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10516  Using Arduino / LEDs and Multiplexing / Re: cheapest place to get 500 or so LED's on: May 17, 2011, 11:42:00 am
There ought to be a cheap way to turn a clear LED into a diffuse one?  Dip in the right kind of glue and then into icing sugar perhaps? 

Several ways I'm sure. Emery cloth, sandpaper, etc. However with 125 leds it would become a real chore and trying to make them identical might be a challenge. Diffused leds don't cost more, and they are best choise for led cubes in my opinion and experiance having built a 5x5x5 blue led cube.

10517  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 17, 2011, 09:31:06 am
What lefty is suggesting is (I think) exactly what I have on my two current 1284 designs.

Note the diode on the FTDI chip's RXD line. I'm not 100% sure that's needed but I've had trouble before with this sort of setup where the active chip powered the inactive chip through the IO pin. This is easy to get around by tristating the active chip's output as well but I prefer a hardware option that doesn't require a use to know about this stuff.

This should allow the USB chip to only be powered when USB is available.

@crossroads, this is a board designed for my network and it's pretty specific to that. I won't be competition, not yet anyway smiley


The method the standard arduino uses with 1K resistors in series with the rec & tx pins works pretty well.

10518  Using Arduino / Installation & Troubleshooting / Re: AVR Dragon on: May 16, 2011, 10:18:34 pm
Any modifications should be done on the Arduino sketch program?

Nothing would change or be required inside any specifc sketch. The arduino IDE files would need to be modified/configured to utilize the Dragon programmer. AVRDUDE, the program that the IDE uses to do uploading already knows how to talk to a Dragon as shown in the AVRDUDE.conf file:

# AVR Dragon in ISP mode
  id    = "dragon_isp";
  desc  = "Atmel AVR Dragon in ISP mode";
  baudrate = 115200;
  type  = dragon_isp;

So it's a matter of defining your specific new board type in the IDE core boards.txt file and tell it that the new board uses the dragon to perform the upload. Can't give you specific step by step instructions as I don't own a dragon and have never tried to modifiy the IDE to use it. I just know it should be pretty straight forward.


10519  Using Arduino / Programming Questions / Re: servo motor turning degrees on: May 16, 2011, 10:00:59 pm
that makes the servo motor rotate from 0 to 180 degrees only twice and then stop.

Could you be more clear. Do you mean do the following:

1. Move from 0 to 180 degress (how fast to move, fastest possible or at some slower rate?)
2. pause for some time ?
3. move from 180 to 0 degrees
4. pause for some time ?
5. move again from 0 to 180 degress
6. pause for some time
7. Move again from 180 to 0 degress
8. Stop all processing until ?

That is may or may not be what you want to do, but that is the details needed to actually code whatever sequence you want to perform.

10520  Using Arduino / Programming Questions / Re: Why does Arduino tend to use such low baud rates in tutorials? on: May 16, 2011, 09:52:07 pm
Is there any general reason to use lower baud rates (disregarding the case where you need to interface with a device that doesn't support higher rates)?

No, not if the device can handle the rate. Keep in mind that the highest baud rate puts a burden on speed of processing receive data for the arduino. the serial receive buffer is 128 bytes in size and if ones loop sketch is too slow it's possible to drop characters if lots of data is coming in at the highest possible baud rate. So while the highest baud rate can help your sketch run faster on the transmit side, it brings a burden on processing the receive data stream at the same time. It's really application dependent, no one size fits all cases.

10521  Using Arduino / Installation & Troubleshooting / Re: Arduino Uno Communications Problem Solved on: May 16, 2011, 09:42:29 pm
Hope this helps someone. This is supposed to be fun after all right! - Kevin 

I'm glad you figured it out and shared your solution, I'm sure it will help someone one someday.

10522  Using Arduino / Programming Questions / Re: Why does Arduino tend to use such low baud rates in tutorials? on: May 16, 2011, 09:38:38 pm
Anybody know why the defaults are set so low?

There is no specific default. Bootloader baudrate has changed over time but that has no relationship over what specific baudrate various authors used in their sketch examples. I tend to use 57600 baud in most of my projects.

10523  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 16, 2011, 06:03:20 pm
Lefty, i don't follow... It seems like you are saying that a jumper needs to be moved to switch from wall wart to USB power. Or does your jumper switch from auto-switching to not auto-switching?

I proposed eliminating the auto-voltage switching logic altogether. Instead replace with a simple 3 pin SIP male pin header and a two position jumper clip. In one position the boards power is coming from the on-board +5VDC regulator, in the other jumper position the boards power comes from the USB +5vdc source. You decide how you want to power the board and place the jumper appropriately. A two position manual switch could also work just as simple as it does in the Seeeduino board designs. How the board is powered has no bearing on if you are using the usb serial function or not, if the board has power the usb can function period.

Edit: What I proposed is to go back to the design that arduino used with the  Diecimila board.

Schematic:  Note the power selection jumper in the lower left hand of the drawing.

10524  Using Arduino / Programming Questions / Re: Analogue to digital conversion for volume control on: May 16, 2011, 05:52:37 pm
Pretty poor picture. But I would guess that you have the pot wired wrong. Usually the variable resistance is the middle terminal, not one of the end terminals.

10525  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 16, 2011, 05:28:55 pm
I find it mildly convenient to be able to take my computer over to my running project, hook up my USB cable, upload new code, then disconnect shortly thereafter without the project having to reboot. Would your solution allow that?

Yes, that would still function as you stated.

As far as power switching, the arduino auto-voltage switching remains powered by the external source if power is on both usb and the external power connector at the same time (external has priority), so that would have no bearing on what you are asking to do, the board would not reboot because you removed the usb connector.

10526  Using Arduino / Project Guidance / Re: Changing the clock frequency of an Arduino Mega 2560 on: May 16, 2011, 05:23:37 pm
Well in theory it might work. The bootloader would have to be recompiled to work at the new frequency, something not able to be done inside the arduino IDE. A new board entry for the boards.txt file defining this new configuration is needed, but that is simple. Not sure how accurate the millis(), micros(), and delay() functions would be with your new frequency, so that would have to be looked into. But the hardware side is just a simple swap out and adding the padding caps, however smd desoldering/soldering in not for the inexperienced.


10527  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 16, 2011, 05:07:30 pm
If the device is going to live somewhere away from a PC ou need to power it, but for the occasional trip to the PC to be updated or whatever it comes in very handy not to have to go searching for the wall art.

What I proposed doesn't prevent that, it just requires moving a jumper clip from one position to the next position. What's not handy about that?

Another example of the auto-voltage lameness. Assume your project is powered externally and is independent to a PC. Why power up the FTDI or 8u2 chip? Check out the Seeeduino design for power selection, manual two position switch for usb/external power and FTDI power source is hardwired to the USB connector only. That's good functional design.

10528  Using Arduino / Project Guidance / Re: Powering Arduino with 12V, 7.5Amp - doable? on: May 16, 2011, 05:00:58 pm
I would still not run 7.5 amps through the arduino ground pin(s) to the high current load. Better to have separate properly sized +12 and ground wires to the high current load and then just a separate +12v and ground to the arduino external power connector.
10529  Community / Bar Sport / Re: Rant - Destroying an Arduino EEprom on: May 16, 2011, 03:33:45 pm
I would just call it an example of digital masturbation.

10530  Using Arduino / Programming Questions / Re: Continuous Rotation Servo + PIR Sensor Help! on: May 16, 2011, 03:28:35 pm
On the library i can only find rotation codes for non continuous servos (e.g codes that rotate the servo a fixed amount of degrees either to the left or right) and so forth, could someone direct me to a library concerning continuous rotation servos?

Same library is used, same signal to the servo. However while a normal servo rotates and stops given a signal from 0 (degrees) to 180 ( degrees). The same commands going to a modified servo would result in  0 = full speed in one direction, 180 = full speed on the opposite direction, and 90 = stop. Values sent between 0-89 or 91-180 would result in continous rotatation at a specific speed. Note that the 90 degrees = stop may have to be tweeked to find the specific stop condition for your specific servo due to calibration variation between servos.

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