mouldy.org

#include < avr/io.h>
#include < avr/interrupt.h>
#include < util/twi.h>

typedef unsigned char uchar;

void delay_ms(unsigned char ms)
/* badly mangled delay_ms */
{
	unsigned short outer1, outer2;
     	outer1 = 1; 

    	while (outer1) {
		outer2 = 1000;
		while (outer2) {
			while ( ms ) ms--;
			outer2--;
		}
		outer1--;
	}
}

void wait_a_bit(void)
{
	int i;
	
	for (i = 0; i < 150; i++)
		delay_ms(0);
}

void led_mid(void)
{
	OCR1A = 80;
}

void led_off(void)
{
	OCR1A = 0;
}

void led_on(void)
{
	OCR1A = 255;
}

void twi_init(void)
{
	// set TWI clock rate
	TWSR |= 3; // div by 64
	TWBR = 4; // div by another 3
	// final clock rate should be about 10kHz

/*set initial state of TWCR
FIXME stub*/
}

void debug(uchar val)
{
	PORTA = val;
}

uchar twi_write_byte(uchar addr, uchar data)
{
	// I-bit in SREG must be set

	// write to TWCR to start transmission: TWINT 1, TWSTA 1, TWSTO 0, TWEN 1
	TWCR = (1 << TWINT | 1 << TWSTA | 1 << TWEN);

	while (!(TWCR & (1 << TWINT)))
			;

	if (((TWSR & 0xf8) != TW_START) && ((TWSR & 0xf8) != TW_REP_START)) // added by Ian; repeated START is OK
		return 1; // error

	TWDR = (addr << 1) | TW_WRITE;
	TWCR = (1 << TWINT) | (1 << TWEN);

	while (!(TWCR & (1 << TWINT)))
		;

	if ((TWSR & 0xf8) != TW_MT_SLA_ACK)
		return 2; // error

	TWDR = data;
	TWCR = (1 << TWINT) | (1 << TWEN);

	while (!(TWCR & (1 << TWINT)))
		;

	if ((TWSR & 0xf8) != TW_MT_DATA_ACK)
		return 3; // error

	TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
	while (!(TWCR & (1 << TWSTO))) // Ian's addition: make sure STOP condition has finished
		;

	return 0;
}

void debug_init(void)
{
	DDRA = 0xff;
}

void wait_fast(void)
{
	int i;
	
	for (i = 0; i < 30; i++)
		delay_ms(0);
}

int main(void)
{
	int err = 0;

	/* enable  PD5 as output */
	DDRD |= 1 << PD5;

	/* set up the PWM */
	TCCR1A |= 1 << COM1A1; // clear OC1A/OC1B on compare match during upcount; set on match during downcount
	TCCR1A |= 1 << WGM10; // PWM, phase correct, 8-bit
	TCCR1B |= 1 << CS10; // internal clock, 1:1 prescale

	/* we want to set the LED to mid brightness during init, then set it to full-on if i2c transmit is successful, full-off otherwise */

	debug_init();
	
	led_on();
	debug(0xff);
	wait_a_bit();
	led_mid();
	debug(0x0);
	wait_a_bit();
	
	twi_init();
/*
; The truth table for the output is:
; Reverse Brake | A B C D
; --------------+--------
; 0       0     | P 0 0 P
; 0       1     | 0 0 P P
; 1       0     | 0 P P 0
; 1       1     | 0 0 P P

twi_command:
	; command format: 8 bits
	; ccdbssss
	; cc = channel number. Only the LSB is used on this device.
	; d = direction. 0 forward, 1 backwards
	; b = brake. 0 no brake, 1 brake
	; ssss = speed. higher values -> higher speed
*/

	int speed = 0;
	int count = 0;
	int dir = 0;

	while (1) {
		dir = ~dir;

		//if (dir)
		//	speed++;

		speed = 0xf;

		int addr = 0b1000000;
		int data_base = 0b00000000;
		int data = data_base | (speed & 0xf) | (dir & 0b00100000);
		debug(1);
		err = twi_write_byte(addr, data);
		
		debug(data);

		/* want to send the command '01001010' to address '1100000' as a write */
		//err = twi_write_byte(0b1000000, 0b01111010); // 2/3 brake port 1
		//wait_a_bit();
		//err = twi_write_byte(0b1000000, 0b00001000); // 1/2 fwd port 0

		//err = twi_write_byte(0b1000000, 0b01111010); // 2/3 brake port 1
		//err = twi_write_byte(0b1000000, 0b00101010); // 2/3 back port 0
		//err = twi_write_byte(0b1000000, 0b01101010); // 2/3 back port 1
		//err = twi_write_byte(0b1000000, 0b01001010); // 2/3 forward port 1

		if (err) {
			while (1) {
				led_off();
				debug(err);
				wait_a_bit();
				led_on();
				debug(TWSR);
				wait_a_bit();
			}
		} else {
			led_on();
		}

		//debug(speed);
		wait_a_bit();
		wait_a_bit();

	}

	return 0; // we should never hit this
}