Added support for MCP4725’s power-down mode

Adafruit_MCP4725.cpp

@@ -33,7 +33,12 @@
     @brief  Instantiates a new MCP4725 class
 */
 /**************************************************************************/
-Adafruit_MCP4725::Adafruit_MCP4725() {
+Adafruit_MCP4725::Adafruit_MCP4725(uint8_t addressPin) {
+  _addressPin = addressPin;
+
+  if(_addressPin != MCP4725_ADDRESS_PIN_DISABLED) {
+    pinMode(_addressPin, OUTPUT);
+  }
 }
 
 /**************************************************************************/
@@ -44,7 +49,6 @@ Adafruit_MCP4725::Adafruit_MCP4725() {
 void Adafruit_MCP4725::begin(uint8_t addr) {
   _i2caddr = addr;
   Wire.begin();
-
 }
 
 /**************************************************************************/
@@ -62,25 +66,61 @@ void Adafruit_MCP4725::begin(uint8_t addr) {
                 after power-down or reset.
 */
 /**************************************************************************/
-void Adafruit_MCP4725::setVoltage( uint16_t output, bool writeEEPROM )
-{
+void Adafruit_MCP4725::setVoltage(uint16_t output, bool writeEEPROM) {
+  uint8_t controlBits = writeEEPROM ? MCP4726_CMD_WRITEDACEEPROM : MCP4726_CMD_WRITEDAC;
+  writeI2cPacket(controlBits, output);
+}
+
+void Adafruit_MCP4725::setAddressPin(bool enable) {
+  if(_addressPin != MCP4725_ADDRESS_PIN_DISABLED) {
+    digitalWrite(_addressPin, enable);
+  }
+}
+
+void Adafruit_MCP4725::writeI2cPacket(uint8_t controlBits, uint16_t dataBits) {
+setAddressPin(true);
+
 #ifdef TWBR
   uint8_t twbrback = TWBR;
   TWBR = ((F_CPU / 400000L) - 16) / 2; // Set I2C frequency to 400kHz
 #endif
   Wire.beginTransmission(_i2caddr);
-  if (writeEEPROM)
-  {
-    Wire.write(MCP4726_CMD_WRITEDACEEPROM);
-  }
-  else
-  {
-    Wire.write(MCP4726_CMD_WRITEDAC);
-  }
-  Wire.write(output / 16);                   // Upper data bits          (D11.D10.D9.D8.D7.D6.D5.D4)
-  Wire.write((output % 16) << 4);            // Lower data bits          (D3.D2.D1.D0.x.x.x.x)
+  Wire.write(controlBits);
+  Wire.write(dataBits / 16);        // Upper data bits (D11.D10.D9.D8.D7.D6.D5.D4)
+  Wire.write((dataBits % 16) << 4); // Lower data bits (D3.D2.D1.D0.x.x.x.x)
   Wire.endTransmission();
 #ifdef TWBR
   TWBR = twbrback;
 #endif
+
+  setAddressPin(false);
+}
+
+float Adafruit_MCP4725::setNearestActualVoltage(uint16_t desiredOutputMilliVolts, uint16_t vrefMilliVolts, bool writeEEPROM) {
+  float dacStepsPerMillivolt = 4095.0 / vrefMilliVolts;
+  uint16_t nearestDacInputCodeForVoltage = round(dacStepsPerMillivolt * desiredOutputMilliVolts);
+
+  float nearestVoltage = (vrefMilliVolts / 4095.0) * nearestDacInputCodeForVoltage;
+
+  setVoltage(nearestDacInputCodeForVoltage, writeEEPROM);
+  return nearestVoltage;
+}
+
+void Adafruit_MCP4725::powerDown(uint8_t loadResistance, bool writeEEPROM) {
+  uint8_t controlBits = writeEEPROM ? MCP4726_CMD_WRITEDACEEPROM : MCP4726_CMD_WRITEDAC;
+
+  switch (loadResistance) {
+    case MCP4725_OUTPUT_LOAD_RESISTANCE_1K:
+      controlBits |= 0x2;
+      break;
+    case MCP4725_OUTPUT_LOAD_RESISTANCE_100K:
+      controlBits |= 0x4;
+      break;
+    case MCP4725_OUTPUT_LOAD_RESISTANCE_500K:
+    default:
+      controlBits |= 0x6;
+      break;
+  }
+
+  writeI2cPacket(controlBits, 0x0);
 }

Adafruit_MCP4725.h

@@ -1,3 +1,6 @@
+#ifndef adafruit_mcp4725_h
+#define adafruit_mcp4725_h
+
 /**************************************************************************/
 /*! 
     @file     Adafruit_MCP4725.h
@@ -25,15 +28,27 @@
 
 #include <Wire.h>
 
-#define MCP4726_CMD_WRITEDAC            (0x40)  // Writes data to the DAC
-#define MCP4726_CMD_WRITEDACEEPROM      (0x60)  // Writes data to the DAC and the EEPROM (persisting the assigned value after reset)
+#define MCP4726_CMD_WRITEDAC                0x40  // Writes data to the DAC
+#define MCP4726_CMD_WRITEDACEEPROM          0x60  // Writes data to the DAC and the EEPROM (persisting the assigned value after reset)
+#define MCP4725_OUTPUT_LOAD_RESISTANCE_1K   0
+#define MCP4725_OUTPUT_LOAD_RESISTANCE_100K 1
+#define MCP4725_OUTPUT_LOAD_RESISTANCE_500K 2
+#define MCP4725_ADDRESS_PIN_DISABLED        255
 
 class Adafruit_MCP4725{
  public:
-  Adafruit_MCP4725();
+  Adafruit_MCP4725(uint8_t addressPin = MCP4725_ADDRESS_PIN_DISABLED);
   void begin(uint8_t a);  
-  void setVoltage( uint16_t output, bool writeEEPROM );
+  void setVoltage(uint16_t output, bool writeEEPROM);
+  float setNearestActualVoltage(uint16_t desiredOutputMilliVolts, uint16_t vrefMilliVolts, bool writeEEPROM);
+  void powerDown(uint8_t loadResistance, bool writeEEPROM);
 
  private:
   uint8_t _i2caddr;
+  uint8_t _addressPin;
+
+  void writeI2cPacket(uint8_t controlBits, uint16_t data);
+  void setAddressPin(bool enable);
 };
+
+#endif

examples/multiaddressing/multiaddressing.ino

@@ -0,0 +1,58 @@
+/**************************************************************************/
+/*!
+    @file     multiaddressing.ino
+    @author   Alex Mitchell (MitchellSoft Technology Ltd.)
+    @license  BSD (see license.txt)
+
+    This example shows how to address multiple MCP4725s on the same I2C bus.
+
+    One Arduino pin is required per MCP4725, which is used like a chip-select
+    pin.  For this reason, it only makes sense to address MCP4725s in this
+    way if you need more than two DACs in your project and they all have the
+    same address.  Otherwise, you will be using up Arduino pins needlessly.
+
+    This is an example sketch for the Adafruit MCP4725 breakout board
+    ----> http://www.adafruit.com/products/935
+
+    Adafruit invests time and resources providing this open source code,
+    please support Adafruit and open-source hardware by purchasing
+    products from Adafruit!
+*/
+/**************************************************************************/
+#include <Wire.h>
+#include <Adafruit_MCP4725.h>
+
+Adafruit_MCP4725 dac1(2); // ADDR pin of MCP4725 connected to Arduino pin 2
+Adafruit_MCP4725 dac2(3); // ADDR pin of MCP4725 connected to Arduino pin 3
+Adafruit_MCP4725 dac3(4); // ADDR pin of MCP4725 connected to Arduino pin 4
+
+void setup(void) {
+  Serial.begin(9600);
+  Serial.println("Hello!");
+
+  // The begin method must be called with the address of the MCP4725 when ADDR pin is tied to VCC
+  // For Adafruit MCP4725A1 this is 0x63
+  // For MCP4725A0 this is 0x61
+  // For MCP4725A2 this is 0x65
+  dac1.begin(0x63);
+  dac2.begin(0x63);
+  dac3.begin(0x63);
+
+  Serial.println("Example sketch demonstrating addressing multiple MCP4725s");
+}
+
+void loop(void) {
+  Serial.println("Setting 3 different lower voltage outputs");
+  dac1.setVoltage(100, false);
+  dac2.setVoltage(200, false);
+  dac3.setVoltage(300, false);
+
+  delay(5000);
+
+  Serial.println("Setting 3 different higer voltage outputs");
+  dac1.setVoltage(1000, false);
+  dac2.setVoltage(2000, false);
+  dac3.setVoltage(3000, false);
+
+  delay(5000);
+}

examples/powerdown/powerdown.ino

@@ -0,0 +1,59 @@
+/**************************************************************************/
+/*!
+    @file     powerdown.ino
+    @author   Alex Mitchell (MitchellSoft Technology Ltd.)
+    @license  BSD (see license.txt)
+
+    This example shows how to put the MCP4725 into power-down mode.
+    During power-down mode, the device draws about 60 nA, compared
+    against 200 µA (typical) when running in normal mode.
+
+    When in power-down mode, the output pin is connected to ground via
+    a configurable pull-down resistance of either 1K, 100K, or 500K Ohms.
+
+    To bring the device out of power-down mode, simply call setVoltage
+    (it will also wake up if an I2C General Call Wake-Up Command is sent
+    on the I2C bus).
+
+    This is an example sketch for the Adafruit MCP4725 breakout board
+    ----> http://www.adafruit.com/products/935
+
+    Adafruit invests time and resources providing this open source code,
+    please support Adafruit and open-source hardware by purchasing
+    products from Adafruit!
+*/
+/**************************************************************************/
+#include <Wire.h>
+#include <Adafruit_MCP4725.h>
+
+Adafruit_MCP4725 dac;
+
+void setup(void) {
+  Serial.begin(9600);
+  Serial.println("Hello!");
+
+  // For Adafruit MCP4725A1 the address is 0x62 (default) or 0x63 (ADDR pin tied to VCC)
+  // For MCP4725A0 the address is 0x60 or 0x61
+  // For MCP4725A2 the address is 0x64 or 0x65
+  dac.begin(0x62);
+
+  Serial.println("Example sketch demonstrating the MCP4725 power-down mode");
+}
+
+void loop(void) {
+  Serial.println("Putting MCP4725 to sleep.  Output pin connected to ground via 1K Ohm resistance.");
+  dac.powerDown(MCP4725_OUTPUT_LOAD_RESISTANCE_1K, false);
+  delay(5000);
+
+  Serial.println("Switching sleep mode.  Output pin now connected ot ground via 100K Ohm resistance.");
+  dac.powerDown(MCP4725_OUTPUT_LOAD_RESISTANCE_100K, false);
+  delay(5000);
+
+  Serial.println("Waking device up by setting an output voltage.");
+  dac.setVoltage(1000, false);
+  delay(5000);
+
+  Serial.println("Putting MCP4725 to sleep again.  Output pin connected to ground via 500K Ohm resistance.");
+  dac.powerDown(MCP4725_OUTPUT_LOAD_RESISTANCE_500K, false);
+  delay(5000);
+}

examples/setactualvoltage/setactualvoltage.ino

@@ -0,0 +1,67 @@
+/**************************************************************************/
+/*!
+    @file     setactualvoltage.ino
+    @author   Alex Mitchell (MitchellSoft Technology Ltd.)
+    @license  BSD (see license.txt)
+
+    This example shows how to set a voltage on the MCP4725 by specifying
+    the output voltage in millivolts, rather than calculating the raw output
+    value required by the MCP4725.
+
+    The MCP4725 has a resolution of 12 bits (4096 steps, from 0 to 4095), so 
+    it can get close, but not always output exactly the voltage requested.
+    In case this matters in your application, setNearestActualVoltage() returns
+    the value of the nearest voltage that could be generated by the MCP4725
+    so that your code can handle any discrepancies.
+
+    The reference voltage must be known and set for this to work.  The
+    reference voltage will often be 5V (5000mV), but especially when
+    running from USB power, it may be slightly off 5V.
+    Any difference between the reference voltage and the value specified
+    will create an inaccuracy in the voltage that the MCP4725 outputs.
+
+    This is an example sketch for the Adafruit MCP4725 breakout board
+    ----> http://www.adafruit.com/products/935
+
+    Adafruit invests time and resources providing this open source code,
+    please support Adafruit and open-source hardware by purchasing
+    products from Adafruit!
+*/
+/**************************************************************************/
+#include <Wire.h>
+#include <Adafruit_MCP4725.h>
+
+static const int REFERENCE_VOLTAGE_mV = 5000;
+static const bool WRITE_EEPROM = false;
+
+Adafruit_MCP4725 dac;
+
+void setup(void) {
+  Serial.begin(9600);
+  Serial.println("Hello!");
+
+  // For Adafruit MCP4725A1 the address is 0x62 (default) or 0x63 (ADDR pin tied to VCC)
+  // For MCP4725A0 the address is 0x60 or 0x61
+  // For MCP4725A2 the address is 0x64 or 0x65
+  dac.begin(0x62);
+
+  Serial.println("Example sketch demonstrating how to set a voltage with the MCP4725");
+}
+
+void loop(void) {
+  Serial.println("Outputting 0V");
+  dac.setNearestActualVoltage(0, REFERENCE_VOLTAGE_mV, WRITE_EEPROM);
+  delay(5000);
+
+  Serial.println("Requesting 2500mV (2.5V)");
+  float nearestMillivoltsPossible = dac.setNearestActualVoltage(2500, REFERENCE_VOLTAGE_mV, WRITE_EEPROM);
+  Serial.print("Nearest value to 2500mV that the MCP4725 could output is: ");
+  Serial.print(nearestMillivoltsPossible);
+  Serial.println("mV");
+  delay(5000);
+
+  Serial.println("Outputting 5000mV (5V)");
+  dac.setNearestActualVoltage(5000, REFERENCE_VOLTAGE_mV, WRITE_EEPROM);
+  delay(5000);
+  Serial.println("******");
+}

examples/sinewave/sinewave.ino

@@ -1,6 +1,6 @@
 /**************************************************************************/
 /*!
-    @file     sinewave.pde
+    @file     sinewave.ino
     @author   Adafruit Industries
     @license  BSD (see license.txt)
 

examples/trianglewave/trianglewave.ino

@@ -1,6 +1,6 @@
 /**************************************************************************/
 /*! 
-    @file     trianglewave.pde
+    @file     trianglewave.ino
     @author   Adafruit Industries
     @license  BSD (see license.txt)