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5641  Using Arduino / Displays / Re: E-Ink ED060SC7 (Kindle Display) on: May 10, 2012, 09:25:25 am
Looks like the "SPI" interface is for the onboard FLASH memory.  (See Note 5-1)  The main interface seems to be 8-bit parallel.

If you can get a (somewhat) working Kindle and an oscilloscope it shouldn't be to hard to figure out what is going on.
5642  Using Arduino / Project Guidance / Re: LineBot on: May 10, 2012, 09:12:12 am
> Q1: what are fly-back diodes, what's their purpose and what values should I use(Are 1N4004 or 1N4001 useful?)

When you have current running through a inductor (coil of wire like a motor winding or solenoid) it forma a magnetic field: turns the coil into an electromagnet.  When you disconnect the flow of current the magnetic field collapses rapidly.  As it collapses the change in magnetic field through the coil induces an electrical current opposite the original current.  This can cause a large reverse-current spike.  The flyback diodes short out this reverse current spike to prevent it from damaging other semiconductors in the circuit.
5643  Using Arduino / Microcontrollers / Re: Attiny85 programming failing - Invalid device signature on: May 10, 2012, 08:49:57 am
If you turn on verbose output you will get to see the value of the received signature.  If it matches the ATmega328P then you are accidentally resetting the UNO.  If it is all 0's or all FF's you have an incorrect connection on the target processor.
5644  Using Arduino / LEDs and Multiplexing / Re: Multiple LED patterns independently on: May 10, 2012, 08:22:12 am
You could use some shift registers to get more output pins and run everything from one Arduino or you could use one Arduino for each set of lights.  Which you choose depends a lot on your skill set.
5645  Community / Gigs and Collaborations / Re: Looking for some help with program encoder on: May 09, 2012, 10:34:11 pm
I think you can run the SPI interface at 4 MHz.  You would need to do two 8-bit 'transfers' to get 13 bits of data but I think that might work.

I think you'll need some RS422A drivers/receivers to translate the signals to something the Arduino can accept.
5646  Using Arduino / Microcontrollers / Re: output speed fluctuation on: May 09, 2012, 10:21:21 pm
No, the Arduino will not slow down the system clock speed (16 MHz) when the chip gets hot.  There is a ceramic resonator (on earlier models: a crystal) to regulate the frequency to very close to 16 MHz.  If the ATmega processor temperature exceeds the specified temperature limits the operation will become unreliable.
5647  Using Arduino / LEDs and Multiplexing / Re: Multiple LED patterns independently on: May 09, 2012, 10:16:22 pm
You're not the first to ask.  That's why I wrote this sketch I call DaftPunkLights:
Code:

const int CheekPins[] = {
  3,4,5,6,7,8,9,8,7,6,5,4};  // gives forward and back
const int CHEEK_COUNT = sizeof CheekPins / sizeof (int);
const int CheekIntervals[] =
{
  300, 300, 300, 300, 300, 300,
  300, 300, 300, 300, 300, 300}
;  // Milliseconds
unsigned long CheekTime = millis();
int CheekStep = 0;

const int ChinPins[] = {
  10,11,12,13};
const int CHIN_COUNT = sizeof ChinPins / sizeof (int);
const int ChinIntervals[] = {
  300, 300, 300, 300}
;  // Milliseconds
unsigned long ChinTime = millis();
int ChinStep = 0;

void setup()
{
  int i;
  /* Cheek LED's */
  for (i=0; i< CHEEK_COUNT; i++)
    pinMode(CheekPins[i], OUTPUT);  // Yes, it's OK to set the pinMode twice on some pins

  /* Chin LED's */
  for (i=0; i< CHIN_COUNT; i++)
    pinMode(ChinPins[i], OUTPUT);
}

void loop()
{
  // Do the cheek animation
  if ((millis() - CheekTime) > CheekIntervals[CheekStep])
  {
    CheekTime = millis();
    digitalWrite(CheekPins[CheekStep], LOW);
    CheekStep = (CheekStep+1) % CHEEK_COUNT;
    digitalWrite(CheekPins[CheekStep], HIGH);
  }

  // Do the chin animation
  if ((millis() - ChinTime) > ChinIntervals[ChinStep])
  {
    ChinTime = millis();
    digitalWrite(ChinPins[ChinStep], LOW);
    ChinStep = (ChinStep+1) % CHIN_COUNT;
    digitalWrite(ChinPins[ChinStep], HIGH);
  }
}
5648  Using Arduino / Project Guidance / Re: Best power saving mode for Arduino UNO? on: May 09, 2012, 10:14:06 pm
> Question 1: There are other sleep modes, but what do they do?
Read the ATmega328P datasheet for information about the sleep modes.

> Question 2:  What is twi and spi? Is there anything else I can disable (e.g. BOD) and how do I do it?
They are serial communication interfaces often used to communicate with peripheral devices such as Ethernet, SD card, RealTime Clock...

> Question 3: Is there a power saving technique (code) that doesn't halt the program on the Arduino?
I believe the sleep modes all stop the processor clock.
5649  Using Arduino / Programming Questions / Re: How do i use the Sparkfun Touch Shield to control pin 6 on the Arduino? on: May 09, 2012, 09:54:52 pm
Did you remember pinMode(6, OUTPUT) in setup()?
5650  Using Arduino / Networking, Protocols, and Devices / Re: Ethernet client connect failure on: May 09, 2012, 09:51:23 pm
There is a reported (compiler?) error in the reading of 16-bit socket registers.  It's reportedly fixed in the upcoming 1.0.1.

See: http://code.google.com/p/arduino/issues/detail?id=605

You can insert the fix at line 253 of w5100.h
5651  Using Arduino / General Electronics / Re: help on dual dc supply on: May 09, 2012, 11:51:54 am
One full-wave rectifier per power supply so you need two.
5652  Using Arduino / Programming Questions / Re: ATtint24 Core Library for Arduino on: May 09, 2012, 11:49:55 am
Are you sure its running at 0.8 MHz and not 1 MHz?   Sounds like you forgot to "Burn Bootloader" to set the fuses and the factory default 1 MHz fuses are still in effect.
5653  Using Arduino / Sensors / Re: Accelerometer Problems - MMA7361L not getting any real data from the device. on: May 09, 2012, 11:41:05 am
Have you tried a HIGH signal on the SLeeP pin to make sure the device is out of SLEEP mode?
5654  Using Arduino / Displays / Re: Help with old-school display on: May 09, 2012, 10:53:30 am
That looks like it may be a Vacuum Fluorescent Display (VFD).  I don't think you can drive one directly with an Arduino since they require high voltages but I expect there are driver chips that will allow the Arduino to control one.

Of course if it is just a blue LED display then the Arduino can drive it directly.
5655  Using Arduino / General Electronics / Re: help on dual dc supply on: May 09, 2012, 10:47:44 am
Yes, two 12V transformers can be wired to act as a center-tapped 24V transformer.

Full-wave rectifiers will produce lower ripple than half-wave rectifiers.

You'll need +12V and -12V regulators (if you want regulated voltage) and filter capacitors.
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