X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?p=heater.git;a=blobdiff_plain;f=firmware%2Fmain.c;h=76bed47f45f1f70895f4abc25bf1f9588ac8b988;hp=9a041500be8aefd19088472b2aa1ae2d8e50ca9d;hb=d3b9a34d6b153bd04e7d233c2e2bbcecc70a6fa5;hpb=36f60161fac194572a272bdb0239a01fcf2b801b diff --git a/firmware/main.c b/firmware/main.c index 9a04150..76bed47 100644 --- a/firmware/main.c +++ b/firmware/main.c @@ -1,3 +1,51 @@ +/* + * 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 #include #include @@ -7,30 +55,165 @@ #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); - 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; +} + +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); @@ -47,6 +230,12 @@ static void status_led_off() 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 @@ -73,9 +262,6 @@ static unsigned char buttons_pressed() ); } -#define WAKEUP_POLL 100 // msec -#define WAKEUP_LIMIT 5 // times WAKEUP_POLL - static unsigned char buttons_wait_for_release() { uint16_t wake_count = 0; @@ -97,8 +283,11 @@ ISR(PCINT0_vect) // 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 } @@ -107,11 +296,17 @@ static void wdt_susp() 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(); @@ -119,22 +314,15 @@ static void hw_setup() 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(); @@ -158,22 +346,97 @@ static void power_down() 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; @@ -183,8 +446,12 @@ static void timer_check_buttons() 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; } @@ -195,35 +462,58 @@ static void timer_check_buttons() } // 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 @@ -236,9 +526,24 @@ int main() 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(); } } }