print value from 24 bit register of adc

Projects Programming
1

Hi,
I am new to arduino.
I want to print 24 bit value from an adc register .Will the following do?
//read adc register
byte High=SPI.transfer(0x00);
byte Middle=SPI.transfer(0x00);
byte low=SPI.transfer(0x00);
adcvalue=(High<<16) | (Middle<< 8 ) | (low);
Serial.print(adcvalue);

In the above,is it ensured that the most signigicant 8 bits will go to "High" variable.middle 8 bits to "Middle" variable and least significant 8 bits to "low" variable?

2

How is adcvalue declared ?

3

you can do qa first check and print the individual bytes to check if anything comes in...

4

I'd cast the byte values to "unsigned long" before shifting.

5

Also make sure that is the older that the SPI ADC transfers it's value. A datasheet will answer that.

6

You could try something like this:

  union{
    unsigned long adcvalue;
    struct{
       byte low;
       byte mid;
       byte high;
       byte zero;
    };
  } converter;
  converter.zero = 0;
  converter.high=SPI.transfer(0x00);
  converter.mid=SPI.transfer(0x00);
  converter.low=SPI.transfer(0x00);
  Serial.print(converter.adcvalue);

I'm just a fan of unions is all :smiley:

7

And in the tradition of true K&R C language usage. :wink:

8

Such a shame they're not that portable.

9

Hi,

I am not getting the output.Now,when I try to read the id,the output is printed as 3,instead of 2.
My code to read AD7193 id is given below.

#include <SPI.h>
void setup()
{
  Serial.begin(9600);
  SPI.begin(4);
  SPI.setClockDivider(4,21);
  pinMode(4,OUTPUT);


}

void loop()
{
 digitalWrite(4,LOW);
 SPI.transfer(4,0x60,SPI_CONTINUE);//command for communication  register to read id register
 byte result = SPI.transfer(4,0x00,SPI_CONTINUE);//read id reg value
 Serial.println(result&0x0F);//id is 2
 delay(1000);

}
10

uaim:
Hi,

I am not getting the output.Now,when I try to read the id,the output is printed as 3,instead of 2.
My code to read AD7193 id is given below.

#include <SPI.h>

void setup()
{
  Serial.begin(9600);
  SPI.begin(4);
  SPI.setClockDivider(4,21);
  pinMode(4,OUTPUT);

}

void loop()
{
digitalWrite(4,LOW);
SPI.transfer(4,0x60,SPI_CONTINUE);//command for communication  register to read id register
byte result = SPI.transfer(4,0x00,SPI_CONTINUE);//read id reg value
Serial.println(result&0x0F);//id is 2
delay(1000);

}

11

Here is a different solution, use it just like a const uint32

struct{
  operator uint32_t() const {
    return (uint32_t( SPI.transfer(0x00) ) << 16) + (SPI.transfer(0x00) << 8) + SPI.transfer(0x00);
  }
} ADC_24Bit;

//Then to print or read the live value:
Serial.print( ADC_24Bit, HEX );