Basic demo of using the I2C library.

I2CBasics.c

/////////////////////////////////////////////////////////////////////////////
// HC12 Program:  I2C Demo
// Processor:     MC9S12XDP512
// Bus Speed:     20 MHz (Requires Active PLL)
// Author:        AJ Armstrong
// Details:       Demonstration of the I2C Driver Libraries
// Date:          Dec 2023
// Revision History :
/////////////////////////////////////////////////////////////////////////////

#include <stdio.h>      // For sprintf, etc
#include <ctype.h>      // For character utilities
#include <string.h>     // Various string utilities
#include <hidef.h>      // Common defines and macros
#include "derivative.h" // Derivative-specific definitions
#include "pll.h"        // Phase-locked loop clock control
#include "swled.h"      // GPIO switches and LEDs
#include "segs.h"       // 7-Segment Displays
#include "timer.h"      // Enhanced capture timer
#include "portj.h"      // Interrupt buttons
#include "pit.h"        // Periodic Interrupt timer
#include "rti.h"        // Realtime interrupts
#include "lcd.h"        // LCD Display
#include "sci.h"        // Serial communications interface (EIA/TIA-232)
#include "i2c.h"        // Carlos Estay's I2C Driver Libraries

/////////////////////////////////////////////////////////////////////////////
// Local Prototypes
/////////////////////////////////////////////////////////////////////////////


/////////////////////////////////////////////////////////////////////////////
// Global Variables
/////////////////////////////////////////////////////////////////////////////


/////////////////////////////////////////////////////////////////////////////
// Constants
/////////////////////////////////////////////////////////////////////////////

/////////////////////////////////////////////////////////////////////////////
// Main Entry
/////////////////////////////////////////////////////////////////////////////

void main(void)
{
  // Variables
  int test = 0; // For capturing return values
  char reg = 0; // For capturing single byte results
  RTC_Read clockTime; // Type for getting RTC data (see i2c.h)

  /////////////////////////////////////////////////////////////////////////////
  // One-Time Initializations
  /////////////////////////////////////////////////////////////////////////////
  _DISABLE_COP();        // No watchdog
  PLL_To20MHz();                         // Configure the main clock to 20 MHz (implications for timers)
  SWL_Init();                            // Standard initialization for switches and LEDs
  SEG_Init();                            // Standard initializaton for 7-seg displays
  RTI_Init();                            // Initialize RTI timer

  /////////////////////////////////////////////////////////////////////////////
  // Main Program Loop
  /////////////////////////////////////////////////////////////////////////////

  EnableInterrupts; // Ensure our board will respond to interrupt signals.
  LCD_Init(); // Current LCD drivers need RTI and interrupts. //FIXME
  LCD_StringRC(0,6,"I2C Demo");
  LCD_StringRC(1,6,"--------");  

  // This demo will use the M41T81S already built into our board and attached
  // at address 0x68 (RTC_ADD in header)

  // First, initialize the I2C at fast (400 kbps) speed
  I2C0_InitBus(I2CBus400);

  // Test for STOP flag by trying to read SECONDS 
  // register from the RTC. If the special bit
  // 0x80 (STOP, RTC_SECONDS_ST) is set in the return,
  // then is not running.
  test = I2C0_RegRead(&reg, RTC_ADD, RTC_SECONDS);
  if (reg & RTC_SECONDS_ST) // Stopped
  { 
    //Yellow LED means it was stopped.
    SWL_SetLEDs(eYellow);
    //Ok. Let's start it by rewriting the value with
    //the stop bit reset
    I2C0_RegWrite(RTC_ADD, RTC_SECONDS, reg & ~RTC_SECONDS_ST, IIC0_STOP);
  }


  //Also, if it was halted, that shows up in the AlarmHour register
  //as the special bit 0x40 (RTC_AL_HOUR_HT)
  //This is probably because the board was shut off or had a power
  //failure.
  test = I2C0_RegRead(&reg, RTC_ADD, RTC_AL_HOUR);
  if (reg & RTC_AL_HOUR_HT) // Halted
  { 
    //Red LED means it was halted.
    SWL_SetLEDs(eRed);
    //Throw the seconds register onto the upper right 7Segs
    //to show the seconds currently stored (time of failure)
    test = I2C0_RegRead(&reg, RTC_ADD, RTC_SECONDS);
    SEG_8H(2,reg); //Hex because seconds is BCD on timer

    // Throw the minutes recorded for the halt to upper left 7segs
    test = I2C0_RegRead(&reg, RTC_ADD, RTC_MINUTES);
    SEG_8D(0,reg & 0x0F); //Decimal and mask because...well, look at datasheet

    //Unhalt it by rewriting the value with the  bit reset
    I2C0_RegWrite(RTC_ADD, RTC_AL_HOUR, reg & ~RTC_AL_HOUR_HT, IIC0_STOP);

    //IS THIS NOT BETTER THAN FLASHING 1200?
  }

  for (;;)
  {
    //Show the current minutes/seconds from the RTC on the lower segs
    if(rtiCount % 250)
    {
      test = I2C0_RegRead(&reg, RTC_ADD, RTC_SECONDS);
      SEG_8H(6,reg); //Hex because RTC seconds is BCD
      test = I2C0_RegRead(&reg, RTC_ADD, RTC_MINUTES);
      SEG_8D(4,reg & 0x0F); //Decimal and mask because...well, look at datasheet
    }
    asm WAI;
  }
}
/////////////////////////////////////////////////////////////////////////////
// Functions
/////////////////////////////////////////////////////////////////////////////



/////////////////////////////////////////////////////////////////////////////
// Interrupt Service Routines
/////////////////////////////////////////////////////////////////////////////