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5161  Forum 2005-2010 (read only) / Development / Re: Stellaris Luminary Developpement board on: January 08, 2009, 12:13:13 am
Linux generally take MUCH more RAM, and I don't think the Luminary parts have external ram.

For a low-cost board that IS capable of running linux, see the "Beagleboard" from digikey for $149:

ARM Cortex A8 running at 600MHz (1200 DMIPS)
2D/3D Graphics accelerator.
DSP
128MB RAM (2000 times as much as the Luminary.)
256MB Flash  (1000 times as much as the Luminary.)
USB-powered, about 3x3 inches.
http://beagleboard.org/

(Of course, for $149 you can also buy a old P3 or P4 system capable of running linux...)
5162  Forum 2005-2010 (read only) / Development / Re: Stellaris Luminary Developpement board on: January 06, 2009, 11:55:55 am
I've heard of it.  I have the older LM3S811-based eval board.

Luminary was the first vendor to offer ARM Cortex-M3 based chips, and is determinedly attacking the "microcontroller" space with their products, which go down to a $2 28-pin device.  They also deserve a certain amount of credit for the current crop of inexpensive high-function eval boards.  When they first appeared, all they offered were some expensive ($250) "development kits" that a lot of people thought were pretty overpriced for a vendor claiming to go after the lower end of the ARM market.

An ARM-uino would be interesting.  In particular, the current state of development tools for M3 is pretty confusing; it'd be really nice to have an all-in-one multi-platform suite like arduino that would get you started all at once.  But it would be difficult, too.  One vendor already has introduced an arduino-formfactor ARM board (based on STM32 rather than Luminary):
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1227128468
They got rather beaten up on software incompatibility issues...
5163  Forum 2005-2010 (read only) / Development / Re: Eagle Questions on: January 01, 2009, 11:45:28 pm
No rules of thumb that I know of.  For small boards, it is fast enough to start with components far apart in random orientation, route, move things around and try again, repeat.

The Eagle autorouter is not very highly respected...
5164  Forum 2005-2010 (read only) / Development / Re: Recommendation for Over Current on: December 30, 2008, 10:29:32 pm
The easy solution is to put something like a 74ac540 in between the pins and whatever you're driving.  74AC series has somewhat higher drive capability than the AVR, should be pretty inexpensive, and if you overload it to the breaking point, it's the cheap 74ac540 that dies and not your arduino...

Current limiting resistors are a good idea too; you ought to have some idea what the max current your "connected thing" will draw...
5165  Forum 2005-2010 (read only) / Development / Re: Should flux be cleaned from pre-assembled boards? on: November 15, 2008, 04:22:34 pm
I dunno.   "some flux" wouldn't bother me much.  I don't expect or require boards to be spotless (and actually having them conformally coated, which might be considered the next step up in professionalism, would definately be a BAD thing), but I don't expect them to be "messy", either.   It sounds like your boards have a LOT of flux; perhaps significantly more than I would leave behind if I soldered them myself.  Care to post a picture?
5166  Forum 2005-2010 (read only) / Development / Re: Should flux be cleaned from pre-assembled boards? on: November 15, 2008, 03:28:10 am
If it's "no clean" flux, I don't see why a vendor should be expected to remove it; it is rather greener to leave it on (no volatile solvents polluting anything.)  OTOH, I wouldn't there to be so much left that it's an eyesore, and I'm not sure how you as the customer can know whether or not it's a non-corrosive flux...  (although, it's the water-soluble fluxes that tend to be more corrosive...)
5167  Forum 2005-2010 (read only) / Development / Re: ATmega328P // 32k 28-pin dip on: March 11, 2008, 12:29:41 am
Heh.  I've never felt motivated to try to get samples out of Atmel, but it's nice to know that people who deserve them DO get them!
5168  Forum 2005-2010 (read only) / Development / Re: ATmega328P // 32k 28-pin dip on: October 25, 2007, 05:59:24 pm
The P-suffix "picopower" feature set is described somewhat here: http://www.atmel.com/products/avr/picopower/Default.asp

Quoting:
Quote
The key elements are:
- True 1.8V Supply Voltage
- Minimized Leakage Current
- Sleeping BOD
- Ultra Low Power 32 kHz Crystal Oscillator
- Digital Input Disable Registers
- Power Reduction Register
- Clock Gating
- Flash Sampling

I should note that the Arduino core firmware is not currently set up to utilize even the more primitive power saving modes available on the current AVR cpus, so the "picopower" aspects are not likely to be so interesting as the doubling of flash, ram, and eeprom...

None of the 28-pin picopower AVRs are showing up at (digikey, mouser, etc) and the atmel page says "by the end of 2007", so I suspect Limor's "sometime in 2008" is a good estimate, unless you're a major player...


5169  Forum 2005-2010 (read only) / Development / Re: Eagle Soldermask / Silkscreen Problem on: November 25, 2008, 01:18:12 am
Many (some?) PCB vendors automatically apply the soldermask to ALL the layers, including the silkscreen, just so that vias and pads don't end up covered when they shouldn't be.  Check with seedstudio...

Otherwise, modify the library.  I'm not sure it's a good idea to have silkscreen under flat SMT components anyway...
5170  Forum 2005-2010 (read only) / Development / Re: Easy way to increase the PWM outputs? on: November 17, 2008, 12:53:24 pm
You can do multiplexing with PWM outputs driving the individual LEDs, but it might be a bit tricky.  Ideally, you want the multiplex frequency to be much lower than the PWM frequency.
5171  Forum 2005-2010 (read only) / Development / Re: Max Clock Speed of Arduino on: November 13, 2008, 04:07:59 am
The AVR microcontroller used has a max specified speed of 20MHz at 5V, and somewhat less at the voltage goes down.
That's the specification.  You MIGHT be successful running at a higher clock speed...
you will have to go to some effort to get the arduino software to work correctly at speeds other than 8 or 16MHz...
5172  Forum 2005-2010 (read only) / Development / Re: Cost of an Arduino Board for a poor student on: October 29, 2008, 07:56:58 pm
BTW, using an lm317 to get 3.3V from 5V is pretty marginal.  Looking at the datasheet, the dropout voltage is about 1.75V at 0C, decreasing slightly as temperature increases.  Since 3.3V = 5V - 1.7V, it's right on the edge of being able to maintain regulation...
5173  Forum 2005-2010 (read only) / Development / Re: Cost of an Arduino Board for a poor student on: October 29, 2008, 11:15:31 am
Well, most of your prices are MUCH better than I can get at any "local" electronics stores in the US, even the "surplus" dealers.  You should count yourself VERY lucky to have such a great store near you, and I suspect that you're being VERY optimistic if you think someone in "any country in the world" can get parts at similar prices...  (even the ATmega8s on eBay are about $2 each...)

Quote
76 rounded pins females for sockets  1.10
What are these?  They sound too cheap to be socket pins, and there wouldn't be 76 of those on an arduino anyway...
5174  Forum 2005-2010 (read only) / Development / Re: Cost of an Arduino Board for a poor student on: October 10, 2008, 10:07:17 am
Quote
This shops usually need a lot of time to sell a new version of any micro, and they keep big stocks, so unfortunatly here is still easier to find a 12C508 than a 12F508.
This is relatively common in the US, for shops (including mail order) that cater mostly to hobbyists.  The big difference (which is relatively recent) seems to be that some of the major "professional" electronics distributors have decided that they are willing to sell relatively small orders to individuals as well (Digikey, mouser, newark).  Even some of the manufacturers now sell direct to anyone (freescale, microchip.)   On the one hand, this is not good for the small electronics dealers, and perhaps that's why it's difficult to find a local store with ANY "parts."  On the other hand, it's pretty nice from the perspective of being able to buy the latest chips.
5175  Forum 2005-2010 (read only) / Development / Re: Cost of an Arduino Board for a poor student on: October 09, 2008, 07:09:54 pm
Back in about 2004, Atmel announced that the tiny11 was going to be sold for $0.25 "in any quantity."  Now, "in any quantity" when a manufacturer says it doesn't quite mean "Q 1 from digikey", but one of the PICList members was able to organize a group buy of about 600 chips (at $0.25 each), distributed to PICList members in sets of 50 or more.  There was a flurry of development tool discussion, much of which  you can find referenced here: http://www.geocities.com/westfw/electronics/attiny11-prog-notes.html (you should like the PCB design :-))

Prices at digikey never got lower than about $0.32 for 100q, and I think $0.54 each for one at a time.  Still a pretty good price.

Tiny11 End-of-life was announced by Atmel in 2007.  All things considered, it was an ugly little example of an AVR (no RAM, no calibrated oscillator, funny programming, etc, etc), and I'm not sorry to see it go.  But it is sorta sad that nothing has replaced it at that price point.

Using US digikey prices as a reference (perhaps different elsewhere, of course), it looks like the cheapest CPU out there at the moment is the freescale MC9RS08KA1 at $0.78 each (0.43 in 100q)  (The RS08 micros seem to be pretty nice; I looked at them a couple years ago in conjunction with one of the freescale contests.  But they don't have a lot of support in the hobbyist community, as far as I can tell.)  I don't think I've ever bought a microcontroller at a "shop", but I'd expect to pay much more at anyplace with a retail storefront.  "Radio shack", which is probably the closest the US comes to a chain consumer electronics store with SOME parts, would surely not sell such a thing for less than $2...

Note that (also in the US),  PIC microcontrollers have recently had the interesting development that flash parts have passed OTP parts WRT low cost; a 12F508 is significantly cheaper than a 12C508.
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