Lメータ(インダクタンスの測定器)

/*
 *  l_meter.c
 *  フランクリン発振回路の発振周波数とC = 1000PFよりLの値を得て、
 *  LCDに発振周波数とLの値を表示する。
 *  ATmega328P
 *
 *
 *  Fuses(システムクロック:20MHz)
 *
 *              水晶
 *  EXTENDED    0xFD
 *  HIGH        0xD9
 *  LOW         0xF7
 */

#include <stdio.h>
#include <string.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#define F_CPU 20.0E6                /* 20 MHz */
#include <util/delay.h>

#define LCD_RS_H PORTC |= _BV(5)
#define LCD_E_H PORTC |= _BV(4)
#define LCD_RS_L PORTC &= ~_BV(5)
#define LCD_E_L PORTC &= ~_BV(4)
#define LCD_DB PORTC
typedef union tagCOUNT{
    unsigned long DWORD;
    struct{
        unsigned short lcount;
        unsigned short ucount;
    } WORD;
} COUNT;
#define PI 3.1415926535897932384626433832795
#define round(x) ((x)>=0?(long)((x)+0.5):(long)((x)-0.5))

void delay_us(unsigned short t){while(t--) _delay_us(1);}
void delay_ms(unsigned short t){while(t--) _delay_ms(1);}
void initLCD(void);
void initTIMER(void);
void clear_lcd(void);
void print_lcd(int x, int y, char *s);

unsigned long ltime;
unsigned short ucount;
COUNT freq;

int main(void)
{
    char buffer[32];
    int i;
    double freq2, lx;

    /* ATmega328P */
    DDRB = 0b00000000;      /* XTAL2 XTAL1 SCK   MISO  MOSI  ----- ----- ----- */
    DDRC = 0b00111111;      /* xxxxx RESET RS    E     DB7   DB6   DB5   DB4   */
    DDRD = 0b00000000;      /* ----- ----- T1    ----- ----- ----- ----- ----- */
    PORTB = 0b00111111;
    PORTC = 0b00000000;
    PORTD = 0b11011111;

    initLCD();
    initTIMER();
    sei();

    clear_lcd();
    print_lcd(5, 0, "START");
    delay_ms(2000);

    while(1){
        freq2 = freq.DWORD / 1.024;
        // f = 1 / (2 * Π * √L * √C)
        // f * f = 1 / (4 * Π * Π * L * C)
        // L = 1 / (f * f * 4 * Π * Π * C)
        lx = 1.0E6 / (freq2 * freq2 * 4.0 * PI * PI * 1000.0E-12);

        sprintf(buffer, "%11lu", (unsigned long)round(freq2));
        if(buffer[4] != ' '){
            for(i=0; i<3; i++)
                buffer[i] = buffer[2 + i];
            buffer[3] = ',';
            for(i=0; i<3; i++)
                buffer[4 + i] = buffer[5 + i];
            buffer[7] = ',';
        }
        else if(buffer[7] != ' '){
            for(i=0; i<3; i++)
                buffer[4 + i] = buffer[5 + i];
            buffer[7] = ',';
        }
        strcat(buffer, "Hz");
        clear_lcd();
        print_lcd(1, 0, buffer);

        sprintf(buffer, "%11lu", (unsigned long)round(lx));
        if(buffer[4] != ' '){
            for(i=0; i<3; i++)
                buffer[i] = buffer[2 + i];
            buffer[3] = ',';
            for(i=0; i<3; i++)
                buffer[4 + i] = buffer[5 + i];
            buffer[7] = ',';
        }
        else if(buffer[7] != ' '){
            for(i=0; i<3; i++)
                buffer[4 + i] = buffer[5 + i];
            buffer[7] = ',';
        }
        strcat(buffer, "uH");
        print_lcd(1, 1, buffer);

        delay_ms(1000);
    }
}

void initTIMER(void)
{
    TCCR0A = 0b00000010;    /* CTC動作 */
    TCCR0B = 0b00000101;    /* clk / 1024 */
    OCR0A = 20 - 1;         /* (1024 / 20MHz) * 20 = 1.024mS */
    TIMSK0 = 0b00000010;    /* 比較A割り込み要求有効 */

    TCCR1B = 0b00000111;    /* 外部クロックT1 (PD5)ピンの立ち上がりエッジ */
    TIMSK1 = 0b00000001;    /* オーバーフロー割り込み許可 */
}

/*
 *  TIMER0の割り込み(1.024mS)
 */
ISR(TIMER0_COMPA_vect)
{
    static unsigned long ot;

    ++ltime;

    if((unsigned long)(ltime - ot) >= 1000){
        ot = ltime;
        TCCR1B = 0b00000000;    /* カウント停止 */
        freq.WORD.lcount = TCNT1;
        TCNT1 = 0;
        TCCR1B = 0b00000111;    /* 外部クロックT1 (PD5) ピンの立ち上がりエッジ */
        freq.WORD.ucount = ucount;
        ucount = 0;
    }
}

ISR(TIMER1_OVF_vect)
{
    ++ucount;
}

/* DB:4BIT(LOWER) */
void lcd_c4(unsigned char data)
{
    unsigned char tmp;

    LCD_RS_L;                       /* RS --> L */
    LCD_E_H;                        /* E --> H */
    tmp = (unsigned char)(LCD_DB & 0xf0);
    tmp |= (unsigned char)(data & 0x0f);
    LCD_DB = tmp;
    LCD_E_L;                        /* E --> L */
    delay_us(40);
}

void lcd_c(unsigned char data)
{
    unsigned char tmp;

    LCD_RS_L;                       /* RS --> L */
    LCD_E_H;                        /* E --> H */
    tmp = (unsigned char)(LCD_DB & 0xf0);
    tmp |= (unsigned char)(data  >> 4 & 0x0f);
    LCD_DB = tmp;
    LCD_E_L;                        /* E --> L */
    delay_us(1);
    LCD_E_H;                        /* E --> H */
    tmp = (unsigned char)(LCD_DB & 0xf0);
    tmp |= (unsigned char)(data & 0x0f);
    LCD_DB = tmp;
    LCD_E_L;                        /* E --> L */
    delay_us(40);
}

/* DB:4BIT(LOWER) */
void lcd_d(unsigned char data)
{
    unsigned char tmp;

    LCD_RS_H;                       /* RS --> H */
    LCD_E_H;                        /* E --> H */
    tmp = (unsigned char)(LCD_DB & 0xf0);
    tmp |= (unsigned char)(data  >> 4 & 0x0f);
    LCD_DB = tmp;
    LCD_E_L;                        /* E --> L */
    delay_us(1);
    LCD_E_H;                        /* E --> H */
    tmp = (unsigned char)(LCD_DB & 0xf0);
    tmp |= (unsigned char)(data & 0x0f);
    LCD_DB = tmp;
    LCD_E_L;                        /* E --> L */
    delay_us(40);
}

void initLCD(void)
{
    delay_ms(15);
    lcd_c4(0x03);
    delay_ms(5);
    lcd_c4(0x03);
    delay_us(100);
    lcd_c4(0x03);
    lcd_c4(0x02);
    lcd_c(0x28);                    /* Function Set */
    lcd_c(0x08);                    /* Display OFF */
    lcd_c(0x01);                    /* Clear Display */
    delay_ms(2);
    lcd_c(0x06);                    /* Enter Mode */
    lcd_c(0x0c);                    /* Display ON */
}

void clear_lcd(void)
{
    lcd_c(0x01);                    /* Clear Display (& Cursor At Home) */
    delay_ms(2);
/// lcd_c(0x02);                    /* Cursor At Home */
/// delay_ms(2);
}

void cursor_lcd(int x, int y)
{
    lcd_c((unsigned char)(0x80 + y * 0x40 + x));
}

void print_lcd(int x, int y, char *s)
{
    cursor_lcd(x, y);

    while(*s)
        lcd_d((unsigned char)*s++);
}