SM73201: Problem to read ADC by using Arduino

Hi Nicholas,

Thanks for the detail answer. I will try with your instruction and come to you with my code.

regards

Ahmed

Hi Nicholas,

Please see my code below but I didn't see any thing on serial port. I am using Arduino Micro 32U4 controller. Actuall I would like to read 0 to 1mv signal with 30uV step size. I have done my hardware part and trying to read by using programming. for next I will use Multiplexer 74HC154 for CS and read 12 differnt ADC by using single Arduino. Need your help in this regards and also guide me how I creat single/two clock pulse delay as you descibed previous for reading ADC.

Ahmed

#include <SPI.h>

/* SPI Pins used:
   MISO = 11
   SCK = 9
   CS = 27
   */


const int CS = 27; //Chip select output. Controls the slave device

int adcValue=0;//This is the value in the ADC output register
byte dummyByte;//Byte that does nothing but allows the conversion cycle to complete.
byte upperByte;//Most significant BIT
byte lowerByte;//Least significant BIT


void setup(){
  SPI.begin();//Enables the SPI interface 
  SPI.setDataMode(SPI_MODE0);
  pinMode(adcCS, OUTPUT);

    Serial.begin(9600);

  
//Reset cycle for the ADC. Initializes the chip on power up. Occurs only 1 time.  
digitalWrite (CS, LOW); 
dummyByte = SPI.transfer(0); // Initialization/Reset clocks
digitalWrite (CS,  HIGH);
  
}
  
  void loop(){
    // read out data from prior conversion, provide clocks for next conversion

digitalWrite (CS, LOW); //Enables SPI 
upperByte = SPI.transfer(0);  // read one byte of result back
lowerByte = SPI.transfer(0);  // read one byte of result back
dummyByte = SPI.transfer(0); // finish providing 18 clocks to complete conversion
digitalWrite (CS,  HIGH); //Disables SPI
adcValue = (upperByte<<8) + lowerByte; // Moves the upperByte to the left, then adds 
                                  //the lowerByte.  Combining the two equals the adcValue.
    

    
Serial.println(adcValue, DEC);//Prints the ADC Value to Serial port. 
float voltage = adcvalue * (2.048 / 65535.0);
Serial.println(voltage);//Prints the ADC Value to Serial port.
                                  
 
    delay(250);
}

Hello Ahmed,

I am not proficient using the Arduino , but if I follow your above code, then you need to modify as follows.

The 6 MSB's of the result will be in the UpperByte, the next 8 bits in the lowerByte, and the 2 LSB's in the dummyByte.

For the UpperByte, you need to shift left by 10, not 8.  The lowerByte will require a shift left of 2, and the dummyByte will need to Shift Right 6.  You would then combine (OR) all three values to get the final result.  If adcValue is a 32b integer, you will want to force the upper 16b's to 0 since the first bit output by the ADC is floating and could randomly read back as a 0 or 1.

Regards,

Keith