// Reading REG values and voltage out of DAC1 and DAC2 ports
  // DFRobot Firebeetle ESP32 dev board.

  void loop()
    {
  
      int a = 20;
      int b = 120;


      dacWrite(25,a);
      dacWrite(26,b);


     Serial.println(a);
     Serial.println(b);

     Serial.println((READ_PERI_REG(RTC_IO_PAD_DAC1_REG)),HEX);
     Serial.println((READ_PERI_REG(RTC_IO_PAD_DAC1_REG)),BIN);
     Serial.println((READ_PERI_REG(RTC_IO_PAD_DAC2_REG)),HEX); 
     Serial.println((READ_PERI_REG(RTC_IO_PAD_DAC2_REG)),BIN);
      
     Serial.println((READ_PERI_REG(SENS_SAR_DAC_CTRL1_REG)),HEX);
     Serial.println((READ_PERI_REG(SENS_SAR_DAC_CTRL1_REG)),BIN);
     Serial.println((READ_PERI_REG(SENS_SAR_DAC_CTRL2_REG)),HEX);
     Serial.println((READ_PERI_REG(SENS_SAR_DAC_CTRL2_REG)),BIN); 

    }

Results below from running above code.....

20
120
80A60400
10000000101001100000010000000000
83C60400
10000011110001100000010000000000
0
0
0
0


For int 20 volts out is 2.82 volts
For int 120 volts out is 1.63 volts.
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160
240
85060400
10000101000001100000010000000000
87860400
10000111100001100000010000000000
0
0
0
0
For int 160 Volts out is 2.0 volts
For int 240 volts out is 3.0 volts
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Now if I put in this config for I2S.......

int i2s_num = 0;      // i2s port number DAC BUILT_IN  works on I2S_NUM_0

i2s_config_t i2s_config = {
     .mode = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX | I2S_MODE_DAC_BUILT_IN),
     .sample_rate =44100,
     .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
     .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
     .communication_format = (I2S_COMM_FORMAT_I2S_MSB),
     .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,        // high priority Interrupt level 1
     .dma_buf_count = 2,
     .dma_buf_len = 128   
    };


        i2s_set_pin((i2s_port_t)i2s_num, NULL);  // NULL for BUILT_IN DAC
         
        i2s_driver_install((i2s_port_t)i2s_num, &i2s_config, 0, NULL);




Below is with I2S config.....

160
240
85060400
10000101000001100000010000000000
87860400
10000111100001100000010000000000
2400000
10010000000000000000000000
0
0
Now get.....
For int 160 Volts out is 3.0 volts
For int 240 volts out is 3.0 volts
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20
120
80A60400
10000000101001100000010000000000
83C60400
10000011110001100000010000000000
2400000
10010000000000000000000000
0
0
Now get.....
For int 20 Volts out is 3.0 volts
For int 120 volts out is 3.0 volts
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