I2C Bit-Bangging - MSP430

i2c_sw.c

/********************************************************************************
Module		: I2C_SW
Author		: 05/04/2015, by KienLTb - https://kienltb.wordpress.com/
Description	: I2C software using bit-banging.


********************************************************************************/

/*-----------------------------------------------------------------------------*/
/* Header inclusions */
/*-----------------------------------------------------------------------------*/
#include "msp430g2553.h"
#include "i2c_sw.h"

/*-----------------------------------------------------------------------------*/
/* Local Macro definitions */
/*-----------------------------------------------------------------------------*/

/*-----------------------------------------------------------------------------*/
/* Function prototypes */
/*-----------------------------------------------------------------------------*/
unsigned char Read_SCL(void);
unsigned char Read_SDA(void);
void Clear_SCL(void);
void Clear_SDA(void);

void I2C_Init(void);
void I2C_Start(void);
void I2C_Stop(void);

void I2C_Writebit(unsigned char bit);
unsigned char I2C_ReadByte(void);

void I2C_WriteByte(unsigned char Data);
unsigned char I2C_ReadByte(void);

void I2C_WriteData(unsigned char *Data, unsigned char DevideAddr, unsigned char Register, unsigned char nLength);
void I2C_ReadData(unsigned char *Buff, unsigned char DevideAddr, unsigned char Register, unsigned char nLength);

/*-----------------------------------------------------------------------------*/
/* Function implementations */
/*-----------------------------------------------------------------------------*/


/*--------------------------------------------------------------------------------
Function	: Read_SCL
Purpose		: Set SCL as input and return current Logic level of SCL (0 or 1)
			  nomal is 1 because pullup by resistor
Parameters	: None
Return		: Logic level of SCL pin
--------------------------------------------------------------------------------*/
unsigned char Read_SCL(void)
{
	I2C_PxDIR  &= ~SCL;
	return((I2C_PxIN & SCL) != 0);

}
/*--------------------------------------------------------------------------------
Function	: Read_SDA
Purpose		: Set SDA as input and return current Logic level of SDA (0 or 1),
			  nomal is 1 because pullup by resistor
Parameters	: None
Return		: Logic level of SDA pin
--------------------------------------------------------------------------------*/
unsigned char Read_SDA(void)
{
	I2C_PxDIR  &= ~SDA;
	return((I2C_PxIN & SDA) != 0);
}

/*--------------------------------------------------------------------------------
Function	: Clear_SCL
Purpose		: Set SCL as Out put, logic Low
Parameters	: None
Return		: None
--------------------------------------------------------------------------------*/
void Clear_SCL(void)
{
	I2C_PxDIR  |= SCL;
}
/*--------------------------------------------------------------------------------
Function	: Clear_SDA
Purpose		: Set SDA as Out put, logic LOW
Parameters	: None
Return		: None
--------------------------------------------------------------------------------*/
void Clear_SDA(void)
{
	I2C_PxDIR  |= SDA;
}
/*--------------------------------------------------------------------------------
Function	: I2C_Init
Purpose		: Initialize I2C block
Parameters	: None
Return		: None
--------------------------------------------------------------------------------*/
void I2C_Init(void)
{
	// Conffig SCL and SDA as GPIO
  	I2C_PxSEL   &= ~(SCL + SDA);
	I2C_PxSEL2  &= ~(SCL + SDA);
	// Set SCL and SDA is logic HIGH
	I2C_PxDIR   &= ~(SCL + SDA);
	I2C_PxOUT  	&= ~(SCL + SDA);
}
/*--------------------------------------------------------------------------------
Function	: I2C_Start
Purpose		: Send start signal
Parameters	: None
Return		: None
--------------------------------------------------------------------------------*/
void I2C_Start(void)
{
	Read_SDA();				//set SDA to 1
	I2C_DELAY();
	Clear_SDA();			//set SDA to 0, currently SCL is 1
	I2C_DELAY();
	Clear_SCL();			//set SCL to 0
}
/*--------------------------------------------------------------------------------
Function	: I2C_Stop
Purpose		: Send Stop signal
Parameters	: None
Return		: None
--------------------------------------------------------------------------------*/
void I2C_Stop(void)
{
	Clear_SDA();			//set SDA to 0
	I2C_DELAY();
	Read_SCL();				//set SCL to 1
	I2C_DELAY();
	Read_SDA();				//set SDA to 1
}
/*--------------------------------------------------------------------------------
Function	: I2C_Writebit
Purpose		: Write bit to I2C bus
Parameters	: a bit need to write
Return		: None
--------------------------------------------------------------------------------*/
void I2C_Writebit(unsigned char bit)
{
	if(bit)
	  Read_SDA();
	else
	  Clear_SDA();
	I2C_DELAY();
	Read_SCL();
	I2C_DELAY();
	Clear_SCL();
}
/*--------------------------------------------------------------------------------
Function	: I2C_Readbit
Purpose		: Read bit to I2C bus
Parameters	: None
Return		: unsigned char
--------------------------------------------------------------------------------*/
unsigned char I2C_Readbit(void)
{
	unsigned char bit;
	//Let the slave driver data
	Read_SDA();
	I2C_DELAY();
	Read_SCL();
	bit = Read_SDA();
	I2C_DELAY();
	Clear_SCL();
	return bit;
}
/*--------------------------------------------------------------------------------
Function	: I2C_WriteByte
Purpose		: Write a Byte to I2C bus
Parameters	: unsigned char Data
Return		: None
--------------------------------------------------------------------------------*/
void I2C_WriteByte(unsigned char Data)
{
  	unsigned char nBit;

	for(nBit = 0; nBit < 8; nBit++)
	{
		I2C_Writebit((Data & 0x80) != 0);
		Data <<= 1;
	}
	I2C_Readbit(); // Waite NACK
}
/*--------------------------------------------------------------------------------
Function	: I2C_ReadByte
Purpose		: Read a Byte to I2C bus
Parameters	: None
Return		: unsigned char
--------------------------------------------------------------------------------*/
unsigned char I2C_ReadByte(void)
{
	unsigned char Buff = 0;
	unsigned char nBit;
	
	for(nBit = 0; nBit < 8; nBit++)
	{
		Buff = (Buff << 1) | I2C_Readbit();
	}
	return Buff;
}
/*--------------------------------------------------------------------------------
Function	: I2C_WriteData
Purpose		: Write n Byte to I2C bus
Parameters	: Data 			- Pointer to Data need to write
			  DevideAddr	- Devide Address
			  Register		- Register Address
			  nLength		- Number of Byte need to write
Return		: None
--------------------------------------------------------------------------------*/
void I2C_WriteData(unsigned char *Data, unsigned char DevideAddr, unsigned char Register, unsigned char nLength)
{
	unsigned char nIndex;
  	I2C_Start();
	I2C_WriteByte(DevideAddr << 1);  // byDeviceAddr is 7 bit and command is write
	I2C_WriteByte(Register);
	for(nIndex = 0; nIndex < nLength; nIndex++)
	{
		I2C_WriteByte(*(Data + nIndex));
	}
	I2C_Readbit();
	I2C_Stop();
}
/*--------------------------------------------------------------------------------
Function	: I2C_ReadData
Purpose		: Read n Byte from I2C bus
Parameters	: Buff 			- Pointer to Buffer store value
			  DevideAddr	- Devide Address
			  Register		- Register Address
			  nLength		- Number of Byte need to read
Return		: None
--------------------------------------------------------------------------------*/
void I2C_ReadData(unsigned char *Buff, unsigned char DevideAddr, unsigned char Register, unsigned char nLength)
{
	unsigned char nIndex;
  	I2C_Start();
	I2C_WriteByte(DevideAddr << 1);
	I2C_WriteByte(Register);
	I2C_Stop();
	_NOP(); 								// Short delay
	I2C_Start();
	_NOP();									// Short delay
	I2C_WriteByte((DevideAddr << 1) | 1);
	for(nIndex = 0; nIndex < nLength; nIndex++)
	{
		*(Buff + nIndex) = I2C_ReadByte();
			if(nIndex > 0)I2C_Writebit(ACK);
	}
	I2C_Writebit(NACK);
	I2C_Stop();
}

i2c_sw.h

/********************************************************************************
Module		: I2C_SW
Author		: 05/04/2015, by KienLTb - https://kienltb.wordpress.com/
Description	: I2C software using bit-banging.

********************************************************************************/
#ifndef _I2C_SW_H_
#define _I2C_SW_H_
/*-----------------------------------------------------------------------------*/
/* Macro definitions  */
/*-----------------------------------------------------------------------------*/

/*-----------------------------------------------------------------------------*/
/* Local Macro definitions */
/*-----------------------------------------------------------------------------*/
#define I2C_PxSEL		P1SEL
#define I2C_PxSEL2		P1SEL2
#define I2C_PxDIR		P1DIR
#define I2C_PxOUT		P1OUT
#define I2C_PxIN		P1IN

#define SCL        		BIT6
#define SDA         	BIT7

#define ACK 			0x00
#define NACK			0x01

#define TIME_DELAY 100
#define I2C_DELAY() __delay_cycles(TIME_DELAY)
/*-----------------------------------------------------------------------------*/
/* Function prototypes  */
/*-----------------------------------------------------------------------------*/

//NOTE: Need custom Read_SCL(), Read_SDA(), Clear_SCL(), Clear_SDA() to compatible Hardware.

unsigned char Read_SCL(void); // Set SCL as input and return current level of line, 0 or 1, nomal is 1 because pullup by res
unsigned char Read_SDA(void); // Set SDA as input and return current level of line, 0 or 1, nomal is 0 because pull by res

void Clear_SCL(void); // Actively drive SCL signal Low
void Clear_SDA(void); // Actively drive SDA signal Low

void I2C_Init(void);
void I2C_Start(void);
void I2C_Stop(void);

void I2C_Writebit(unsigned char bit);
unsigned char I2C_Readbit(void);

void I2C_WriteByte(unsigned char Data);
unsigned char I2C_ReadByte(void);

void I2C_WriteData(unsigned char *Data, unsigned char DevideAddr, unsigned char Register, unsigned char nLength);
void I2C_ReadData(unsigned char *Buff, unsigned char DevideAddr, unsigned char Register, unsigned char nLength);

#endif // _I2C_SW_H_

https://gist.github.com/ksvbka/fec1f28ce40c276334fb#file-i2c_sw-c-L222

Additional call of I2C_Readbit on the line 222 is causing issues on some I2C devices such as EEPROM (I wasn't able to write anything into the EEPROM until I've removed this line).
I2C_Readbit is called in the I2C_WriteByte function and doesn't need to be called again...

https://gist.github.com/ksvbka/fec1f28ce40c276334fb#file-i2c_sw-c-L248

Multibyte read also fails on the I2C EEPROM. This like should look like this:
if(nIndex < nLength - 1) I2C_Writebit(ACK);