How do i fill the second byte?

Question

I am using I2C communications to control a AD5694RBRUZ (http://www.analog.com/media/en/technical-documentation/data-sheets/AD5696R_5695R_5694R.pdf) with my Arduino Nano. If i enter two bytes it wil Wire.write only the first line from top to bottom. In the datasheet it is shown that you muust first fill the command byte, then the high and last the low byte. How can i fill the low byte? I have now scraped the idea to input two bytes separately and decided to input one uint16_t byte. How do i fill the low byte at the same time as the high byte, or if it possible how to input the uint16_t value?

My code is as follows:

#include <Wire.h>

#define Address 0x0D

void setup()
{
Serial.begin(9600);
Wire.begin();
AddressWrite(0x3F,0x05B0);
Serial.print ("Biti = ");
Serial.println (AddressRead(0x01));
}

void loop()
{
}

void AddressWrite (byte Naslov, uint16_t Cifra1)
{
byte Hi, Lo;
Hi = highByte(Cifra1);
Lo = lowByte(Cifra1);
Wire.beginTransmission(Address);
Wire.write(Naslov);
Wire.write(Cifra1);
Wire.endTransmission();
Serial.print ("Biti Hi = ");
Serial.println (Hi);
Serial.print ("Biti Lo = ");
Serial.println (Lo);
Serial.print ("Biti Cifra = ");
Serial.println (Cifra1);
}

byte AddressRead (byte naslov)
{
Wire.beginTransmission(Address);
Wire.write(naslov);

Wire.requestFrom(Address,2);

while(!Wire.available())
  {
  }

return Wire.read();
}

Thank you for your time and help.

Answer 1

You can use a number of Wire.write to write data. The AD5694R should get three bytes and two bytes can be read from it. There is a "multiple dac readback sequence", but that is an extra.

Your AddressWrite requires an extra Wire.write.
Your AddressRead is missing a Wire.endTransmission and the while(!Wire.available()) should be removed.

void AddressWrite (byte Naslov, uint16_t Cifra1)
{
  byte Hi, Lo;
  Hi = highByte(Cifra1);
  Lo = lowByte(Cifra1);

  Wire.beginTransmission(Address);
  Wire.write(Naslov);       // command byte
  Wire.write(Hi);           // msb first
  Wire.write(Lo);           // lsb second
  Wire.endTransmission();
}

uint16_t AddressRead (byte naslov)
{
  Wire.beginTransmission(Address);
  Wire.write(naslov);       // command byte
  Wire.endTransmission(false);  // repeated start

  uint16_t hi, lo, result;
  Wire.requestFrom(Address,2);
  hi = Wire.read();
  lo = Wire.read();
  result = word(hi,lo); 
  return result;
}

I have added a repeated start, because that is according to the datasheet.

Could you make the names more according to the datasheet ? For example 'command' or 'commandByte' instead of 'Naslow'. And perhaps better names for the functions, for example 'writeAD5694R' instead of 'AddressWrite'.