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