Problem with output IOUTA and IOUTB of DAC8812

/*Demo codes for testing DAC8812*/

#include <Arduino.h>
#include <SPI.h> 


//Full functionality demo code

// DAC8812 Pin Definitions
#define CS_PIN 5      // Chip Select (CS) pin
#define LDAC_PIN 4    // Load DAC (LDAC) pin
#define RS_PIN 16     // Reset (RS) pin

// SPI settings
SPISettings DAC8812_settings(1000000, MSBFIRST, SPI_MODE0);

void setup() {
  // Initialize Serial Monitor for debugging
  Serial.begin(115200);

  // Configure SPI
  SPI.begin();  // Initializes the SPI bus

  // Configure control pins
  pinMode(CS_PIN, OUTPUT);
  pinMode(LDAC_PIN, OUTPUT);
  pinMode(RS_PIN, OUTPUT);
  
  // Set control pins to default states
  digitalWrite(CS_PIN, HIGH);  // CS should be high when not communicating
  digitalWrite(LDAC_PIN, HIGH);  // LDAC high to not update outputs
  digitalWrite(RS_PIN, HIGH);  // RS high to avoid reset


  Serial.println("DAC channels updated!");
}

void loop() {
  // Your main loop code can go here
  //digitalWrite(RS_PIN, HIGH);  // RS high to avoid reset
  programDAC8812(1, 0xFFFF);  // Set channel A to midscale (32768, mid value of 2^16)
 // programDAC8812(2, 0x4000);
  
}

void programDAC8812(byte channel, uint16_t value) {
  uint32_t command = 0x00000;  // Nota: el tamaño debe ser al menos 18 bits, por eso se usa un uint32_t

  // Configure the command based on the selected channel
  if (channel == 1) {
    command = 0b11 << 16;  // Set DAC A (A1:A0 = 01)
  } else if (channel == 2) {
    command = 0b10 << 16;  // Set DAC B (A1:A0 = 10)
  }
  
  // Combine the channel bits with the value
  command |= (value & 0xFFFF);  // Set the 16-bit value

  // Print the full 18-bit command in binary
  Serial.print("Channel: ");
  Serial.print(channel);
  Serial.print(", Value: 0x");
  Serial.print(value, HEX);
  Serial.print(" -> Command: 0b");
  for (int i = 17; i >= 0; i--) {
    Serial.print((command >> i) & 1);
  }
  Serial.println();

  // Begin SPI communication
  SPI.beginTransaction(DAC8812_settings);
  digitalWrite(CS_PIN, HIGH);
  digitalWrite(CS_PIN, LOW);
  // Split the 18-bit command into SPI transfers
  uint16_t firstPart = (command >> 2) & 0xFFFF;  // Extract the upper 16 bits
  uint8_t secondPart = (command & 0x3) << 6;     // Extract the lower 2 bits and shift them

  // Print the parts being transferred
  Serial.print("SPI.transfer16: 0x");
  Serial.println(firstPart, HEX);
  Serial.print("SPI.transfer: 0x");
  Serial.println(secondPart, HEX);

  // Send the data via SPI
  //SPI.transfer16(firstPart);
  uint8_t byte1 = (command >> 10) & 0xFF; // Primeros 8 bits (de B17 a B10)
  uint8_t byte2 = (command >> 2) & 0xFF;  // Siguientes 8 bits (de B9 a B2)
  uint8_t byte3 = (command & 0x3) << 6;   // Últimos 2 bits (de B1 a B0) desplazados a la izquierda

  // Enviar cada parte
  SPI.transfer(byte1);
  SPI.transfer(byte2);
  SPI.transfer(byte3);
  

  digitalWrite(CS_PIN, HIGH);  // End SPI communication
  digitalWrite(LDAC_PIN, LOW);
   // Short delay for LDAC pulse
  digitalWrite(LDAC_PIN, HIGH);
  //digitalWrite(CS_PIN, LOW);
  SPI.endTransaction();
 
}