/*
	CPU: ATTiny85 @ 16 MHz(PLL) - Bootloader
	Fuses:
		- Low : F1
		- High: D7
		- Ext : FE
	B.O.D: Disabled
	Timer1 Clk: 64 MHz
*/
#define F_CPU 16000000UL	//16MHz PLL Clock Speed

//Includes
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdbool.h>
#include <stdio.h>

//GPIO Pins
#define SHUTDOWN 	PB0
#define PWM_OUT 	PB1
#define FEEDBACK_IN PB3
#define POTI_IN 	PB4

//ADC ADMUX Registers
#define POTI_ADC 	 00000010
#define FEEDBACK_ADC 00000011

//USI-UART
#define TX_PORT		PORTB
#define TX_PIN		PB2
#define TX_DDR		DDRB
#define TX_DDR_PIN	DDB2

//Global Variables
static uint8_t pwmVal;
volatile uint16_t tx_shift_reg = 0;
bool disabled = false;
char buffer[100];

//Functions
void initADC(void);
uint16_t readADC(uint8_t channel);
void UART_init();
void UART_tx(char character);
void UART_tx_str(char* string);

int main(void){
	
	//Setup IO Pins
	DDRB |= (1<<PWM_OUT);										//PWM as Output
	DDRB &= ~((1<<POTI_IN) | (1<<FEEDBACK_IN) | (1<<SHUTDOWN));	//Feedback, Shutdown and Poti Pin as Inputs
	
	initADC();													//Init Internal ADC
	
//	UART_init();												//Init Software Uart
	
	OCR1C = 212;												//Set PWM Frequency to 150KHz
	
	TCCR1 |= (1<<PWM1A) | (1<<COM1A1);							//Setup Timer 1 for PWM A
	
	PLLCSR = (1<<PLLE);											//Enable PLL
	PLLCSR |= (1<<PCKE);										//Enable PCK for Timer 1 64 MHz
	
	TCCR1 |= (1<<CS11);											//Prescaler PCK/2
	
	sei();														//Enable Interrupts
	
	OCR1A = 0;													//Set PWM to 0
	pwmVal = 0;													//Set Counter to 0
	
    while (1){
		if(PINB & (1<<SHUTDOWN)) {								//Check if Boost Converter is shutdown by main MCU(ATMega2560)
			disabled = true;									//Disable Boost Converter
			OCR1A = 0;											//Set PWM to 0
			pwmVal = 0;											//Set Counter to 0
		}else{
			disabled = false;									//Enable Boost Converter
		}	

		uint8_t potiInput = readADC(2) / 4;						//Read Poti ADC
		uint8_t feedbackInput = readADC(3) / 4;					//Read Feedback ADC
		if(potiInput > feedbackInput) {							//Check if Poti Voltage is bigger then Feedback Voltage
			if(pwmVal != 180) {									//Check if not reached max. PWM Value
				pwmVal = pwmVal + 1;							//Increase PWM by 1
				OCR1A = pwmVal;									//Set new PWM
			//	sprintf(buffer, "Increase PWM: %d\r\n", pwmVal);
			//	UART_tx_str(buffer);
			}
		}else if(potiInput < feedbackInput) {					//Check if Poti Voltage is smaller then Feedback Voltage
			if(pwmVal != 0) {									//Check if not reached min. PWM Value
				pwmVal = pwmVal - 1;							//Decrease PWM by 1
				OCR1A = pwmVal;									//Set new PWM
			//	sprintf(buffer, "Decrease PWM: %d\r\n", pwmVal);
			//	UART_tx_str(buffer);
			}
		}
    }
}

//Transmit Single Character
void UART_tx(char character){
   uint16_t local_tx_shift_reg = tx_shift_reg;
   //if sending the previous character is not yet finished, return
   //transmission is finished when tx_shift_reg == 0
   if(local_tx_shift_reg){return;}
   local_tx_shift_reg = (character<<1) | (1<<9);
   tx_shift_reg = local_tx_shift_reg;
   TCCR0B = (1<<CS01);
}

//Transmit String to UART
void UART_tx_str(char* string){
    while( *string ){
        UART_tx( *string++ );
        //wait until transmission is finished
        while(tx_shift_reg);
    }
}

//Init UART
void UART_init(){
   //set TX pin as output
   TX_DDR |= (1<<TX_DDR_PIN);
   TX_PORT |= (1<<TX_PIN);
   //set timer0 to CTC mode
   TCCR0A = (1<<WGM01);
   //enable output compare 0 A interrupt
   TIMSK |= (1<<OCF0A);
   OCR0A = 103;
}

//timer0 compare A match interrupt
ISR(TIM0_COMPA_vect ){
	uint16_t local_tx_shift_reg = tx_shift_reg;
	if( local_tx_shift_reg & 0x01 ){
		TX_PORT |= (1<<TX_PIN);
	}else{
		TX_PORT &=~ (1<<TX_PIN);
	}
	local_tx_shift_reg >>= 1;
	tx_shift_reg = local_tx_shift_reg;
	if(!local_tx_shift_reg){
		TCCR0B = 0;
		TCNT0 = 0;
	}
}

//Init Internal ADC of CPU
void initADC(void) {
	ADMUX = 0x00;
	ADCSRA = (1<<ADEN) | (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0);
	
	ADCSRA |= (1<<ADSC);
	
	while(ADCSRA & (1<<ADSC)) {
	}
	
	(void)ADCL;
	(void)ADCH;
	
}

//Read Singleend ADC Channel
uint16_t readADC(uint8_t channel) {
//	ADMUX = (0 << 4) | (channel & 0x07);
	ADMUX = (ADMUX & 0xE0) | (channel & 0x1F);
	_delay_ms(1);
	ADCSRA |= (1<<ADSC);
	while(ADCSRA & (1<<ADSC)) {
	}

 	uint8_t low = ADCL;
 	uint8_t high = ADCH;
	
	return ((uint16_t)high << 8) | (uint16_t)low;
	//return ADCW;
}