u08adc.c

MC68HC08JB8 的USB驱动源程序,开发环境是Code wayyior HC08

//============================================================================
// File: U08ADC.C
// Func: Software ADC for USB08
// Ver.: 1.01
// Auth: (C)2000,2001 by Oliver Thamm, MCT Elektronikladen GbR
//       http://hc08web.de/usb08
// Rem.: View/Edit this File with TAB-Size=4
// Jan 02 : Adapted for CodeWarrior by Isabelle GIRAUD, Metrowerks Europe 
//============================================================================

#include "hc08jb8.h"
#include "u08adc.h"

#define _CHAR_ADR(x)  ((volatile unsigned char*)&(x))
#define _COPY_BYTE(from, to, offset) (*(_CHAR_ADR(to)+(offset))=*(_CHAR_ADR(from)+(offset)))
#define _COPY_16_BITS_HIGH_FIRST(from, to) (_COPY_BYTE(from, to,0),_COPY_BYTE(from, to,1))

//----------------------------------------------------------------------------

void initSADC() {

	// disable internal Pull-Ups on PTE
	POCR &= ~0x80;	// disable PTE20P
	}

//----------------------------------------------------------------------------

unsigned scaleSADC(unsigned t1, unsigned t2) {

	unsigned retval;
	unsigned char n;

	//-----------------------------------------------------------
	// retval = (t2/t1) * 256  (0 <= retval <= 0xff)
	// We are taking care of overflow/accuracy by actually doing:
	// retval = (t2 * 2^j) / (t1 / 2^k)
	// with j+k = 8 (because 2^8=256) 
	//-----------------------------------------------------------
	for(n=0; n<8; n++) {
		if((t2 & 0x8000) == 0) t2 <<= 1;
		else t1 >>= 1;
		}
	retval = t2/t1;
	retval *= 135;	// *135/128 = *1.055
	retval >>= 7;
	if(retval > 0x00ff) retval = 0x00ff;
	return(retval);
	}

//----------------------------------------------------------------------------

void delay025ms(void) {
	asm {
		LDA #240
		 __l_01: DBNZA  __l_01
		}// 3cyc x 333ns x 240+9 = 0,249ms
	}

//----------------------------------------------------------------------------

unsigned char getSADC(char channel) {
	unsigned int tcal, tcal0, tcal1;
	unsigned int tacq, tacq0, tacq1;
	unsigned int t;

	// convert channel # 1/2/3 to 0x01/0x02/0x04
	if(channel == 3) channel++;

	PTD &= ~0x78;		// all PTD[3..6] = L
	PTE |= 0x07;		// all PTE[0..2] = H;

	// *** calibration cycle ***

	DDRD |= 0x78;		// Output L on PTD[3..6]
	DDRE |= 0x07;		// Output H on PTE[0..2]
	delay025ms();		// discharge C13..C15

	DDRE &= ~0x07;		// PTE[0..2] HiZ (PTE[0..2] configured as Input)
	TSC |= 0x10  ;  // reset Tim counter
	
  _COPY_16_BITS_HIGH_FIRST(TCNTH,tcal0);
  
	while((PTE & channel) != 0) ; // while the threshold level is not reached ....
	
	_COPY_16_BITS_HIGH_FIRST(TCNTH,tcal1);// cal end time

	tcal = tcal1 - tcal0;

	// *** acquisition cycle ***
	DDRD &= ~0x38;	// PTD[3..5] = HiZ, PTD[6] = L
	DDRE |= 0x07;		// Output H on PTE[0..2]
	delay025ms();		// discharge C13..C15

	DDRE &= ~0x07;		// PTE HiZ (Input)
  TSC |= 0x10  ;  // reset Tim counter
  
  
	 _COPY_16_BITS_HIGH_FIRST(TCNTH,tacq0);// acq start time

	while((PTE & channel) != 0) ;  // while the threshold level is not reached ....
 	 _COPY_16_BITS_HIGH_FIRST(TCNTH,tacq1);// acq end time
   
	tacq = tacq1 - tacq0;

	if(tacq <= tcal) return(0);	// underflow
	t = tacq - tcal;
	if(t >= tcal) return(0xff);	// overflow

	// *** calculate scaled result ***
	t = scaleSADC(tcal,t);
	return (unsigned char)t;
	}

//============================================================================