Arduino Nano Controlling AD5372 DAC using SPI

I have previously asked for help before, but after a week or so of playing around and trying to get it to work I am back. Attached below is the code I am using to try and write to the AD5372, which is a 16-bit, 32 channel DAC. pin 13 is CLK, pin 10 is SS, pin 11 is MOSI, and pin 16 is Load DAC, which is proprietary to this DAC I believe (should load registers I think???). I know that the SPI.begin command should set most of these pins to outputs already, but this was just one of my trial and error attempts to get the code working. I have attached the timing characteristics as well as what the data sheet mentions about the SPI interface of the DAC.

#include <SPI.h>
int LDAC = 16;

void setup (void)
  pinMode(SS, OUTPUT);
  pinMode(LDAC, OUTPUT); ensure LDAC is output
  pinMode(11, OUTPUT); //ensure MOSI is output
  pinMode(13, OUTPUT); //ensure SCK is output
  digitalWrite(SS, HIGH);  // ensure SS stays high
  digitalWrite(LDAC, HIGH); // ''
  SPI.begin ();
  delay (1000);  // 1 seconds delay

  byte com = 0b11;//sets to write mode
  byte address = 0b000000;//Sets DAC to write to all channels
  int data = 0b1111111111000000;
  // enable Slave Select
  digitalWrite(SS, LOW);    // SS is pin 10, falling edge starts write
  // send string
 digitalWrite(SS, HIGH);// disable Slave Select

 digitalWrite(LDAC, LOW);
 digitalWrite(LDAC, HIGH);

void loop (void)


  1. You should have continued the previous thread, it contains relevant information.

  1. How are reset/, clear/ and busy/ being handled? I see nothing in the code which sets those pins to outputs and pulls them low. That means they’re high impedance inputs which will prevent the chip from operating.

  2. Have you addressed the need for an external VREF?

Sorry about that, thanks for linking it! I have them tied to pins on the arduino, but for my purposes I thought that they were not necessary at this point since I am only trying to write to the DAC. Could you elaborate about the external VREF? Attached is an image of the relevant portion of the schematic.

I am currently reading more about the VREF. I can't believe I overlooked this, thank you for your insight!

Unfortunately, not having a set VREF seems to only add to the list of issues. luckily I have access to an eval board, which is operational with Analog Devices proprietary software, however it can be operated in a standalone setting, which allows the user to connect directly to the MOSI, SS, SCK, LDAC, BUSY, etc.

Needless to say the code still did work. I have attached an image of the set up. It has a jumper setting the VREF to 3V, I have the jumper off to set it to standalone setting. Basically, it should show that the issue is on the end with my coding.