IO: Unify ADC examples

java/libraries/io/examples/AnalogDigital_SPI_MCP3001/AnalogDigital_SPI_MCP3001.pde

@@ -9,5 +9,12 @@ void setup() {
 }
 
 void draw() {
-  background(adc.getAnalog() * 255);
+  // this will return a number between 0 and 1
+  float measured = adc.analogRead();
+
+  // multiply with the supply voltage to get an absolute value
+  float volts = 3.3 * measured;
+  println("Analog Input is " + volts + "V");
+
+  background(measured * 255);
 }

java/libraries/io/examples/AnalogDigital_SPI_MCP3001/MCP3001.pde

@@ -10,7 +10,8 @@ class MCP3001 extends SPI {
     settings(500000, SPI.MSBFIRST, SPI.MODE0);
   }
 
-  float getAnalog() {
+  // returns a number between 0.0 and 1.0
+  float analogRead() {
     // dummy write, actual values don't matter
     byte[] out = { 0, 0 };
     byte[] in = transfer(out);

java/libraries/io/examples/AnalogDigital_SPI_MCP3008/AnalogDigital_SPI_MCP3008.pde

@@ -9,7 +9,14 @@ void setup() {
 }
 
 void draw() {
-  background(adc.getAnalog(0) * 255);
-  fill(adc.getAnalog(1) * 255);
+  // this will return a number between 0 and 1
+  float measured = adc.analogRead(0);
+
+  // multiply with the supply voltage to get an absolute value
+  float volts = 3.3 * measured;
+  println("Analog Input 0 is " + volts + "V");
+
+  background(255);
+  fill(measured * 255);
   ellipse(width/2, height/2, width * 0.75, width * 0.75);
 }

java/libraries/io/examples/AnalogDigital_SPI_MCP3008/MCP3008.pde

@@ -11,7 +11,8 @@ class MCP3008 extends SPI {
     settings(500000, SPI.MSBFIRST, SPI.MODE0);
   }
 
-  float getAnalog(int channel) {
+  // returns a number between 0.0 and 1.0
+  float analogRead(int channel) {
     if (channel < 0 ||  7 < channel) {
       System.err.println("The channel needs to be from 0 to 7");
       throw new IllegalArgumentException("Unexpected channel");