1.1 --- a/voltmeter.c	Sun Jan 27 10:11:40 2013 +0200
     1.2 +++ b/voltmeter.c	Mon Jan 28 09:52:15 2013 +0200
     1.3 @@ -3,6 +3,7 @@
     1.4  
     1.5  #include <stdio.h>
     1.6  #include <avr/io.h>
     1.7 +#include <avr/interrupt.h>
     1.8  #include <util/delay.h>
     1.9  
    1.10  /* hardware setup
    1.11 @@ -12,6 +13,7 @@
    1.12   *     bit 1: R/W
    1.13   *     bit 2: E
    1.14   */
    1.15 +#define LCD_BUS_WIDTH	8
    1.16  
    1.17  #define BIT_RS	3
    1.18  #define BIT_RW	4
    1.19 @@ -57,10 +59,23 @@
    1.20  
    1.21  FILE stream_lcd = FDEV_SETUP_STREAM(lcd_stream_write, NULL, _FDEV_SETUP_WRITE);
    1.22  
    1.23 +int bn_pressed;
    1.24 +unsigned char foo;
    1.25 +
    1.26  int main(void)
    1.27  {
    1.28  	stdout = stderr = &stream_lcd;
    1.29  
    1.30 +	/* port B[0] out -> backlight
    1.31 +	 * port B[1] in <- backlight switch
    1.32 +	 */
    1.33 +	DDRB = 1;
    1.34 +	PORTB = 0xfe;	/* enable all pullups, leave bit0 -> 0 (backlight) */
    1.35 +	/* enable PIN B1 interrupt */
    1.36 +	PCMSK0 = 2;
    1.37 +	PCICR = 1;
    1.38 +	sei();	/* enable interrupts */
    1.39 +
    1.40  	DDRC = 0xfe;
    1.41  	PORTC = 0;	/* disable pullups */
    1.42  
    1.43 @@ -74,18 +89,36 @@
    1.44  		long val = read_adc();
    1.45  		double ref = 1.08 * 1.47 / 0.47;
    1.46  		double voltage = ref * (double)val / (double)1024;
    1.47 +
    1.48  		lcd_clear();
    1.49  
    1.50  		if(val == 1023) {
    1.51 -			printf("*** RANGE ***   ");
    1.52 +			printf("*** RANGE ***");
    1.53  		} else {
    1.54 -			printf("%.2f volts      ", voltage);
    1.55 +			printf("%.2f volts", voltage);
    1.56 +		}
    1.57 +
    1.58 +		/* check if the backlight button was pressed */
    1.59 +		if(bn_pressed & 1) {
    1.60 +			if(PORTB & 1) {
    1.61 +				PORTB &= 0xfe;
    1.62 +			} else {
    1.63 +				PORTB |= 1;
    1.64 +			}
    1.65 +			bn_pressed = 0;
    1.66  		}
    1.67  		_delay_ms(500);
    1.68  	}
    1.69  	return 0;
    1.70  }
    1.71  
    1.72 +
    1.73 +ISR(PCINT0_vect) {
    1.74 +	if((PINB & 2) == 0) {
    1.75 +		bn_pressed = 1;
    1.76 +	}
    1.77 +}
    1.78 +
    1.79  void setup_adc(void)
    1.80  {
    1.81  	/* disable digital input buffer on ADC0 pin */
    1.82 @@ -114,10 +147,39 @@
    1.83  	return low | ((long)ADCH << 8);
    1.84  }
    1.85  
    1.86 +void lcd_write_byte(unsigned char byte)
    1.87 +{
    1.88 +#if LCD_BUS_WIDTH == 8
    1.89 +	DDRD = 0xff;
    1.90 +	PORTD = byte;
    1.91 +#else
    1.92 +	DDRD = (DDRD & 0xf0) | 0xf;
    1.93 +
    1.94 +	PORTD = (PORTD & 0xf0) | ((byte >> 4) & 0xf);
    1.95 +	PORTD = (PORTD & 0xf0) | (byte & 0xf);
    1.96 +#endif
    1.97 +}
    1.98 +
    1.99 +unsigned char lcd_read_byte(void)
   1.100 +{
   1.101 +#if LCD_BUS_WIDTH == 8
   1.102 +	DDRD = 0;
   1.103 +	PORTD = 0;	/* disable pull-ups */
   1.104 +
   1.105 +	return PIND;
   1.106 +#else
   1.107 +	unsigned char byte;
   1.108 +
   1.109 +	DDRD = DDRD & 0xf0;
   1.110 +	PORTD &= 0xf0;	/* disable pull-ups */
   1.111 +
   1.112 +	byte = (PIND & 0xf) << 4;
   1.113 +	return byte | (PIND & 0xf);
   1.114 +#endif
   1.115 +}
   1.116 +
   1.117  void lcd_init(void)
   1.118  {
   1.119 -	DDRD = 0x0f;	/* port d[0, 3] -> output */
   1.120 -
   1.121  	/* make sure the display has time to boot up */
   1.122  	_delay_ms(20);
   1.123  
   1.124 @@ -125,55 +187,53 @@
   1.125  
   1.126  	clear_bit(BIT_E);
   1.127  	clear_bit(BIT_RS);
   1.128 -	PORTD = CMD_FUNC | FUNC_BUS_8BIT | FUNC_LINES_2 | FUNC_FONT_5x8;
   1.129 +#if LCD_BUS_WIDTH == 8
   1.130 +	lcd_write_byte(CMD_FUNC | FUNC_BUS_8BIT | FUNC_LINES_2 | FUNC_FONT_5x8);
   1.131 +#else
   1.132 +	lcd_write_byte(CMD_FUNC | FUNC_BUS_4BIT | FUNC_LINES_2 | FUNC_FONT_5x8);
   1.133 +#endif
   1.134  	enable();
   1.135  	lcd_wait_busy();
   1.136  
   1.137  	clear_bit(BIT_RS);
   1.138 -	PORTD = CMD_ONOFF | ONOFF_DISP | ONOFF_CURSOR;
   1.139 +	lcd_write_byte(CMD_ONOFF | ONOFF_DISP);
   1.140  	enable();
   1.141  	lcd_wait_busy();
   1.142  
   1.143  	clear_bit(BIT_RS);
   1.144 -	PORTD = CMD_ENTRY_MODE | (1 << 1);
   1.145 +	lcd_write_byte(CMD_ENTRY_MODE | (1 << 1));
   1.146  	enable();
   1.147  	lcd_wait_busy();
   1.148  }
   1.149  
   1.150  void lcd_clear(void)
   1.151  {
   1.152 -	DDRD = 0xff;	/* port d -> output */
   1.153 -
   1.154  	clear_bit(BIT_RW);
   1.155  
   1.156  	clear_bit(BIT_E);
   1.157  	clear_bit(BIT_RS);
   1.158 -	PORTD = CMD_CLEAR;
   1.159 +	lcd_write_byte(CMD_CLEAR);
   1.160  	enable();
   1.161  	lcd_wait_busy();
   1.162  }
   1.163  
   1.164  void lcd_set_cursor_addr(unsigned int addr)
   1.165  {
   1.166 -	DDRD = 0xff;	/* port d -> output */
   1.167 -
   1.168  	clear_bit(BIT_RW);
   1.169  
   1.170  	clear_bit(BIT_E);
   1.171  	clear_bit(BIT_RS);
   1.172 -	PORTD = CMD_DDRAM_ADDR | addr;
   1.173 +	lcd_write_byte(CMD_DDRAM_ADDR | addr);
   1.174  	enable();
   1.175  	lcd_wait_busy();
   1.176  }
   1.177  
   1.178  void lcd_putchar(char c)
   1.179  {
   1.180 -	DDRD = 0xff;	/* port d -> output */
   1.181 -
   1.182  	clear_bit(BIT_RW);
   1.183  
   1.184  	set_bit(BIT_RS);
   1.185 -	PORTD = c;
   1.186 +	lcd_write_byte(c);
   1.187  	enable();
   1.188  	lcd_wait_busy();
   1.189  }
   1.190 @@ -196,9 +256,6 @@
   1.191  {
   1.192  	unsigned char data;
   1.193  
   1.194 -	DDRD = 0;		/* port d -> input */
   1.195 -	PORTD = 0;		/* disable pull-ups */
   1.196 -
   1.197  	do {
   1.198  		NSDELAY();
   1.199  		clear_bit(BIT_E);
   1.200 @@ -209,13 +266,11 @@
   1.201  		NSDELAY();
   1.202  		set_bit(BIT_E);
   1.203  		NSDELAY();
   1.204 -		data = PIND;
   1.205 +		data = lcd_read_byte();
   1.206  		clear_bit(BIT_E);
   1.207  		clear_bit(BIT_RW);
   1.208  
   1.209  	} while(data & (1 << 7));
   1.210 -
   1.211 -	DDRD = 0xff;	/* port d -> output */
   1.212  }
   1.213  
   1.214  static void enable(void)