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

	Calibrate.c

	Martin Newell, 2005, San Jose, California
	Version 1, June 18, 2005

	Calibrate PIC chips
	
	This is primarily for the PIC12F635 and 683 since they appear to need calibration,
		but can be used to recalibrate 12F629 and 675 which have calibration values
		that can be overwritten using a checkbox in Winpic's Options
		
	Pins 5,6,7 are toggled every 1 mS, for measuring on an oscilloscope
	Pins 2,3 are toggled every 0.25 second, for measuring with a stopwatch and
		an LED or analog voltmeter
	
	To calibrate a chip:

	Oscilloscope
	1. Measure the period, P, of the rising edgeof pin 5,6 or 7 in microseconds.
		Should be about 2000 microseconds
	2. Replace the return value from GetOsccal() with R + (P - 2000)/20, where R is
		 the current return value.  5 bit 2s complement arithmetic.
	3. Repeat from 1 until P = 2000 uS

	Stop watch and LED or analog voltmeter
	1. Measure how many seconds, S, it takes for pin 2 or 3 to turn on 100 times.
		Should be about 50 seconds
	2. Replace the return value from GetOsccal() with R + (S - 50)*2, where R is
		 the current return value.  5 bit 2s complement arithmetic.
	3. Repeat from 1 until S = 50 seconds

	The calibration value can be changed in the programmer code buffer and the program 
		reloaded and tested without recompiling.


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

//#define PIC12F629
#define PIC12F635
//#define PIC12F675
//#define PIC12F683

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

#ifdef PIC12F629
#pragma config = 0x3F84 
#endif // PIC12F635

#ifdef PIC12F635
#pragma config = 0x33C4 
#pragma bit	IRCF0	@ OSCCON.4					// definitions missing from PIC12F635.h
#pragma bit	IRCF1	@ OSCCON.5
#pragma bit	IRCF2	@ OSCCON.6
#endif

#ifdef PIC12F675
#pragma config = 0x3F84 
#define HAS_AD
#endif // PIC12F635

#ifdef PIC12F683
#pragma config = 0x33C4 
#pragma bit	IRCF0	@ OSCCON.4					// definitions missing from PIC12F635.h
#pragma bit	IRCF1	@ OSCCON.5
#pragma bit	IRCF2	@ OSCCON.6
#define HAS_AD
#endif

// Chip Configuration parameters
// Oscillator Internal
// Watchdog Off
// Power Up Timer On
// MCLR Internal
// Brown Out Off
// Code Protect Off
// Data EE Read Protect Off

char GetOsccal();

/************************************** MAIN **************************************/

void main() {
	char i,j;
	char t;

#ifdef PIC12F629
	OSCCAL = GetOsccal();						// Set oscillator calibration
#endif // PIC12F635

#ifdef PIC12F635
	IRCF0 = 0; IRCF1 = 1; IRCF2 = 1;			// Select 4MHz
	OSCTUNE = GetOsccal();
#endif

#ifdef PIC12F675
	OSCCAL = GetOsccal();						// Set oscillator calibration
#endif // PIC12F635

#ifdef PIC12F683
	IRCF0 = 0; IRCF1 = 1; IRCF2 = 1;			// Select 4MHz
	OSCTUNE = GetOsccal();
#endif

	TRISIO = 8;  								// Input on GP3. 0 = Output, 1 = Input
	OPTION = 8;									// Assign prescaler to WDT, so TMR0 clock is 1:1
    CM2 = 1; CM1 = 1; CM0 = 1;					//These turn the input pins back to digital I/O

#ifdef HAS_AD
	ANSEL = 0; 									//Turn off ADC
#endif

#pragma update_RP 0

    GPIO = 0x00;

#define COUNT1 250
#define COUNT2 197
	// Following inner loop takes T2 = 15 + COUNT2*5 = 1000 i.e. 2 mS per cycle 
	// Outer loop takes	T1 = T2 * COUNT1 = 250 mS i.e. 2 on-off cycles per second

#asm


a001	MOVLW COUNT1
		MOVWF i
		GOTO a002

b001	NOP
		NOP
		NOP
		NOP
		NOP
		NOP
		NOP
a002	NOP
		NOP
		MOVLW COUNT2
		MOVWF j
b002	NOP
		NOP
		DECFSZ j,1
		GOTO  b002

		MOVLW .7
		XORWF GPIO,1	; Toggle pins 5,6,7 every 1 mS

		DECFSZ i,1
		GOTO  b001

		MOVLW .48
		XORWF GPIO,1	; Toggle pins 2,3 every 0.25 second

		GOTO  a001
#endasm
    
} // main

/************************************** GetOsccal **************************************/

#ifdef PIC12F683
#pragma origin 0x7FF
#else
#pragma origin 0x3FF
#endif
// This is to enable us to create a call to the oscillator calibration value in 12F629
// On 12F629 this is a dummy - actual procedure is preset in chip and will normally override
// On 12F635 this procedure runs and returns value shown - need to calibrate manually
// OSCCAL is 5 bit, 2's complement, i.e. -16 to +15, or 0x10 to 0xF
// A change of +1 causes about a +1% change in speed (i.e. reduction in cycle time)
// No need to recompile to change value - can set the value in WinPic's buffer and rewrite the PIC
// Can overwrite calibration on 12F629 by checking box in Options panel of WinPic
char GetOsccal() {return 0x00;}

/***************************************** End *****************************************/