Wsrtjtyk

I am trying to communicate to a MCP3426 ADC chip attached to an arduino shield using the I2C serial protocol and with little experience in...well anything there are quite a bunch of questions I have. First let me explain the system.

Currently, I have the MCP3426A1-E-S/N chip (datasheet found here: https://ww1.microchip.com/downloads/en/DeviceDoc/22226a.pdf) attached to a PCB that is connected to an arduino UNO using header pins. Vdd and Vss are connected to the 5V arduino power supply and GND respectively. Only one channel is being used with the positive input connected to an MCP4725 DAC and the negative input connected to a 2.5V reference voltage. Right now, I am simply trying to see if I can read a signal from the ADC without necessarily sending a signal through the DAC. This is the code I have written:

#include <Wire.h>



void setup(void) {

  Serial.begin(9600);

  Wire.begin();  

}



void loop(void) {

    int adcValueRead = 0;

    int adcValueRead1 =0;

    int adcValueRead2=0;



  //address of MCP3426A1-E/SN corresponding to 0b1101010

    Wire.beginTransmission(0x6A);



  //configuration register corresponding to 0b10001000 which is a one-shot 

  //conversion in channel 1 and a 16 bit resolution

    Wire.write(0x88); 



    delay(500);



  //requestion 3 bytes from the MCP3426 address

    Wire.requestFrom(0x6A, 3);

    adcValueRead= Wire.read();

    adcValueRead1=Wire.read();

    adcValueRead2=Wire.read();





    Serial.print("tADC Value: ");      

    Serial.print(adcValueRead);

    Serial.print(" ");

    Serial.print(adcValueRead1);

    Serial.print(" ");

    Serial.print(adcValueRead2);



    Serial.print('n');



}    

When I open the serial monitor the value that I get is:

ADC Value 0 21 16

So I have several questions, first of which being whether I correctly interpreted the datasheet and 0x6A is in fact the address and 0x88 is the correct configuration register for what I want. The relevant parts of the datasheet I believe can be found here:

address byte(datasheet pg. 20) and configuration resgister (datasheet pg. 18)

Now if I am interpreting the datasheet correctly, after the conversion I should be expecting three 8 bit bytes, with the first two being the voltage value in 16 bits and the third byte being the configuration register. So knowing that, I would expect my program to return

ADC Value 128 0 136

The reason I believe this is because the voltage difference between the two inputs should be 2.5V (since I'm not sending anything through the DAC) which, being half of 5V, should correspond to a 16 bit byte of 1000000000000000 and the third byte should be the same configuration register I sent originally. That, of course, is not what I got and I'm not sure why.

As you can probably tell, there are some pretty basic fundamental stuff I don't really understand and I am just trying to interpret the datasheet as correctly as I can. So is my interpretation of the system correct and is there something wrong with my code/connections or is my interpretation of the system incorrect and I should in fact be expecting "0 21 16" as my ADC values. Please let me know if there is any other information that needs to be known but any help in letting me understand my system would be greatly appreciated.