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===== AVR BMS =====
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     // 8-cell Lithium BMS module
// Code for ATmega16A
// by Ian Hooper, (C) ZEVA 2012

// Fuses: 1Mhz clock, JTAGEN disabled
// And brown-out at 4 volts to help with the eeprom?

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

#define	ADC_VREF_TYPE	0x40 // AVCC, with capacitor between AREF and GND

// division of 10K high : 1.5K low = 0.130 scaling factor
// 1V full -> 0.13V scaled -> ADC 26.60 per volt
// or, 37.435mV per ADC step
#define LV_THRESHOLD	66 // ~2.5V
#define SHUNT_THRESHOLD	96 // ~3.6V
#define HV_THRESHOLD	106 // ~4.0V

#define TEMP_THRESHOLD	350 // ~1.75V on the ADC, hopefully about 50 degrees

#define	HV_SIG		(1<<PD4)
#define LV_SIG		(1<<PD3)
#define	SHUNT_SIG	(1<<PD2)

#define TEMP1_IN	(1<<PB1);
#define	TEMP2_IN	(1<<PB0);

// HV sample enable pins
//	1	2	3	4	5	6	7	8
//	PD6	PC0	PC2	PC4	PC6	PA7	PA5	PA3

// Shunt enable pins
//	1	2	3	4	5	6	7	8
//	PD5	PD7	PC1	PC3	PC5	PC7	PA6	PA4

// Status LED outputs
//	1	2	3	4	5	6	7	8
//	PB7	PB6	PB5	PB4	PB3	PB2	PB1	PB0

#ifndef true
	#define true	1
	#define false	0
#endif

// Function declarations
void SetupPorts();
int GetCell(int n); // 0-8
void SetShunt(int n, char state);
void SetLED(int n, char state);

// Global variables
int level[9];
char lows[9];
char highs[9];
char shunts[9];
char temps[2];

unsigned char counter;

unsigned short ReadADC(unsigned char adc_input)
{
	ADMUX=adc_input | (ADC_VREF_TYPE & 0xff);
	_delay_us(10); // Delay needed for the stabilization of the ADC input voltage
	ADCSRA|=0x40; // Start the AD conversion
	while ((ADCSRA & 0x10)==0); // Wait for the AD conversion to complete
	ADCSRA|=0x10;
	return ADCW;
}

int main(void)
{
	SetupPorts();
	wdt_enable(WDTO_250MS);

level[0] = -16; // Fixed reference point
	// Opto has a ~0.6V forward drop?
	// 37mV per step -> 16 extra needed for level zero

while (1)
	{
		wdt_reset();
		counter++;
		
		for (int n=1; n<=8; n++)
			level[n] = GetCell(n);
		GetCell(0); // Turn sampling off

for (int n=1; n<=8; n++)
		{
			int diff = level[n] - level[n-1];
			
			// Tiny bit of hysteresis around the threshold value
			if (diff < LV_THRESHOLD)
				lows[n] = true;
			else if (diff > LV_THRESHOLD)
				lows[n] = false;

if (diff > HV_THRESHOLD)
				highs[n] = true;
			else if (diff < HV_THRESHOLD)
				highs[n] = false;

if (diff > SHUNT_THRESHOLD)
				shunts[n] = true;
			else if (diff < SHUNT_THRESHOLD)
				shunts[n] = false;
			SetShunt(n, shunts[n]);
			
			if (lows[n] || highs[n])
				SetLED(n, false);		// LED off
			else if (shunts[n])
				SetLED(n, counter&1); // blink
			else
				SetLED(n, true); // Constant on = no errors
			
		}

char low = false;
		char high = false;
		char shunt = false;
		for (int n=1; n<=8; n++)
		{
			if (lows[n]) low = true;
			if (highs[n]) high = true;
			if (shunts[n]) shunt = true;
		}

// Temperatures, ADC0 = Temp2, ADC1 = Temp1
		// Altronics thermistor is about 10K at room temp, i.e ADC 512 will be room temp
		// Voltage goes DOWN as it gets hotter
		// 0.68V is about 80degC - TOO HOT
		// 1.6V is about 45degC - bit hotter is fine
		// I'm thinking about 1V would be ~60degC which is a good upper limit for shunts and batteries
		for (int n=0; n<2; n++)
		{
			if (ReadADC(n) < TEMP_THRESHOLD-10)
				temps[n] = true;
			else if (ReadADC(n) > TEMP_THRESHOLD+10)
				temps[n] = false;
		}

if (temps[0] || temps[1])
		{	low = true; high = true; } // Shut down both charge and drive

// Reverse logic, so it holds a daisy chain closed whenever all modules are happy
		if (low)	PORTD &= ~LV_SIG; else PORTD |= LV_SIG;;
		if (high)	PORTD &= ~HV_SIG; else PORTD |= HV_SIG;
		if (shunt)	PORTD &= ~SHUNT_SIG; else PORTD |= SHUNT_SIG;
		
		_delay_ms(100); // slow iterations down a little, slightly dirty coding
	}
}

void SetupPorts()
{
	// I/O direction registers; 0 means input, 1 means output
    DDRA = 0b11111000;
	DDRB = 0b11111111;
	DDRC = 0b11111111;
	DDRD = 0b11111100;

ADCSRA = 0b10000011; // ADC clock prescaler is /8 with 011 as final bits, ADC clock should be between 50khz and 200khz and we're running 1Mhz uC clock
}

int GetCell(int n)
{
	// Turn all HV sampler pins off
	PORTA &= ~0b10101000;
	PORTC &= ~0b01010101;
	PORTD &= ~0b01000000;

switch (n) // Turn selected sampler on
	{
		case 1: PORTD |= (1<<PD6); break;
		case 2: PORTC |= (1<<PC0); break;
		case 3: PORTC |= (1<<PC2); break;
		case 4: PORTC |= (1<<PC4); break;
		case 5: PORTC |= (1<<PC6); break;
		case 6: PORTA |= (1<<PA7); break;
		case 7: PORTA |= (1<<PA5); break;
		case 8: PORTA |= (1<<PA3); break;
		default: return 0;
	}

_delay_ms(1); // Allow filter capacitor to stabilise
	return ReadADC(2); // TODO: We may need to acount for optotransistor voltage drop here too
}

void SetShunt(int n, char state) // state should be on or off / true or false
{
	switch (n)
	{
		case 1: if (state) PORTD |= (1<<PD5); else PORTD &= ~(1<<PD5); break;
		case 2: if (state) PORTD |= (1<<PD7); else PORTD &= ~(1<<PD7); break;
		case 3: if (state) PORTC |= (1<<PC1); else PORTC &= ~(1<<PC1); break;
		case 4: if (state) PORTC |= (1<<PC3); else PORTC &= ~(1<<PC3); break;
		case 5: if (state) PORTC |= (1<<PC5); else PORTC &= ~(1<<PC5); break;
		case 6: if (state) PORTC |= (1<<PC7); else PORTC &= ~(1<<PC7); break;
		case 7: if (state) PORTA |= (1<<PA6); else PORTA &= ~(1<<PA6); break;
		case 8: if (state) PORTA |= (1<<PA4); else PORTA &= ~(1<<PA4); break;
	}
}

void SetLED(int n, char state) // state should be on or off / true or false
{
	switch (n) // TODO: faster algorithm
	{
		case 1: if (state) PORTB |= (1<<PB7); else PORTB &= ~(1<<PB7); break;
		case 2: if (state) PORTB |= (1<<PB6); else PORTB &= ~(1<<PB6); break;
		case 3: if (state) PORTB |= (1<<PB5); else PORTB &= ~(1<<PB5); break;
		case 4: if (state) PORTB |= (1<<PB4); else PORTB &= ~(1<<PB4); break;
		case 5: if (state) PORTB |= (1<<PB3); else PORTB &= ~(1<<PB3); break;
		case 6: if (state) PORTB |= (1<<PB2); else PORTB &= ~(1<<PB2); break;
		case 7: if (state) PORTB |= (1<<PB1); else PORTB &= ~(1<<PB1); break;
		case 8: if (state) PORTB |= (1<<PB0); else PORTB &= ~(1<<PB0); break;
	}
}

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