spi6674.c

C2C-plus code that uses a 16F84 to read a thermocouple via a Maxim's Max6674. (by Ryan Dumouchel).

/* 
The spi6674 code bit bangs the thermocouple reading Max6674 and stores it in spihi (MSB)
and 3 bits in spilo (lsb).
*/

#include <system.h>
#include "spi6674.h"

void SPI_Setup(void)
{
 clear_bit(trisb, 0);  // Set up Relay bit
 set_bit(trisb, SO); //SO Line  input (1) RB1 2nd bit
 clear_bit(trisb, SCK);  //SCK Line is an output (0)  RB2 
 clear_bit(trisb, CS);  //CS  Chip Select as output RB3

}

void SPI_Read(void)
{

  clear_bit(portb, SCK);  //Initialization
  set_bit(portb, CS);
  spihi = 0;
  spilo = 0;
  delay_ms(250);
  clear_bit(portb, CS);

  //0
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spihi, 7); //Read SO on RB2 and set bit value of spihi
  clear_bit(portb, SCK);            //This is bit 15 and is a dummy bit
 // delay_ms(10);

  //1
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spihi, 6);  //This is bit 14 and is the MSB of reading
  clear_bit(portb, SCK);
//  delay_ms(10);

//2
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spihi, 5);
  clear_bit(portb, SCK);
 // delay_ms(10);

//3
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spihi, 4);
  clear_bit(portb, SCK);
 // delay_ms(10);  

//4
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spihi, 3);
  clear_bit(portb, SCK);
 // delay_ms(10);

  //5
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spihi, 2);
  clear_bit(portb, SCK);
 // delay_ms(10);  

  //6
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spihi, 1);
  clear_bit(portb, SCK);
//  delay_ms(10);

  //7
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spihi, 0);
  clear_bit(portb, SCK);
 // delay_ms(10);

  //Write Low Bit

  //0
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spilo, 2);
  clear_bit(portb, SCK);
  // delay_ms(10);

   //1
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spilo, 1);
  clear_bit(portb, SCK);
  //delay_ms(10);

   //2
  set_bit(portb, SCK);
  if (portb & 2) set_bit(spilo, 0);  //This is bit 5 that Max6674 outputs and is the LSB
  clear_bit(portb, SCK);             //Bits 0-4 are ignored
  //delay_ms(10);
}
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