1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/voltmeter.c	Sun Jan 27 10:11:40 2013 +0200
     1.3 @@ -0,0 +1,252 @@
     1.4 +#define F_CLK	1000000
     1.5 +#define F_CPU	1000000
     1.6 +
     1.7 +#include <stdio.h>
     1.8 +#include <avr/io.h>
     1.9 +#include <util/delay.h>
    1.10 +
    1.11 +/* hardware setup
    1.12 + * - PORT D: data bits
    1.13 + * - PORT C
    1.14 + *     bit 0: RS
    1.15 + *     bit 1: R/W
    1.16 + *     bit 2: E
    1.17 + */
    1.18 +
    1.19 +#define BIT_RS	3
    1.20 +#define BIT_RW	4
    1.21 +#define BIT_E	5
    1.22 +
    1.23 +#define CMD_CLEAR		1
    1.24 +#define CMD_RET			(1 << 1)
    1.25 +#define CMD_ENTRY_MODE	(1 << 2)
    1.26 +#define CMD_ONOFF		(1 << 3)
    1.27 +#define CMD_SHIFT		(1 << 4)
    1.28 +#define CMD_FUNC		(1 << 5)
    1.29 +#define CMD_CGRAM_ADDR	(1 << 6)
    1.30 +#define CMD_DDRAM_ADDR	(1 << 7)
    1.31 +
    1.32 +#define FUNC_BUS_4BIT	0
    1.33 +#define FUNC_BUS_8BIT	(1 << 4)
    1.34 +#define FUNC_LINES_1	0
    1.35 +#define FUNC_LINES_2	(1 << 3)
    1.36 +#define FUNC_FONT_5x8	0
    1.37 +#define FUNC_FONT_5x11	(1 << 2)
    1.38 +
    1.39 +#define ONOFF_DISP			(1 << 2)
    1.40 +#define ONOFF_CURSOR		(1 << 1)
    1.41 +#define ONOFF_CURSOR_POS	1
    1.42 +
    1.43 +void setup_adc(void);
    1.44 +long read_adc(void);
    1.45 +
    1.46 +void lcd_init(void);
    1.47 +void lcd_clear(void);
    1.48 +void lcd_set_cursor_addr(unsigned int addr);
    1.49 +void lcd_putchar(char c);
    1.50 +void lcd_putstr(const char *str);
    1.51 +int lcd_stream_write(char c, FILE *fp);
    1.52 +void lcd_wait_busy(void);
    1.53 +static void enable(void);
    1.54 +static void set_bit(int bit);
    1.55 +static void clear_bit(int bit);
    1.56 +void delay(int x);
    1.57 +
    1.58 +#define NSDELAY()	asm volatile ("nop")
    1.59 +#define DEBUG(i)	(PORTB = (1 << (i)))
    1.60 +
    1.61 +FILE stream_lcd = FDEV_SETUP_STREAM(lcd_stream_write, NULL, _FDEV_SETUP_WRITE);
    1.62 +
    1.63 +int main(void)
    1.64 +{
    1.65 +	stdout = stderr = &stream_lcd;
    1.66 +
    1.67 +	DDRC = 0xfe;
    1.68 +	PORTC = 0;	/* disable pullups */
    1.69 +
    1.70 +	lcd_init();
    1.71 +	lcd_clear();
    1.72 +
    1.73 +	printf("initializing...");
    1.74 +	setup_adc();
    1.75 +
    1.76 +	for(;;) {
    1.77 +		long val = read_adc();
    1.78 +		double ref = 1.08 * 1.47 / 0.47;
    1.79 +		double voltage = ref * (double)val / (double)1024;
    1.80 +		lcd_clear();
    1.81 +
    1.82 +		if(val == 1023) {
    1.83 +			printf("*** RANGE ***   ");
    1.84 +		} else {
    1.85 +			printf("%.2f volts      ", voltage);
    1.86 +		}
    1.87 +		_delay_ms(500);
    1.88 +	}
    1.89 +	return 0;
    1.90 +}
    1.91 +
    1.92 +void setup_adc(void)
    1.93 +{
    1.94 +	/* disable digital input buffer on ADC0 pin */
    1.95 +	DIDR0 = 1;
    1.96 +
    1.97 +	/* use the internal bandgap as a reference */
    1.98 +	ADMUX = 3 << REFS0;
    1.99 +
   1.100 +	/* - enable ADC
   1.101 +	 * - set ADC clock prescaler to clock / 8
   1.102 +	 */
   1.103 +	ADCSRA = (1 << ADEN) | (3 << ADPS0);
   1.104 +}
   1.105 +
   1.106 +long read_adc(void)
   1.107 +{
   1.108 +	long low;
   1.109 +
   1.110 +	/* start conversion */
   1.111 +	ADCSRA |= (1 << ADSC);
   1.112 +
   1.113 +	/* wait while converting */
   1.114 +	while(ADCSRA & (1 << ADSC));
   1.115 +
   1.116 +	low = ADCL;
   1.117 +	return low | ((long)ADCH << 8);
   1.118 +}
   1.119 +
   1.120 +void lcd_init(void)
   1.121 +{
   1.122 +	DDRD = 0x0f;	/* port d[0, 3] -> output */
   1.123 +
   1.124 +	/* make sure the display has time to boot up */
   1.125 +	_delay_ms(20);
   1.126 +
   1.127 +	clear_bit(BIT_RW);
   1.128 +
   1.129 +	clear_bit(BIT_E);
   1.130 +	clear_bit(BIT_RS);
   1.131 +	PORTD = CMD_FUNC | FUNC_BUS_8BIT | FUNC_LINES_2 | FUNC_FONT_5x8;
   1.132 +	enable();
   1.133 +	lcd_wait_busy();
   1.134 +
   1.135 +	clear_bit(BIT_RS);
   1.136 +	PORTD = CMD_ONOFF | ONOFF_DISP | ONOFF_CURSOR;
   1.137 +	enable();
   1.138 +	lcd_wait_busy();
   1.139 +
   1.140 +	clear_bit(BIT_RS);
   1.141 +	PORTD = CMD_ENTRY_MODE | (1 << 1);
   1.142 +	enable();
   1.143 +	lcd_wait_busy();
   1.144 +}
   1.145 +
   1.146 +void lcd_clear(void)
   1.147 +{
   1.148 +	DDRD = 0xff;	/* port d -> output */
   1.149 +
   1.150 +	clear_bit(BIT_RW);
   1.151 +
   1.152 +	clear_bit(BIT_E);
   1.153 +	clear_bit(BIT_RS);
   1.154 +	PORTD = CMD_CLEAR;
   1.155 +	enable();
   1.156 +	lcd_wait_busy();
   1.157 +}
   1.158 +
   1.159 +void lcd_set_cursor_addr(unsigned int addr)
   1.160 +{
   1.161 +	DDRD = 0xff;	/* port d -> output */
   1.162 +
   1.163 +	clear_bit(BIT_RW);
   1.164 +
   1.165 +	clear_bit(BIT_E);
   1.166 +	clear_bit(BIT_RS);
   1.167 +	PORTD = CMD_DDRAM_ADDR | addr;
   1.168 +	enable();
   1.169 +	lcd_wait_busy();
   1.170 +}
   1.171 +
   1.172 +void lcd_putchar(char c)
   1.173 +{
   1.174 +	DDRD = 0xff;	/* port d -> output */
   1.175 +
   1.176 +	clear_bit(BIT_RW);
   1.177 +
   1.178 +	set_bit(BIT_RS);
   1.179 +	PORTD = c;
   1.180 +	enable();
   1.181 +	lcd_wait_busy();
   1.182 +}
   1.183 +
   1.184 +void lcd_putstr(const char *str)
   1.185 +{
   1.186 +	while(*str) {
   1.187 +		lcd_putchar(*str++);
   1.188 +	}
   1.189 +}
   1.190 +
   1.191 +int lcd_stream_write(char c, FILE *fp)
   1.192 +{
   1.193 +	/* TODO terminal shit handling */
   1.194 +	lcd_putchar(c);
   1.195 +	return 0;
   1.196 +}
   1.197 +
   1.198 +void lcd_wait_busy(void)
   1.199 +{
   1.200 +	unsigned char data;
   1.201 +
   1.202 +	DDRD = 0;		/* port d -> input */
   1.203 +	PORTD = 0;		/* disable pull-ups */
   1.204 +
   1.205 +	do {
   1.206 +		NSDELAY();
   1.207 +		clear_bit(BIT_E);
   1.208 +		clear_bit(BIT_RS);
   1.209 +		set_bit(BIT_RW);
   1.210 +		/*PIND = 0xff;*/
   1.211 +
   1.212 +		NSDELAY();
   1.213 +		set_bit(BIT_E);
   1.214 +		NSDELAY();
   1.215 +		data = PIND;
   1.216 +		clear_bit(BIT_E);
   1.217 +		clear_bit(BIT_RW);
   1.218 +
   1.219 +	} while(data & (1 << 7));
   1.220 +
   1.221 +	DDRD = 0xff;	/* port d -> output */
   1.222 +}
   1.223 +
   1.224 +static void enable(void)
   1.225 +{
   1.226 +	NSDELAY();
   1.227 +	set_bit(BIT_E);
   1.228 +	NSDELAY();
   1.229 +	clear_bit(BIT_E);
   1.230 +	NSDELAY();
   1.231 +}
   1.232 +
   1.233 +static void set_bit(int bit)
   1.234 +{
   1.235 +	PORTC |= 1 << bit;
   1.236 +}
   1.237 +
   1.238 +static void clear_bit(int bit)
   1.239 +{
   1.240 +	PORTC &= ~(1 << bit);
   1.241 +}
   1.242 +
   1.243 +
   1.244 +void delay(int x)
   1.245 +{
   1.246 +	int i, j;
   1.247 +
   1.248 +	while(x-- > 0) {
   1.249 +		for(i=0; i<90; i++) {
   1.250 +			for(j=0; j<6; j++) {
   1.251 +				asm volatile("nop");
   1.252 +			}
   1.253 +		}
   1.254 +	}
   1.255 +}