IO: Add ADS1X15 Analog-to-Digital converter example

java/libraries/io/examples/AnalogDigital_I2C_ADS1X15/ADS1X15.pde

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+import processing.io.I2C;
+
+// ADS1015 and ADS1115 are Analog-to-Digital converters using I2C
+// they have four channels and 12 and 16 bits of resolution respectively
+// datasheets: http://www.ti.com/lit/ds/symlink/ads1015.pdf
+//             http://www.ti.com/lit/ds/symlink/ads1115.pdf
+
+class ADS1015 extends ADS1X15 {
+  ADS1015(String dev, int address) {
+    super(dev, address);
+    bitShift = 4;
+    conversionDelay = 1;
+  }
+
+  // returns a number between -1.0 and 1.0
+  float analogRead(int channel) {
+    return readSingleEnded(channel) / 2047.0;
+  }
+}
+
+class ADS1115 extends ADS1X15 {
+  ADS1115(String dev, int address) {
+    super(dev, address);
+    bitShift = 0;
+    conversionDelay = 8;
+  }
+
+  // returns a number between -1.0 and 1.0
+  float analogRead(int channel) {
+    return readSingleEnded(channel) / 32767.0;
+  }
+}
+
+
+class ADS1X15 extends I2C {
+  int address;
+  int bitShift;         // bits to shift the result to the right
+  int conversionDelay;  // in ms
+  int channel;          // last channel used
+  int range;            // see below
+
+  // possible voltage ranges
+  static final int INTERNAL_6V144 = 0;  // +/- 6.144V
+  static final int INTERNAL_4V096 = 1;  // +/- 4.096V (library default)
+  static final int INTERNAL_2V048 = 2;  // +/- 2.048V
+  static final int INTERNAL_1V024 = 3;  // +/- 1.024V
+  static final int INTERNAL_0V512 = 4;  // +/- 0.512V
+  static final int INTERNAL_0V256 = 5;  // +/- 0.256V
+
+  ADS1X15(String dev, int address) {
+    super(dev);
+    this.address = address;
+    this.channel = -1;
+    this.range = INTERNAL_4V096;
+  }
+
+  // be careful not to make the input voltage exceed VCC + 0.3V
+  // this is regardless of the selected input range
+  void analogReference(int type) {
+    if (type < 0 || 7 < type) {
+      throw new RuntimeException("Invalid range setting");
+    }
+    range = type;
+  }
+
+  int readSingleEnded(int channel) {
+    if (channel < 0 || 3 < channel) {
+      System.err.println("The channel needs to be from 0 to 3");
+      throw new IllegalArgumentException("Unexpected channel");
+    }
+
+    if (channel != this.channel) {
+      int config = 0x0183;                    // start with the default value from datasheet
+      config &= ~0x100;                       // enable continuous readings
+      config |= (range << 9);                 // set selected range (gain)
+      config |= (1 << 14) | (channel << 12);  // set single-ended and channel
+      config |= (1 << 15);                    // start a single conversion
+      writeRegister(0x01, config);            // write to the configuration register at 0x01
+
+      // when the channel switched we need to wait for the upcoming
+      // conversion to finish
+      delay(conversionDelay);
+
+      // save the channel so that we don't need to do the same for
+      // subsequent reads from the same channel
+      this.channel = channel;
+    }
+
+    return readS16(0x00) >> bitShift;  // read from the conversion register at 0x00
+    // the ADS1015 will have its 12-bit result in the upper bits, shift those right by four
+  }
+
+  protected void writeRegister(int register, int value) {
+    beginTransmission(address);
+    write(register);
+    write(value >> 8);
+    write(value & 0xFF);
+    endTransmission();
+  }
+
+  protected int readS16(int register) {
+    beginTransmission(address);
+    write(register);
+    byte[] in = read(2);
+    return (in[0] << 8) | in[1];
+  }
+}

java/libraries/io/examples/AnalogDigital_I2C_ADS1X15/AnalogDigital_I2C_ADS1X15.pde

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+import processing.io.*;
+ADS1015 adc;
+// or, alternatively:
+// ADS1115 adc;
+
+// see setup.png in the sketch folder for wiring details
+
+void setup() {
+  //printArray(I2C.list());
+
+  adc = new ADS1015("i2c-1", 0x48);
+  //adc = new ADS1115("i2c-1", 0x48);
+
+  // this sets the measuring range to +/- 4.096 Volts
+  // other ranges supported by this chip:
+  // INTERNAL_6V144, INTERNAL_2V048, INTERNAL_1V024,
+  // INTERNAL_0V512, INTERNAL_0V256
+  adc.analogReference(ADS1X15.INTERNAL_4V096);
+
+  // Important: do not attempt to measure voltages higher than
+  // the supply voltage (VCC) + 0.3V, meaning that 3.6V is the
+  // absolut maximum voltage on the Raspberry Pi. This is
+  // irrespective of the analogReference() setting above.
+}
+
+void draw() {
+  // this will return a number between 0 and 1
+  // (as long as your voltage is positive)
+  float measured = adc.analogRead(0);
+
+  // multiply with the selected range to get the absolut voltage
+  float volts = measured * 4.096;
+  println("Analog Input 0 is " + volts + "V");
+
+  background(255);
+  fill(measured * 255);
+  ellipse(width/2, height/2, width * 0.75, width * 0.75);
+}