/* Soil Sensor Bootloader
 * Main file.
 * Sensiplicity Systems
 * 
 *  Copyright 2015
 * 
 *  Department of Botany and Plant Pathology
 *  Center for Genome Research and Biocomputing
 *  Oregon State University
 *  Corvallis, OR 97331
 * 
 * This program is not free software; you can not redistribute it and/or
 * modify it at all.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. */
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
#include "bus.h"
#include "light.h"
#include "crc.h"
#define F_CPU 2000000l
#include <util/delay.h>
//TODO
#include <avr/eeprom.h>

/* Calling this "function" jumps to the main program. */
void (*start_firmware)(void) = 0x0000;

/* Move interrupt vector table to bootloader space. */
void bl_interrupts(void){
	MCUCR = _BV(IVCE);
	MCUCR = _BV(IVSEL);
}

/* Move interrupt vector to main program space. */
void fw_interrupts(void){
	MCUCR = _BV(IVCE);
	MCUCR = 0;
}

/* Compute an overall CRC of the whole main firmware flash space.
 * A CRC is first computed for each set of six flash pages, then an
 * overall CRC is computed from those. */
uint16_t calc_flash_crc(void){
	uint8_t sixpage_buf[192]; /* Due to the AVR's Harvard architecture, each set of six pages
	                           * must be loaded from Flash into RAM for the CRC routine of
	                           * operate on them. */
	uint16_t sixpage_crcs[32]; /* CRCs of each set of six pages. */
	
	for(uint8_t i=0; i<32; i++){
		for(uint8_t b=0; b<192; b++){
			sixpage_buf[b] = pgm_read_byte_near((i * 192) + b);
		}
		if(31 == i){
			/* Exclude the last two bytes of the last page, 
			 * as they contain the overall CRC. */
			sixpage_crcs[i] = calc_crc(sixpage_buf, 190);
		} else {
			sixpage_crcs[i] = calc_crc(sixpage_buf, 192);
		}
	}
	return calc_crc((uint8_t *) sixpage_crcs, 64);
}
	
int main(void){
	//TODO: For maximum robustness, set lock bits to prevent the
	//bootloader from being modified.
	/* Set system clock to 16MHz/8 = 2MHz */
	CLKPR = _BV(CLKPCE);
	CLKPR = _BV(CLKPS1) | _BV(CLKPS0);
	
	bl_interrupts();
	init_bus();
	init_led();
	
	set_led(LED_GREEN);
	
	uint16_t overall_crc = calc_flash_crc();
	uint16_t stored_crc = pgm_read_word_near(6142);
	if(stored_crc != overall_crc){
		ProgrammingMode = 1;
		set_led(LED_RED);
	}
	
	_delay_ms(500);
	
	if(!ProgrammingMode){
		/* No request to enter programming mode, start the main firmware. */
		cli();
		set_led(LED_OFF);
		fw_interrupts();
		start_firmware();
	} else {
		/* Programming in progress. Loop until rebooted by bus module. */
		while(1);
	}
	
	return 0;
}