absolute_pos_encoder.c

8051 Absolute Encoder Positioner How to connect and drive absolute position encoder with SSI serial

/*===============================================
 (C) Easy Soft 07/2001
  C code for Programable Signal Controller
 - - - - - - - - - - - - - - - - - - - - - - - -
 Raisonance RC-51, version 6.4.16

 oscillator freq.22.1184 MHz
 controller AT89S8252
 ================================================ */

/* This is part of big program. You can use it like an example of absolute position encoder reading.
	I have been using Siemens' encoder 6FX2001-5FS12 with RS485 interface */

#pragma SMALL
#include <reg52.h>

/* characters pattern defintions table */
char code CGRom1[65] = {0xAA,0x55,0xAA,0x55,0xAA,0x55,0xAA,0x55,		// "hash"		0x00
							  	0xFF,0xFF,0xF9,0xF3,0xE7,0xF3,0xF9,0xFF,		// left			0x01
							  	0xFF,0xFF,0xF3,0xF9,0xFC,0xF9,0xF3,0xFF,		// right			0x02
				           	0xFF,0xFF,0xFB,0xF1,0xE4,0xEE,0xFF,0xFF,		// up				0x03
				           	0xFF,0xFF,0xFF,0xEE,0xE4,0xF1,0xFB,0xFF,		// down			0x04
								0xC0,0xC0,0xFF,0xF1,0xF1,0xF1,0xFF,0xC0,		// empty box	0x05
							  	0xC0,0xC0,0xFF,0xFF,0xFF,0xFF,0xFF,0xC0,		// filled box	0x06
							  	0xE0,0xFF,0xFF,0xFF,0xE0,0xE0,0xE0,0xE0,		// line			0x07
				           	0x00};

/* position to degree factor */
#define FACTOR 11.38

/* LCD display is working like external memory,0x00 is its base address */
at 0x00 pdata char LcdCtrlRegister, LcdVideoRam, LcdReadCtrl, LcdRead;

unsigned int POS;				// absolute encoder position 12-bit Gray encoded
int ZERO = 0;					// calibration of encoder



/************************** EXTERNAL ROUTINES IN ASSEMBLER LANGUAGE ******************************/
/* encoder position reading; clock signal must be within range from 100kHz up to 1MHz */
extern unsigned int PositionRead(void);


/************************************* "C" ROUTINES **********************************************/

/* 12 bit Gray to Binary conversion */
unsigned int Gray2Bin(unsigned int N)
{
	char i;
	unsigned int A = N;
	
	for (i = 1; i != 13; i++) N = N^(A >> i);
	
	return (N);
}


/* changing absolute position in binary to degree */
unsigned int DPE(void)
{
	int N;
	
	N = Gray2Bin(PositionRead());
	N = N / FACTOR;
	N = N - ZERO;
   if (N < 0) N = N + 360;
	return(N);
}


/* delay about 1 ms for 22.1184MHz crystal */
void delay (unsigned int k) 
{
	unsigned int i,j;
	for ( j = 0; j < k; j++)
		for (i = 0; i <= 148;) {
			i++;
		}
}


/* wait if LCD is busy */
void LcdWait (void) 
{
	while (LcdReadCtrl & 0x80);
}


/* write a byte to LCD's controll register */
void WriteToLcdCtrlRegister(char X) 
{
	LcdCtrlRegister = X;
	LcdWait();
}


/* direct byte writing to LCD */
void LcdWrite(char X) 
{
	LcdVideoRam = X;
	LcdWait();
}


/* clear LCD screen */
void LcdClrScr(void) 
{
	LcdCtrlRegister = 0x01;
	LcdWait();
}


/* LCD initializing */
void LcdInitialize(void) 
{
	delay(15);
	LcdCtrlRegister = 0x30;
	delay(10);
	LcdCtrlRegister = 0x30;
	delay(10);
	WriteToLcdCtrlRegister(0x30);
	WriteToLcdCtrlRegister(0x3C);
	WriteToLcdCtrlRegister(0x08);
	WriteToLcdCtrlRegister(0x01);
	WriteToLcdCtrlRegister(0x06);
	WriteToLcdCtrlRegister(0x0C);
}

	
/* set cursor position at X, Y coordinates */
void GotoXY(char x, char y) 
{
	char addr;
	
	switch (y) {
		case 0:
			addr = 0x80+x;
			break;
		case 1:
			addr = 0xC0+x;
			break;
		case 2:
			addr = 0x94+x;
			break;
		case 3:
			addr = 0xD4+x;
			break;
	}
	LcdCtrlRegister = addr;
	LcdWait();
}


/* routine displays text at X, Y coordinates */
void WriteTextXY(char x, char y, char code *S) 
{
	while (*S) {
		GotoXY(x, y);
		LcdWrite(*S);
		x++; 
		S++;
		if (x > 19) {
			x = 0; 
			y++;
		}
	}
}


/* routine defines yourown characters */
void DefineSpecialCharacters(char *ptr) 
{
	LcdCtrlRegister = 0x40;		// set cgram definition mode
	LcdWait();
	while (*ptr != 0x00) {
		LcdWrite(*ptr);
		ptr++;
	}
	LcdCtrlRegister = 0x80;		// switch to normal mode
	LcdWait();
}


/* Bin to Dec conversion & writing the number in X, Y coordinates */
void DisplayDegree(char x, char y, int N) 
{
	int l=0, D;
	
	if (N > 359) {
		WriteTextXY(x, y, "---");
	} else {
		GotoXY(x, y);
		if (N < 0) {
			LcdWrite(0x2D);
			N = -N;
		}
		D = N;
		if (N >= 100) {
			l = D/100;
			LcdWrite(l+0x30);
			D = D - 100*l;
		}
		if (N >= 10) {
			l = D/10;
			LcdWrite(l+0x30);					// 10
			D = D - 10*l;
		}
		l = D;
		LcdWrite(l+0x30);						// 1
		LcdWrite(0xDF);						// degree character
		LcdWrite(0x20);						// 2 blank spaces
		LcdWrite(0x20);
	}
}


// main programm
void main(void)
{
	LcdInitialize();					// inicjowanie wy渨ietlacza lcd (tryb 8-bit體)
	DefineSpecialCharacters(CGRom1);
	while (1) {
		POS = DPE();
		DisplayDegree(0, 0, POS);
	}
}