Shift in Bluetooth

Normally when a communication technology is evolving it will try to increase its transmission rate. So the Bluetooth technology was also evolving similarly and the main evolutions are:

1. First one was Basic Rate (BR) (the name came after the evolution into second one). It was having a physical layer with 1 Mbps.
2. Secondly the Enhanced Data Rate(EDR) i.e. V.2.0 which increased the data rate upto 3Mbps.
3. Then introduced an Alternative MAC PHY layer (AMP) on V.3.0 which eventually given a speed of about 54Mbps.

There needed a technology which uses much lesser power for prolonged use. Even though other low power RF wireless technologies were there, they were not having a unique encrypted protocol for communication. These made the researchers to think of making the Bluetooth Low Energy V4.0(BLE) protocol which is a cheaper low power protocol compared to older Bluetooth technology. For that they sacrificed the transmission rate but maintaining or improving other parameters. They reduced the transmission data rate to about 0.3Mbps which works under extreme low power. Today more BLE products are coming to market as Bluetooth Smart devices which needed lesser energy!

PIC16F877A I2C code Interfacing Library

Summary Of PIC16F877A:
======================
PIC16F877A is an 8 bit RISC microcontroller developed by Microchip. Only 35 assembly instructions are there for the microcontroller which makes it a better RISC controller with full functionalities.
The specifications are:

• 20MHz maximum frequency.

• 14.3KB of program memory.(can hold upto 8192 single word instructions)

• 368 Bytes SRAM.

• 256 EEPROM

• 33 multiplexed I/O pins.

• Eight 10 bit ADC channels.

• 2 PWM.

• 1 SPI & 1 I2C (MSSP works as either one at a time)

• 1 USART

• Two 8-bit timers & one 16-bit timer.

• 2 Comparators 

What to Know before programming :

• Uses MSSP(Master synchronous serial port) module.

• Mode Supported

• Master Mode

• Multimaster mode

• Slave mode

• Addressing Supported

• 7 - bit

• 10 - bit

• Registers used:

• MSSP Control Register (SSPCON)

• MSSP Control Register 2 (SSPCON2)

• MSSP Status Register (SSPSTAT)

• Serial Receive/Transmit Buffer Register(SSPBUF)

• MSSP Shift Register (SSPSR) – Not directly accessible

• MSSP Address Register (SSPADD)

• slave mode - slave address

• master mode - lower 7 bits acts as baud rate generator reload value.

Summary to develop code:
======================
You can use MPLAB IDE for the development. Assembly programming can be done using the IDE, but c coding requires additional compilers like MPLAB C and HI-TECH compilers. Now Microchip integrated the above two and made a new compiler named as MPLAB XC Compiler. There the free compiler is having lesser optimization (Only 25% compared to the PRO paid version). Means the level of code compression(which requires lesser ROM space) and accurate delay may have the difference. 

Master mode coding:

===========================
Please add i2c.c file in your c file containing the main function and use the code.

i2c.h
=======

void i2c_init();
void i2c_waitForIdle();
void i2c_start();
void i2c_repStart();
void i2c_stop();
unsigned char i2c_read( unsigned char ack);
unsigned char i2c_write( unsigned char i2cWriteData);

i2c.c
=====

/*
PIC16F877A Code for i2c in master mode.
Developed By Arun Chettoor
Can be used freely in any project under GPL license.
E-mail : arunkrishnanc@gmail.com
*/


#include"i2c.h"

#define clockFreq 10 //in MHz
#define i2cClock 0 // 0 for 100KHz and 1 for 400KHz

void i2c_init(){
char i2cFreq;
TRISC3=1;           // set SCL and SDA pins as inputs
  TRISC4=1;

  SSPCON = 0x38;      // set I2C master mode
  SSPCON2 = 0x00;

  #if i2cClock==0
  i2cFreq=100;
  #else
  i2cFreq=400;
  #endif

  SSPADD = (char)(((clockFreq*1000)/i2cFreq)-1);

  PSPIF=0;      // clear SSPIF interrupt flag
  BCLIF=0;      // clear bus collision flag
}

/*********************************************
To wait until i2c is idle.
*********************************************/

void i2c_waitForIdle()
{
 while (( SSPCON2 & 0x1F ) | STAT_RW ) {}; // wait for idle and not writing
}

/********************************************
To sent the start sequence
**********************************************/

void i2c_start()
{
 i2c_waitForIdle();
 SEN=1;
}

/*********************************************
To sent a repeated start sequence
*********************************************/

void i2c_repStart()
{
 i2c_waitForIdle();
 RSEN=1;
}

/*********************************************
To sent a stop sequence
**********************************************/

void i2c_stop()
{
 i2c_waitForIdle();
 PEN=1;
}

/*********************************************
Read char from i2c buffer register and return the value
*********************************************/

unsigned char i2c_read( unsigned char ack )
{
 unsigned char i2cReadData;

 i2c_waitForIdle();

 RCEN=1;

 i2c_waitForIdle();

 i2cReadData = SSPBUF;

 i2c_waitForIdle();

 if ( ack )
  {
  ACKDT=0;
  }
 else
  {
  ACKDT=1;
  }
  ACKEN=1;               // send acknowledge sequence

 return( i2cReadData );
}

/*********************************************
Write char data to i2c buffer

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

unsigned char i2c_write( unsigned char i2cWriteData )
{
 i2c_waitForIdle();
 SSPBUF = i2cWriteData;
 i2c_waitForIdle();
 return ( ! ACKSTAT  ); // function returns '1' if transmission is acknowledged
}