main.c

A2D AD7887 accessed via SPI on a HCS12

/*
Travis Lytle 
This project takes data from an A2D via SPI and displays it via SCI to a terminal the voltage applied
in hex and in volts.
SPI A2D using AD7887 - http://www.analog.com/static/imported-files/data_sheets/AD7887.pdf
Using HCS12 S12UB board 

HC12				A2D			PIN
SCLK----------------CLK			8
SS------------------Chip Select	1
MOSI----------------DIN			6
MISO----------------DOUT		7
*/

#include <hidef.h>      // common defines and macros
#include <mc9s12dg128.h>     // derivative information
#pragma LINK_INFO DERIVATIVE "mc9s12dg128b"
#include <stdio.h>

void initSPI0(void);
uint ad7887(uchar);

void initSCI0(void);
char getChar(void), getString(char *);
void putChar(char), putString(char *);

uint a2dresult, ones, tenths, hundredths;
char volts[25];
ulong a2d, temp;

void main(void) 
{
  uchar ch;

  initSPI0();
  initSCI0();		

   while(1)	
   {
    ch = getChar();						//used to check for keyboard input

      if(ch == 0x20){					//checks for space key input
      a2dresult = ad7887(0x21);			//queries the A2D


      temp = (ulong)a2dresult * 1221;
      ones = temp / 1000000;
      temp = (temp - (1000000* ones));
      tenths = temp/100000;
      temp = (temp - (100000*tenths));
      hundredths = temp /10000;

      sprintf(volts, "Hex:%4X Voltage:%d.%d%d", a2dresult, ones, tenths, hundredths);
      putString(volts);
      putString("\n\r");
      }
   }
}

void initSPI0(void) 
{
 SPI0CR1 = 0x5E;  			//SPI on, set to master, and clock phase bit  CPOL, CPHA, SSOE on
 SPI0CR2 = 0x10;  			//MODFEN enabled
 SPI0BR = 0x77;         	//SPI Baud Rate
}

uint ad7887(uchar cr)
{  
  uchar ub, lb;				//upper and lower bytes
  uint ad;					//upper and lower bytes in one variable
  
  while (!(SPI0SR & 0x20));		
  SPI0DR = cr;				//control register
  while (!(SPI0SR & 0x80));		
  ub = SPI0DR;     			//recieve dummy data

  while (!(SPI0SR & 0x20));		
  SPI0DR = cr;				//control register
  while (!(SPI0SR & 0x80));		 
  lb = SPI0DR;

  ad = ub <<8;
  ad = ad | lb;    
  return ad;     //return data
}

void initSCI0() {
  char x;
  SCI0BDH = 0x00; 	//Baud Rate H Byte
  SCI0BDL = 26;  	//Baud Rate L Byte  9600 Baud
  SCI0CR1 = 0x00;  	
  SCI0CR2 = 0x0C; 	//TE and RE enabled
  x = SCI0SR1;     	//status reg    clears RDRF flag
  x = SCI0DRL;     	//data reg
}

char getString(char *buf)
{
  while((*buf++ = getChar()) != 0x0D){;}
  *buf = 0;  //terminate string with a NULL char  
}

void putString(char *cx)
{
  while((*cx)) 
  {
    putChar(*cx);
    cx++;
  }
}
/* gets  a char from the serial input.
waits for RDRF flag, which is recieve data registry full*/
char getChar(void) 
{
  while((SCI0SR1 & 0x20) == 0x00);
  return (SCI0DRL);
}
/* puts  a char to the serial input.
waits for TDRE flag, which is transmit data registry empty*/
void putChar(char cx)
{ 
  while(!(SCI0SR1 & 0x80));       //comment line out so data is sent rapidly and buffer does not get cleared
  SCI0DRL = cx; 
}