[PIC] Help reading data from MCP9808 with pic12f683 through I2C bus

[bgdev]

Hi I'm trying to read the temperature data from a sensor MCP9808 with a PIC12F683 through the i2c bus and then store it into the pic internal eeprom, working with mplab and XC8 C compiler.
From the MCP9808 datasheet, these are the steps:

i2c_start(); // send START command
i2c_write (AddressByte & 0xFE); //WRITE Command (see Section 4.1.4 “Address Byte”) also, make sure bit 0 is cleared ‘0’
i2c_write(0x05); // Write TA Register Address
i2c_start(); //Repeat START
i2c_write(AddressByte | 0x01); // READ Command (see Section 4.1.4 “Address Byte”) also, make sure bit 0 is Set ‘1’
UpperByte = i2c_read(ACK); // READ 8 bits and Send ACK bit
LowerByte = i2c_read(NAK); // READ 8 bits and Send NAK bit
i2c_stop(); // send STOP command

I have found a PIC12F675 bit banging library that should be fine for my purpose.

This is my code:

[B]Includes.h[/B]
#ifndef __INCLUDES_H
#define __INCLUDES_H

// Define CPU Frequency
// This must be defined, if __delay_ms()
// or __delay_us() functions are used in the code
#define _XTAL_FREQ 4000000     // Hz

// Include files
#include <xc.h>         /* XC8 General Include File */
#include <stdint.h>        /* For uint8_t definition */
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>       /* For true/false definition */
#include <htc.h>
#include "I2C.h"

#endif

[B]I2C.h[/B]
#ifndef __I2C_H
#define __I2C_H

// Define i2c pins
#define SDA			GP4				// Data pin for i2c
#define SCK			GP5				// Clock pin for i2c
#define SDA_DIR		TRISIO4			// Data pin direction
#define SCK_DIR		TRISIO5			// Clock pin direction

#define DataPinADCMask		ANS3	// It is attached on GP4(AN3) pin
#define ClockPinADCMask		ANS3	// It is not attached on any ADC pin

// Define i2c speed
#define I2C_SPEED	1				// kbps
#define HalfBitDelay 500/I2C_SPEED	// usec

// Define macros
#define Set_SDA_Low		SDA_DIR = 0
#define Set_SDA_High	SDA_DIR = 1
#define Set_SCK_Low		SCK_DIR = 0
#define Set_SCK_High	SCK_DIR = 1

//Function Declarations
void InitI2C(void);
void I2C_Start(void);
void I2C_ReStart(void);
void I2C_Stop(void);
void I2C_Send_ACK(void);
void I2C_Send_NACK(void);
bit  I2C_Write_Byte(unsigned char);
unsigned char I2C_Read_Byte(void);

#endif

[B]I2C.c[/B]
#include "Includes.h"



// Function Purpose: Set initial values of SCK and SDA pins
void InitI2C(void)
{
	DataPinADCMask  = 1;	// Make analog output
	ClockPinADCMask = 1;	// Make analog output

	// Make SDA and SCK pins input initially
	SDA_DIR = 1;
	SCK_DIR = 1;

	// Write zero in output register of SDA and SCK pin
	SDA = 0;
	SCK = 0;
}


// Function Purpose: I2C_Start sends start bit sequence
void I2C_Start(void)
{
	SDA = 0;	// Write zero in output register
	SCK = 0;	// of SDA and SCK pin

	Set_SCK_High;				// Make SCK pin high
	Set_SDA_High;				// Make SDA pin High
	__delay_us(HalfBitDelay);	// Half bit delay
	Set_SDA_Low;				// Make SDA Low
	__delay_us(HalfBitDelay);	// Half bit delay
}


// Function Purpose: I2C_ReStart sends start bit sequence
void I2C_ReStart(void)
{
	Set_SCK_Low;				// Make SCK pin low

	__delay_us(HalfBitDelay/2);	// Data pin should change it's value,
								// when it is confirm that SCK is low
	Set_SDA_High;				// Make SDA pin High

	__delay_us(HalfBitDelay/2);	// 1/4 bit delay
	Set_SCK_High;				// Make SCK pin high
	__delay_us(HalfBitDelay/2);	// 1/4 bit delay
	Set_SDA_Low;				// Make SDA Low
	__delay_us(HalfBitDelay/2);	// 1/4 bit delay
}


//Function : I2C_Stop sends stop bit sequence
void I2C_Stop(void)
{
	Set_SCK_Low;				// Make SCK pin low

	__delay_us(HalfBitDelay/2);	// Data pin should change it's value,
								// when it is confirm that SCK is low
	Set_SDA_Low;				// Make SDA pin low

	__delay_us(HalfBitDelay/2);	// 1/4 bit delay
	Set_SCK_High;				// Make SCK pin high
	__delay_us(HalfBitDelay/2);	// 1/4 bit delay
	Set_SDA_High;				// Make SDA high
	__delay_us(HalfBitDelay/2);	// 1/4 bit delay
}



//Function : I2C_Send_ACK sends ACK bit sequence
void I2C_Send_ACK(void)
{
	Set_SCK_Low;				// Make SCK pin low
	__delay_us(HalfBitDelay/2);	// Data pin should change it's value,
								// when it is confirm that SCK is low
	Set_SDA_Low;				// Make SDA Low
	__delay_us(HalfBitDelay/2);	// 1/4 bit delay
	Set_SCK_High;				// Make SCK pin high
	__delay_us(HalfBitDelay);	// Half bit delay
}


//Function : I2C_Send_NACK sends NACK bit sequence
void I2C_Send_NACK(void)
{
	Set_SCK_Low;				// Make SCK pin low
	__delay_us(HalfBitDelay/2);	// Data pin should change it's value,
								// when it is confirm that SCK is low
	Set_SDA_High;				// Make SDA high
	__delay_us(HalfBitDelay/2);	// 1/4 bit delay
	Set_SCK_High;				// Make SCK pin high
	__delay_us(HalfBitDelay);	// Half bit delay
}


// Function Purpose: I2C_Write_Byte transfers one byte
bit I2C_Write_Byte(unsigned char Byte)
{
	static bit ACK = 0;

	unsigned char i;		// Variable to be used in for loop

	for(i=0;i<8;i++)		// Repeat for every bit
	{
		Set_SCK_Low;		// Make SCK pin low

		__delay_us(HalfBitDelay/2);	// Data pin should change it's value,
									// when it is confirm that SCK is low

		if((Byte<<i)&0x80)  // Place data bit value on SDA pin
			Set_SDA_High;	// If bit is high, make SDA high
		else				// Data is transferred MSB first
			Set_SDA_Low;	// If bit is low, make SDA low

		__delay_us(HalfBitDelay/2);	// Toggle SCK pin
		Set_SCK_High;				// So that slave can
		__delay_us(HalfBitDelay);	// latch data bit
    }

	// Get ACK from slave
	Set_SCK_Low;
    Set_SDA_High;
    __delay_us(HalfBitDelay);
    Set_SCK_High;
    __delay_us(HalfBitDelay);

	DataPinADCMask = 0;		// Make digital input
	ACK = SDA;				// Read data pin status
	DataPinADCMask = 1;		// Make analog output

	return ACK;
}


// Function Purpose: I2C_Read_Byte reads one byte
unsigned char I2C_Read_Byte(void)
{
	unsigned char i, RxData = 0;

	for(i=0;i<8;i++)
	{
		Set_SCK_Low;					// Make SCK pin low
		Set_SDA_High;					// Don't drive SDA
		__delay_us(HalfBitDelay);		// Half bit delay
		Set_SCK_High;					// Make SCK pin high
		__delay_us(HalfBitDelay/2);		// 1/4 bit delay
		DataPinADCMask = 0;				// Make digital input
		RxData = RxData|(SDA<<(7-i));	// Captured received bit
		DataPinADCMask = 1;				// Make analog output
		__delay_us(HalfBitDelay/2);		// 1/4 bit delay
	}

    return RxData;						// Return received byte
}

[B]main.c[/B]
#include "Includes.h"


// CONFIG
#pragma config FOSC = INTOSCIO  // Oscillator Selection bits (INTOSCIO oscillator: I/O function on RA4/OSC2/CLKOUT pin, I/O function on RA5/OSC1/CLKIN)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = ON       // Power-up Timer Enable bit (PWRT enabled)
#pragma config MCLRE = OFF      // MCLR Pin Function Select bit (MCLR pin function is digital input, MCLR internally tied to VDD)
#pragma config CP = OFF         // Code Protection bit (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Code Protection bit (Data memory code protection is disabled)
#pragma config BOREN = ON       // Brown Out Detect (BOR enabled)
#pragma config IESO = ON        // Internal External Switchover bit (Internal External Switchover mode is enabled)
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enabled bit (Fail-Safe Clock Monitor is enabled)

void InitCCT(void)
{
	ANSEL  = 0x00;       // Set ports as digital I/O, not analog input
	ADCON0 = 0x00;		 // Shut off the A/D Converter
	CMCON0 = 0x07;		 // Shut off the Comparator
	VRCON  = 0x00;	     // Shut off the Voltage Reference
        TRISIO = 0x00;       // GP3 input, rest all output
	GPIO   = 0x00;       // Make all pins 0
}

int main(int argc, char** argv) {
        unsigned char msb;
        unsigned char lsb;

	InitCCT();	// Turn off ADC and comparator to make pins digital IOs
	InitI2C();	// Initialize i2c pins

        __delay_ms(100);
						// Send stop bit on i2c
        I2C_Start();				// Send start bit on i2c
        I2C_Write_Byte((unsigned char)0x18 & 0xFE);
        I2C_Write_Byte((unsigned char)0x05);
        I2C_Start();
        I2C_Write_Byte((unsigned char)0x18 | 0x01);		// Send 0xA0 on i2c
        msb = I2C_Read_Byte();	// Read value from i2c
        I2C_Send_ACK();  // Send ACK bit on i2c
        lsb = I2C_Read_Byte();	// Read value from i2c
        I2C_Send_NACK();  // Send ACK bit on i2c
        I2C_Stop();
        eeprom_write(0x00, msb);
        eeprom_write(0x01, lsb);
        while(1){
        }
}

msb and lsb are always 0x00, I really can not find the problem, hope someone can help.
thanks

 

[milan.rajik]

Here is an Arduino code.

https://learn.adafruit.com/adafruit-mcp9808-precision-i2c-temperature-sensor-guide/wiring

 

[ud23]

https://ww1.microchip.com/downloads/en/DeviceDoc/25095A.pdf

read the page number #43 at above link sample code is given for pic controller modify it according to your PIC controller.