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/*
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  Digital Pot Control
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  This example controls an Analog Devices AD5206 digital potentiometer.
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  The AD5206 has 6 potentiometer channels. Each channel's pins are labeled
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  A - connect this to voltage
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  W - this is the pot's wiper, which changes when you set it
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  B - connect this to ground.
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 The AD5206 is SPI-compatible,and to command it, you send two bytes, 
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 one with the channel number (0 - 5) and one with the resistance value for the
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 channel (0 - 255).  
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 The circuit:
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  * All A pins  of AD5206 connected to +5V
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  * All B pins of AD5206 connected to ground
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  * An LED and a 220-ohm resisor in series connected from each W pin to ground
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  * CS - to digital pin 10  (SS pin)
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  * SDI - to digital pin 11 (MOSI pin)
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  * CLK - to digital pin 13 (SCK pin)
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 created 10 Aug 2010 
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 by Tom Igoe
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 Thanks to Heather Dewey-Hagborg for the original tutorial, 2005
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*/
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// inslude the SPI library:
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#include <SPI.h>
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// set pin 10 as the slave select for the digital pot:
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const int slaveSelectPin = 10;
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void setup() {
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  // set the slaveSelectPin as an output:
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  pinMode (slaveSelectPin, OUTPUT);
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  // initialize SPI:
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  SPI.begin(); 
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}
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void loop() {
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  // go through the six channels of the digital pot:
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  for (int channel = 0; channel < 6; channel++) { 
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    // change the resistance on this channel from min to max:
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    for (int level = 0; level < 255; level++) {
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      digitalPotWrite(channel, level);
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      delay(10);
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    }
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    // wait a second at the top:
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    delay(100);
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    // change the resistance on this channel from max to min:
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    for (int level = 0; level < 255; level++) {
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      digitalPotWrite(channel, 255 - level);
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      delay(10);
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    }
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  }
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}
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int digitalPotWrite(int address, int value) {
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  // take the SS pin low to select the chip:
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  digitalWrite(slaveSelectPin,LOW);
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  //  send in the address and value via SPI:
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  SPI.transfer(address);
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  SPI.transfer(value);
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  // take the SS pin high to de-select the chip:
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  digitalWrite(slaveSelectPin,HIGH); 
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}