//
//
// hello.H-bridge.44.DC.c
//
// H-bridge DC motor hello-world
//
// Neil Gershenfeld
// 11/18/12
//
// (c) Massachusetts Institute of Technology 2012
// This work may be reproduced, modified, distributed,
// performed, and displayed for any purpose. Copyright is
// retained and must be preserved. The work is provided
// as is; no warranty is provided, and users accept all 
// liability.
//

#include <avr/io.h>
#include <util/delay.h>

#define output(directions,pin) (directions |= pin) // set port direction for output
#define input(directions,pin) (directions &= (~pin)) // set port direction for input
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin
#define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
#define bit_delay_time 102 // bit delay for 9600 with overhead
#define bit_delay() _delay_us(bit_delay_time) // RS232 bit delay
#define half_bit_delay() _delay_us(bit_delay_time/2) // RS232 half bit delay
#define char_delay() _delay_ms(10) // char delay
#define on_delay() _delay_us(3) // PWM on time
#define fast_off_delay() _delay_us(1) // PWM fast off time
#define medium_off_delay() _delay_us(3) // PWM medium off time
#define slow_off_delay() _delay_us(5) // PWM slow off time
#define PWM_count 20000 // number of PWM cycles
#define cycle_count 8 // number of speed cycles

#define bridge_port PORTA // H-bridge port
#define bridge_direction DDRA // H-bridge direction
#define IN1 (1 << PA3) // IN1
#define IN2 (1 << PA2) // IN2

#define serial_port PORTA
#define serial_direction DDRA
#define serial_pins PINA
#define serial_pin_in (1 << PA6)
#define serial_pin_out (1 << PA7)



void get_char(volatile unsigned char *pins, unsigned char pin, char *rxbyte) {
	//
	// read character into rxbyte on pins pin
	//    assumes line driver (inverts bits)
	//
	*rxbyte = 0;
	while (pin_test(*pins,pin))
		//
		// wait for start bit
		//
		;
	//
	// delay to middle of first data bit
	//
	half_bit_delay();
	bit_delay();
	//
	// unrolled loop to read data bits
	//
	if pin_test(*pins,pin)
		*rxbyte |= (1 << 0);
	else
		*rxbyte |= (0 << 0);
	bit_delay();
	if pin_test(*pins,pin)
		*rxbyte |= (1 << 1);
	else
		*rxbyte |= (0 << 1);
	bit_delay();
	if pin_test(*pins,pin)
		*rxbyte |= (1 << 2);
	else
		*rxbyte |= (0 << 2);
	bit_delay();
	if pin_test(*pins,pin)
		*rxbyte |= (1 << 3);
	else
		*rxbyte |= (0 << 3);
	bit_delay();
	if pin_test(*pins,pin)
		*rxbyte |= (1 << 4);
	else
		*rxbyte |= (0 << 4);
	bit_delay();
	if pin_test(*pins,pin)
		*rxbyte |= (1 << 5);
	else
		*rxbyte |= (0 << 5);
	bit_delay();
	if pin_test(*pins,pin)
		*rxbyte |= (1 << 6);
	else
		*rxbyte |= (0 << 6);
	bit_delay();
	if pin_test(*pins,pin)
		*rxbyte |= (1 << 7);
	else
		*rxbyte |= (0 << 7);
	//
	// wait for stop bit
	//
	bit_delay();
	half_bit_delay();
	}


int main(void) {
	//
	// main
	//
	static uint16_t count;
	static uint8_t cycle;
	static char chr;
	//
	// set clock divider to /1
	//
	CLKPR = (1 << CLKPCE);
	CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
	//
	// initialize H-bridge pins
	//
	clear(bridge_port, IN1);
	output(bridge_direction, IN1);
	clear(bridge_port, IN2);
	output(bridge_direction, IN2);
		// initialize serial input pins
	set(serial_port, serial_pin_out);
	input(serial_direction, serial_pin_out);
	//
	// main loop
	//
	while (1) {
		get_char(&serial_pins, serial_pin_in, &chr);
		if (chr == '1')
			{
				//
				// turn forward slow
				//
				 for (cycle = 0; cycle < cycle_count; ++cycle) {
				clear(bridge_port, IN1);
				set(bridge_port, IN2);
				for (count = 0; count < PWM_count; ++count) {
					set(bridge_port, IN2);
					on_delay();
					clear(bridge_port, IN2);
					slow_off_delay();
				}
				}
			}
		
		if (chr == '2')
			{
				//
				// turn forward medium
				//
				for (cycle = 0; cycle < cycle_count; ++cycle) {
				clear(bridge_port, IN1);
				set(bridge_port, IN2);
				for (count = 0; count < PWM_count; ++count) {
					set(bridge_port, IN2);
					on_delay();
					clear(bridge_port, IN2);
					medium_off_delay();
				}
				}
			}

		if (chr == '3')
				{
			//
			// turn forward fast
			//
			for (cycle = 0; cycle < cycle_count; ++cycle) {
			clear(bridge_port, IN1);
			set(bridge_port, IN2);
			for (count = 0; count < PWM_count; ++count) {
				set(bridge_port, IN2);
				on_delay();
				clear(bridge_port, IN2);
				fast_off_delay();
				}
				}
				}
		}
	}