+/*
+ * OVERVIEW
+ *
+ * Powering up:
+ * Immediately after reset, we power down the entire system.
+ * We wake up only after the button is pressed for a sufficiently long time.
+ *
+ * Heater output:
+ * The heater output is driven by Timer/Counter 1 in PWM mode.
+ * We want to be able to measure the battery voltage both when the
+ * output is on, and when the output is off. So we set the T/C1 clock
+ * prescaler so that the T/C1 is slow enough, we enable the T/C1 interrupts
+ * both on compare match and on overflow. After the interrupt, we trigger
+ * the battery voltage measurement with ADC.
+ *
+ * ADC:
+ * To avoid transients, we measure each battery state (when the heater is on
+ * and when it is off) separately, and we drop the first few readings.
+ * We calculate a running average of the readings to achieve higher accuracy.
+ *
+ * Buttons:
+ * There are two buttons (+ and -). Any button can wake the system up from
+ * the power-down state.
+ * TODO: When the system is woken up by the "-" button,
+ * it starts with the minimum output power, when it is woken up by the "+"
+ * button, it start with the maximum output power.
+ * When running, the "-" button is used for decreasing the output power,
+ * the "+" button is for increasing it.
+ * When on the lowest power state, the "-" button switches the system off.
+ * Long "-" button press switches the system off, long "+" button
+ * press sets the output power to maximum.
+ *
+ * Status LED:
+ * When powering up by a button press, the LED goes on to provide a visual
+ * feedback, and is switched off after the button is released.
+ * After a button press, the # of blinks of the LED reflects the
+ * chosen output power level for some time. Afterwards, it displays
+ * the battery level.
+ * When the battery is completely exhausted, the output power is switched
+ * off, the LED keeps blinking for some time, and then the whole system is
+ * switched off to avoid deep discharge of the battery.
+ *
+ * Timing:
+ * The firmware is timed by the Watchdog Timer interrupt. Most of the
+ * processing is done from the main loop, IRQs only set various flags
+ * or trigger other events.
+ */
+
#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/power.h>
#include "logging.h"
-static unsigned char pwm = 1;
+/* waking up from the power down state by a button press */
+#define WAKEUP_POLL 50 // msec
+#define WAKEUP_LIMIT 5 // times WAKEUP_POLL
+
+/* which state (output on or output off) are we measuring now */
+static volatile unsigned char adc_type, adc_drop;
+#define ADC_RUNAVG_SHIFT 5 // running average shift on batt_on, batt_off
+static volatile uint16_t batt_on, batt_off; // measured voltage
+
+/*
+ * The voltage divider has 1M5 and 300K resistors (i.e. it measures 1/6th of
+ * the real voltage), ADC uses 1.1V internal reference.
+ * Macro to calculate upper eight bits of the ADC running-averaged value
+ * from the voltage in milivolts.
+ */
+#define ADC_1100MV_VALUE 1071 // measured, not exactly 1100
+#define MV_TO_ADC8(mV) ((unsigned char)(((uint32_t)(1UL << ADC_RUNAVG_SHIFT) \
+ * (1024UL * (mV)) \
+ / (6UL * ADC_1100MV_VALUE)) >> 8))
+static unsigned char batt_levels[] = {
+ MV_TO_ADC8(3350),
+ MV_TO_ADC8(3700),
+ MV_TO_ADC8(3900),
+};
+#define BATT_N_LEVELS (sizeof(batt_levels) / sizeof(batt_levels[0]))
+
+/* output power and PWM calculation */
+#define PWM_TOP 255
+#define PWM_MAX (PWM_TOP - 8) // to allow for ADC "batt_off" measurements
+
+/*
+ * The values in power_levels[] array are voltages at which the load
+ * would give the expected power (we don't have sqrt() function,
+ * so we cannot use mW values directly. They can be calculated as
+ * voltage[V] = sqrt(load_resistance[Ohm] * expected_power[W])
+ * or
+ * voltage[mV] = sqrt(load_resistance[mOhm] * expected_power[mW])
+ *
+ * I use 1.25 W as minimum power, each step is sqrt(2)*previous_step,
+ * so the 5th step is 5 W.
+ */
+static unsigned char power_levels[] = {
+ MV_TO_ADC8(1581), // 1250 mW for 2 Ohm load
+ MV_TO_ADC8(1880), // 1768 mW for 2 Ohm load
+ MV_TO_ADC8(2236), // 2500 mW for 2 Ohm load
+ MV_TO_ADC8(2659), // 3536 mW for 2 Ohm load
+ MV_TO_ADC8(3162), // 5000 mW for 2 Ohm load
+};
+#define N_POWER_LEVELS (sizeof(power_levels) / sizeof(power_levels[0]))
+
+static unsigned char power_level = 0; // selected power level
+static unsigned char power_level_changed; // for visual feedback
+
+#define LED_PWRCHANGE_COUNT 3
+#define LED_BATTEMPTY_COUNT 60
+
+/* timing by WDT */
+static volatile unsigned char jiffies, next_clock_tick;
+
+/* button press duration (in jiffies) */
+#define BUTTON_SHORT_MIN 1
+#define BUTTON_LONG_MIN 10
+
+
+/* ========= Analog to Digital Converter (battery voltage) ========== */
+static void adc_init()
+{
+ power_adc_enable();
+
+ ADCSRA = _BV(ADEN) // enable
+ | _BV(ADPS1) | _BV(ADPS0) // clk/8 = 125 kHz
+ | _BV(ADIE); // enable IRQ
+ ADMUX = _BV(REFS1) | _BV(MUX1) | _BV(MUX0);
+ // 1.1V reference, PB3 pin, single-ended
+ DIDR0 |= _BV(ADC3D); // PB3 pin as analog input
+}
+
+static void adc_susp()
+{
+ ADCSRA &= ~_BV(ADEN); // disable ADC
+ DIDR0 &= ~_BV(ADC3D); // disable analog input on PB3
+
+ power_adc_disable();
+}
+
+static void adc_start_measurement()
+{
+ ADCSRA |= _BV(ADSC);
+}
+
+ISR(ADC_vect)
+{
+ uint16_t adcw = ADCW;
+
+ if (adc_drop) {
+ adc_drop--;
+ ADCSRA |= _BV(ADSC);
+ return;
+ }
+
+ // TODO: We may want to disable ADC after here to save power,
+ // but compared to the heater power it would be negligible,
+ // so don't bother with it.
+ if (adc_type == 0) {
+ if (batt_off) {
+ batt_off += adcw - (batt_off >> ADC_RUNAVG_SHIFT);
+ } else {
+ batt_off = adcw << ADC_RUNAVG_SHIFT;
+ }
+ } else {
+ if (batt_on) {
+ batt_on += adcw - (batt_on >> ADC_RUNAVG_SHIFT);
+ } else {
+ batt_on = adcw << ADC_RUNAVG_SHIFT;
+ }
+ }
+}
-static void timer_init()
+/* ===================== Timer/Counter1 for PWM ===================== */
+static void pwm_init()
{
power_timer1_enable();
DDRB |= _BV(PB4);
+ PORTB &= ~_BV(PB4);
- TCCR1 = _BV(CS10); // clk/1 = 1 MHz
- // TCCR1 = _BV(CS11) | _BV(CS13); // clk/512 = 2 kHz
+ // TCCR1 = _BV(CS10); // clk/1 = 1 MHz
+ TCCR1 = _BV(CS11) | _BV(CS13); // clk/512 = 2 kHz
GTCCR = _BV(COM1B1) | _BV(PWM1B);
- OCR1C = 255;
- OCR1B = pwm;
+ OCR1C = PWM_TOP;
+ // OCR1B = steps[0];
+ OCR1B = 0;
+ TIMSK = _BV(OCIE1B) | _BV(TOIE1);
}
-static void adc_init()
+static void pwm_susp()
{
- power_adc_enable();
+ TCCR1 = 0;
+ TIMSK = 0;
+ GTCCR = 0;
+ PORTB &= ~_BV(PB4);
+}
+
+ISR(TIM1_OVF_vect)
+{
+ adc_drop = 2;
+ adc_type = 1;
+ adc_start_measurement();
+}
+
+ISR(TIM1_COMPB_vect)
+{
+ adc_drop = 2;
+ adc_type = 0;
+ adc_start_measurement();
+}
- ADCSRA = _BV(ADEN) | _BV(ADPS1) | _BV(ADPS0); // clk/8 = 125 kHz
- ADMUX = _BV(REFS1) | _BV(MUX1) | _BV(MUX0); // 1.1V ref., PB3 single-ended
- DIDR0 = _BV(ADC3D);
+static void pwm_set(unsigned char pwm)
+{
+ OCR1B = pwm;
}
+/* ===================== Status LED on pin PB2 ======================= */
static void status_led_init()
{
DDRB |= _BV(PB2);
PORTB &= ~_BV(PB2);
}
+static unsigned char status_led_is_on()
+{
+ return PORTB & _BV(PB2) ? 1 : 0;
+}
+
+/* ================== Buttons on pin PB0 and PB1 ===================== */
static void buttons_init()
{
DDRB &= ~(_BV(PB0) | _BV(PB1)); // set as input
);
}
-#define WAKEUP_POLL 100 // msec
-#define WAKEUP_LIMIT 5 // times WAKEUP_POLL
-
static unsigned char buttons_wait_for_release()
{
uint16_t wake_count = 0;
// empty - let it wake us from sleep, but do nothing else
}
+/* ==== Watchdog Timer for timing blinks and other periodic tasks ==== */
static void wdt_init()
{
+ next_clock_tick = 0;
+ jiffies = 0;
WDTCR = _BV(WDIE) | _BV(WDP1); // interrupt mode, 64 ms
}
wdt_disable();
}
+ISR(WDT_vect) {
+ next_clock_tick = 1;
+ jiffies++;
+}
+
+/* ====== Hardware init, teardown, powering down and waking up ====== */
static void hw_setup()
{
power_all_disable();
- timer_init();
+ pwm_init();
adc_init();
status_led_init();
wdt_init();
static void hw_suspend()
{
- ADCSRA &= ~_BV(ADEN); // disable ADC
- TCCR1 = 0; // disable T/C 1
-
- status_led_init();
+ adc_susp();
+ pwm_susp();
+ status_led_init(); // we don't have a separate _susp() here
buttons_susp();
wdt_susp();
power_all_disable();
}
-static volatile unsigned char wdt_timer_fired;
-
-ISR(WDT_vect) {
- wdt_timer_fired = 1;
-}
-
static void power_down()
{
hw_suspend();
hw_setup();
}
-static void button_one_pressed()
+/* ============ Status LED blinking =================================== */
+static unsigned char blink_on_time, blink_off_time, n_blinks;
+static unsigned char blink_counter;
+
+static unsigned char battery_level()
+{
+ unsigned char i, adc8;
+
+ // NOTE: we use 8-bit value only, so we don't need lock to protect
+ // us against concurrently running ADC IRQ handler:
+ adc8 = batt_off >> 8;
+
+ for (i = 0; i < BATT_N_LEVELS; i++)
+ if (batt_levels[i] > adc8)
+ break;
+
+ return i;
+}
+
+static void status_led_next_pattern()
{
- if (pwm > 1) {
- pwm >>= 1;
- OCR1B = pwm;
+ static unsigned char battery_exhausted;
+
+ if (power_level_changed) {
+ power_level_changed--;
+ n_blinks = power_level + 1;
+ } else {
+ unsigned char b_level = battery_level();
+ if (b_level) {
+ battery_exhausted = 0;
+ } else if (battery_exhausted) {
+ if (!--battery_exhausted)
+ power_down();
+ } else {
+ battery_exhausted = LED_BATTEMPTY_COUNT;
+ }
+
+ n_blinks = b_level + 1;
+ }
+
+ blink_on_time = 2;
+ blink_off_time = 1;
+ blink_counter = 10;
+}
+
+static void timer_blink()
+{
+ if (blink_counter) {
+ blink_counter--;
+ } else if (!status_led_is_on()) {
+ status_led_on();
+ blink_counter = blink_on_time;
+ } else if (n_blinks) {
+ --n_blinks;
+ status_led_off();
+ blink_counter = blink_off_time;
} else {
- power_down();
+ status_led_next_pattern();
}
}
-static void button_two_pressed()
+/* ======== Button press detection and handling ===================== */
+static void button_pressed(unsigned char button, unsigned char long_press)
{
- if (pwm < 0x80) {
- pwm <<= 1;
- OCR1B = pwm;
+ // ignore simlultaneous button 1 and 2 press
+ // Note: we set power_level_changed after each button press,
+ // even when the power is at maximum, to provide visual feedback
+ // with status LED.
+ if (long_press) {
+ if (button == 1) {
+ power_down();
+ return;
+ } else if (button == 2) {
+ power_level = N_POWER_LEVELS-1;
+ }
+ } else { // short press
+ if (button == 1) {
+ if (power_level > 0) {
+ --power_level;
+ } else {
+ power_down();
+ return;
+ }
+ } else if (button == 2) {
+ if (power_level < N_POWER_LEVELS-1) {
+ ++power_level;
+ }
+ }
}
+ power_level_changed = LED_PWRCHANGE_COUNT;
+ status_led_next_pattern();
}
static unsigned char button_state, button_state_time;
unsigned char newstate = buttons_pressed();
if (newstate == button_state) {
- if (newstate && button_state_time < 4)
+ if (newstate && button_state_time < BUTTON_LONG_MIN)
++button_state_time;
+
+ if (newstate && button_state_time >= BUTTON_LONG_MIN) {
+ status_led_on();
+ }
return;
}
}
// just released
- switch (button_state) {
- case 1: button_one_pressed();
- break;
- case 2: button_two_pressed();
- break;
- default: // ignore when both are preseed
- break;
- }
+ if (button_state_time >= BUTTON_SHORT_MIN)
+ button_pressed(button_state,
+ button_state_time >= BUTTON_LONG_MIN ? 1 : 0);
button_state = newstate;
+ button_state_time = 0;
+}
+
+/* ===================== Output power control ======================== */
+static void calculate_power_level()
+{
+ uint32_t pwm;
+ unsigned char batt_on8;
+
+ if (battery_level() == 0 || batt_on == 0) {
+ pwm_set(0);
+ // TODO power_down() after some time
+ return;
+ }
+
+ batt_on8 = batt_on >> 8;
+
+ pwm = (uint32_t)PWM_TOP * power_levels[power_level]
+ * power_levels[power_level];
+ pwm /= (uint32_t)batt_on8 * batt_on8;
+
+ if (pwm > PWM_MAX)
+ pwm = PWM_MAX;
+
+ log_byte(0x10 + power_level);
+ log_byte(batt_on8);
+ log_byte(pwm & 0xFF);
+
+ pwm_set(pwm);
}
int main()
{
log_init();
- power_down();
-
#if 0
- ADCSRA |= _BV(ADSC);
- while (!(ADCSRA & _BV(ADIF)))
- ;
- log_word(ADCW);
- ADCSRA |= _BV(ADSC);
- while (!(ADCSRA & _BV(ADIF)))
- ;
- log_word(ADCW);
+ log_word(batt_levels[0]);
+ log_word(batt_levels[1]);
+ log_word(batt_levels[2]);
log_flush();
#endif
+ log_byte(power_levels[0]);
+ log_byte(power_levels[4]);
+ log_flush();
+
+ power_down();
+
sei();
// we try to be completely IRQ-driven, so just wait for IRQs here
sleep_cpu();
sleep_disable();
- if (wdt_timer_fired) {
- wdt_timer_fired = 0;
+ // FIXME: Maybe handle new ADC readings as well?
+ if (next_clock_tick) {
+ next_clock_tick = 0;
+ timer_blink();
+ // this has to be after the timer_blink() call
+ // to override the status LED during long button press
timer_check_buttons();
+
+ if ((jiffies & 0x0F) == 0) {
+ calculate_power_level();
+#if 0
+ log_byte(0xcc);
+ log_byte(i);
+ log_byte(batt_off >> 8);
+ log_byte(batt_on >> 8);
+#endif
+ }
+ log_flush();
}
}
}
https://www.fi.muni.cz/~kas/git / heater.git / blobdiff