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--- info:feb_2014_bms_using_avr [2014/02/10 15:13] – created tomgee
+++ info:feb_2014_bms_using_avr [2014/02/10 15:14] (current) – tomgee
@@ Line 9: / Line 9: @@
 {{:info:bms_diy_schematic_labeled.gif|}}
 {{:info:diy_bms_img.jpg|}}
-     // 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;
-	}
-}