IO: Add an 8-channel ADC example using the MCP3008

java/libraries/io/examples/SPIAnalogDigitalOOP8/MCP3008.pde

@@ -0,0 +1,27 @@
+import processing.io.SPI;
+
+// MCP3008 is a Analog-to-Digital converter using SPI
+// other than the MCP3001, this has 8 input channels
+// datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/21295d.pdf
+
+class MCP3008 extends SPI {
+
+  MCP3008(String dev) {
+    super(dev);
+    super.settings(500000, SPI.MSBFIRST, SPI.MODE0);
+  }
+
+  float getAnalog(int channel) {
+    if (channel < 0 ||  7 < channel) {
+      System.err.println("The channel needs to be from 0 to 7");
+      throw new IllegalArgumentException("Unexpected channel");
+    }
+    byte[] out = { 0, 0, 0 };
+    // encode the channel number in the first byte
+    out[0] = (byte)(0x18 | channel);
+    byte[] in = super.transfer(out);
+    int val = ((in[1] & 0x03) << 8) | (in[2] & 0xff);
+    // val is between 0 and 1023
+    return val/1023.0;
+  }
+}

java/libraries/io/examples/SPIAnalogDigitalOOP8/SPIAnalogDigitalOOP8.pde

@@ -0,0 +1,15 @@
+import processing.io.*;
+MCP3008 adc;
+
+// see setup.png in the sketch folder for wiring details
+
+void setup() {
+  //printArray(SPI.list());
+  adc = new MCP3008(SPI.list()[0]);
+}
+
+void draw() {
+  background(adc.getAnalog(0) * 255);
+  fill(adc.getAnalog(1) * 255);
+  ellipse(width/2, height/2, width * 0.75, width * 0.75);
+}