that there's a BIG market for 48V nominal input (usually 36-72) DC-DC converters for the telco markets, though they tend to be aimed at higher output currents. http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=13065 for example.   (however, NOT cheap if you have to buy them new...)

I assume that a 12S lipo user is unlikely to be concerned that the voltage regulator costs $3 rather than $1...  :-)
4929  Forum 2005-2010 (read only) / Development / Re: wide range power regulation methods? on: December 04, 2009, 03:30:10 am
In the end, the zener/transistor pre-regulator scheme will need the same total size of heatsink as a plain linear regulator chip, though it might be easier to find a power transistor with the appropriate power dissipation characteristics.

Still, real switching regulators are a good thing to look at for power supplies that you want to handle high differences of input and output voltages.  And they've gotten rather cheap.  The (very common) MC34063A runs about $0.30 from digikey and claims to handle an input voltage of up to 40V.  This is the chip used in most of the automotive "cell phone" power supplies, so it's pretty easy to find a sample circuit to test to destruction.  I don't know how difficult it is to make it into a complete supply with a very wide input range; a few moments with one of the online regulator calculators might be useful.

Most LM317 datasheets include a sample circuit for a switching regulator, and another for a "tracking pre-regulator", but I don't think I've seen them combined.  And the circuit tends to use large inductors and low freqencies (by today's standards.)
4930  Forum 2005-2010 (read only) / Development / Re: wide range power regulation methods? on: December 03, 2009, 07:52:59 pm
BenF: your circuit
 
is NOT a "switching regulator"; it's a traditional zener/transistor linear regulator and has all the power dissipation problems of any other linear regulator.  See http://en.wikipedia.org/wiki/Linear_regulator, the section labeled "Simple Series Regulator."

A switching regulator needs some sort of energy storage device (inductor or capacitor) to store energy, which is then switched from input to output by the control circuit.


4931  Forum 2005-2010 (read only) / Development / Re: smallest arduino board? on: June 02, 2009, 10:05:29 pm
Nice pictures.  I mean, not breathtakingly beautiful, but plenty good enough to show how things are set up, in ways that weren't obvious on the lesser closeups...  Useful!  Good work.

4932  Forum 2005-2010 (read only) / Development / Re: smallest arduino board? on: May 28, 2009, 02:25:41 am
I rather like the idea of using a WW socket and putting components on the board UNDER the socket as well as using the socket pins themselves for plugging into the next "layer" of circuitry.
4933  Forum 2005-2010 (read only) / Development / Re: smallest arduino board? on: April 17, 2009, 08:46:55 pm
Still using the internal oscillator, though?
4934  Forum 2005-2010 (read only) / Development / Re: smallest arduino board? on: April 14, 2009, 03:28:12 pm
I've been playing with this design for a RRBBB, but it's clear I have slightly different goals (I was less interested in breadboards and more in "runtime board" like functionality with pads to attach to.  And I was less worried about the (relatively large) SMT components on the bottom, or being able to "easily" attach a programming cable.)
http://lh3.ggpht.com/_NOmmtpdLD5M/SeTwlLO-MvI/AAAAAAAACeo/Qhf-Lote4bs/RRBBB.png
4935  Forum 2005-2010 (read only) / Development / Re: Extreme bare bones Arduino - whats needed? on: November 11, 2009, 11:27:08 pm
At the very least, I think you can get by with no parts other than the power supply.  This requires re-configuring the RESET pin and clock source via the fuses, and will require that you have a programmer than can still program the chip even when reset is disabled (I think this requires a "high" voltage on the Reset pin, so a simple parallel port programmer may not be sufficient.)

At this point, though, you're not very Arduino-compatible.  You might as well hang out on AVR-freaks.net instead.  :-)

The minimum arduino-compatible system is probably a resistor from reset to Vcc, if you reprogram the fuses to run the internal clock and declare it as an 8-MHz lillypad...
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