Analog Devices AD56X4 12/14/16-Bit Quad Channel DAC Arduino Library

An Arduino library to control an Analog Devices AD56X4 series 12/14/16-bit Quad channel DAC (Digital to Analog Converter) by SPI. This library interfaces the following chips

• AD5624 : 12-bit
• AD5664 : 16-bit
• AD5624R : 12-bit with an internal voltage reference that can be used
• AD5644R : 14-bit with an internal voltage reference that can be used
• AD5664R : 16-bit with an internal voltage reference that can be used

Copyright (c) 2013, Freja Nordsiek

This software is distributed under a 2-Clause BSD License.

Making The Library Package

On a system with make, the provided Makefile can be used to build a .zip file containing the whole library by simply running make or make package. The package will be named AD65X4_VERSION.zip where VERSION is the current package version.

Hardware Information

All the AD56X4 series are connected in a similar way in order for the Arduino to communicate with it by SPI (Serial Peripheral Interface). The DIN pin on the chip (pin 8 on the MSOP and LFCSP packages and pin C1 on the WLCSP package) corresponds to the Arduino's MOSI pin (pin 11 on the Uno, pin 51 on the Mega, and ICSP-4 on all that have the ICSP header). The SCLK pin on the chip (pin 7 on the MSOP and LFCSP packages and pin D1 on the WLCSP package) corresponds to the Arduino's SCK pin (pin 13 on the Uno, pin 52 on the Mega, and ICSP-3 on all that have the ICSP header). The SYNC pin on the chip (pin 6 on the MSOP and LFCSP packages and pin D2 on the WLCSP package) is the Slave Select (SS) pin, which might as well be the Arduino's SS pin (pin 10 on the Uno and pin 53 on the Mega). The SS pin to use has to be given as the first argument of every public function in this library (makes it easier to have multiple SPI devices with different SS pins).

The chip can receive data by SPI at speeds up to 50 MHz, which is significantly greater than the Uno and Mega can do at the present time (8 MHz as of 2013-08-20). So, the SPI clock divider setting doesn't really matter except for how long it will take for commands to complete.

The chips all use a voltage reference that is the upper rail for the analog outputs and determines the resolution of the output voltage. All the chips can take an external voltage reference (pin 16 on the MSOP and LFCSP and pin A1 on the WFCSP). The AD56X4R series have an internal voltage reference that can optionally be used instead (off by default). It is 1.25 V for the AD56X4R-3 series and 2.5 V for the AD56X4R-5 series.

Using The Library

An Arduino program using this library must first include the library header in addition the the SPI library header.

#include <SPI.h>
#include <AD56X4.h>

All library functions require that the Arduino pin that is the Slave Select for the AD654X (SYNC pin on the device) be given as the first argument. Hence, the calling format looks like

AD56X4.function(AD56X4_SS_pin, ...);

When initializing, the Arduino's Slave Select pin (10) must be set to OUTPUT in addition to whatever pin is used for the Slave Select of the AD56X4 device (pin 10 is a good candidate to avoid wasting a pin). As the AD56X4 device can work with up to 50 MHz SPI messages while the Arduino's maximum speed at the time of this writing (2013-08-20) is 8 MHz, the particular clock divider setting doesn't really matter, though setting it as fast as possible to SPI_CLOCK_DIV2 will reduce the time it takes to give the AD56X4 commands. Unless it is desirable to keep the previous state of the AD65X4 on Arduino power up or reset, one should do a full reset of the device with AD56X4.reset(AD56X4_SS_pin, true). An initialization sequence would look like

pinMode(10,OUTPUT);
pinMode(AD56X4_SS_pin,OUTPUT);
SPI.setClockDivider(SPI_CLOCK_DIV2);
SPI.begin();

AD56X4.reset(AD56X4_SS_pin,true);

Note, when any library function is called, the SPI Bit Order is set to MSBFIRST and the SPI Data Mode is set to SPI_MODE1. These are not changed back at the end of the function call, so they will need to set before using the SPI bus with another device.

The AD56X4 series DACs all have the value they are outputting and a buffer holding the next value to output. These are referred to as the DAC and input registers respectively. Setting the input registers (function AD56X4.setChannel) does not change the analog voltages on the channels unless the AD56X4 is told to update the output (DAC register) at the same time (optional set modes AD56X4_SETMODE_INPUT_DAC or AD56X4_SETMODE_INPUT_DAC_ALL) or that is the default setting for the channel (function AD56X4.setInputMode). The function AD56X4.updateChannel is used to update the output (DAC register) to the current value of the input register.

Example Code

An example program, Four_Sine_Waves, is provided that writes 10 Hz sine waves to each channel that are out of phase with each other in 90 degree increments.

Library Functions

• void AD56X4.setChannel(int SS_pin, byte setMode, byte channel, word value)
  void AD56X4.setChannel(int SS_pin, byte setMode, word values[])
  void AD56X4.setChannel(int SS_pin, byte setMode, word value_D, word value_C, word value_B, word value_A)
  

  Sets the value/s of the specified channel/s on the chip (Slave Select pin SS_pin). Values (last argument/s) have to be word types (unsigned 16-bit integers, which are unsigned int as well). For 12 and 14-bit chips, the last 4 and 2 bits respectively are ignored. setMode specifies how the registers are set when the channels/s are set, and the valid values are listed below

  • AD56X4_SETMODE_INPUT Set only the input register (doesn't change voltage output).
  • AD56X4_SETMODE_INPUT_DAC Set both the input and DAC registers (voltage output is updated).
  • AD56X4_SETMODE_INPUT_DAC_ALL Set the input register for that channel and cause all input registers to then be copied into their respective DAC registers (output updated on all channels).

  For the first overload (calling method), only one channel (or all channels) are set to value (or all channels set to it). The valid values of channel are

  • AD56X4_CHANNEL_A Channel A only.
  • AD56X4_CHANNEL_B Channel B only.
  • AD56X4_CHANNEL_C Channel C only.
  • AD56X4_CHANNEL_D Channel D only.
  • AD56X4_CHANNEL_ALL All channels.

  They CANNOT be bitwise OR'ed together. In the second and third calling overloads, each channel is set to the given values, which can either be a 4-element array (channel D to A order) or four separate arguments.

• void AD56X4.updateChannel(int SS_pin, byte channel)
  

  For the chip with the Slave Select pin SS_pin, the DAC register (and therefore voltage output) of the specified channel (see setChannel above for how channels are specified) is set to the value of its input register. If setChannel was called with setMode = AD56X4_SETMODE_INPUT, then this function will have to be called on the channel in order for the output voltage to be updated.

• void AD56X4.powerUpDown(int SS_pin, byte powerMode, boolean channels[])
  void AD56X4.powerUpDown(int SS_pin, byte powerMode, boolean channel_D, boolean channel_C, boolean channel_B, boolean channel_A)
  void AD56X4.powerUpDown(int SS_pin, byte powerModes[])
  

  For the chip with the Slave Select pin SS_pin, the power state/mode of the channels are set. The valid power mode/s are

  • AD56X4_POWERMODE_NORMAL On.
  • AD56X4_POWERMODE_POWERDOWN_1K Off and connected by a 1k resistor to ground.
  • AD56X4_POWERMODE_POWERDOWN_100K Off and connected by a 100k resistor to ground.
  • AD56X4_POWERMODE_TRISTATE Off in a tri-state operation.

  For the first and second overloads (function calling methods), one power mode powerMode is applied to the specified channels. The channels are specified either as a 4-element boolean array (channel D to A order) or as four boolean arguments. true means set to the given power mode and false means not (keep current power mode). The third overload sets the power mode of each channel to the power modes given in the 4-element array powerModes[] (channel D to A order).

• void AD56X4.reset(int SS_pin, boolean fullReset)
  

  Resets the AD56X4 chip with Slave Select pin SS_pin. The DAC and input registers are all reset to 0, and thus the analog voltages are set to zero. If fullReset is true, then a full reset is done which resets the channel powerMode to on (AD56X4_POWERMODE_NORMAL), the external voltage reference is used (internal reference, if present, turned off), and the input mode (LDAC register in the chip data sheet) is reset (updating the input registers does not cause automatic updates of the DAC registers from their values).

• void AD56X4.setInputMode(int SS_pin, boolean channels[])
  void AD56X4.setInputMode(int SS_pin, boolean channel_D, boolean channel_C, boolean channel_B, boolean channel_A)
  

  Sets the input modes of each channel on the chip (Slave Select pin SS_pi). The modes are boolean with true meaning that setting the input register automatically sets the DAC register (and therefore voltage output) to the same value and false meaning no auto update of the DAC register. The modes for each channel can either be given by a 4-element boolean array (channel D to A order) or as four separate input arguments.

• void AD56X4.useInternalReference (int SS_pin, boolean yesno)
  

  Choose whether the chip (Slave Select pin SS_pin) uses the internal voltage reference (yesno = true) or the external reference pin (yesno = false). Only applicable for the chips that have an internal reference (AD56XR).