Low battery bugfix:
[heater.git] / firmware / main.c
index ddbd2d3..65801e8 100644 (file)
  * 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.
- * TODO: Long "-" button press switches the system off, long "+" button
- * press sets the output power to maximum.
+ * Any long button press switches the system off.
  *
  * 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.
- * TODO: 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.
- * TODO: When the battery is completely exhausted, the output power is switched
+ * It displays the current power level and current battery voltage
+ * using # of blinks with different blinking lengths.
+ * 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.
  *
 #define WAKEUP_POLL 50 // msec
 #define WAKEUP_LIMIT 5 // times WAKEUP_POLL
 
-/* output power levels */
-#define N_STEPS 5
-static unsigned char steps[] = { 60, 85, 121, 171, 242 };
-static unsigned char intensity = 0; // selected power level
+// #define BUTTONS_REVERSE
+
+#ifdef BUTTONS_REVERSE
+#      define BUTTON1  PB0
+#      define BUTTON2  PB1
+#else
+#      define BUTTON1  PB1
+#      define BUTTON2  PB0
+#endif /* !BUTTONS_REVERSE */
 
 /* 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(3000), // below this, do not enable load, and switch off
+       MV_TO_ADC8(3150), // below this, switch off after some time
+       MV_TO_ADC8(3450), // battery low
+       MV_TO_ADC8(3800), // battery ok, above that almost full
+};
+#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
+#define PWM_MIN        8               // to allow for ADC "batt_on" 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
+
+#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
+       ADCSRA = _BV(ADEN)                      // enable
+               | _BV(ADPS1) | _BV(ADPS0);      // clk/8 = 125 kHz
        ADMUX = _BV(REFS1) | _BV(MUX1) | _BV(MUX0);
                // 1.1V reference, PB3 pin, single-ended
        DIDR0 |= _BV(ADC3D);    // PB3 pin as analog input
@@ -86,15 +137,17 @@ static void adc_init()
 
 static void adc_susp()
 {
-       ADCSRA &= ~_BV(ADEN);   // disable ADC
+       ADCSRA = 0;             // disable ADC
        DIDR0 &= ~_BV(ADC3D);   // disable analog input on PB3
 
        power_adc_disable();
 }
 
-static void adc_start_measurement()
+static void adc_start_measurement(unsigned char on)
 {
-       ADCSRA |= _BV(ADSC);
+       adc_drop = 1;
+       adc_type = on;
+       ADCSRA |= _BV(ADSC) | _BV(ADIE);
 }
 
 ISR(ADC_vect)
@@ -112,17 +165,18 @@ ISR(ADC_vect)
        // so don't bother with it.
        if (adc_type == 0) {
                if (batt_off) {
-                       batt_off += adcw - (batt_off >> 5);
+                       batt_off += adcw - (batt_off >> ADC_RUNAVG_SHIFT);
                } else {
-                       batt_off = adcw << 5;
+                       batt_off = adcw << ADC_RUNAVG_SHIFT;
                }
        } else {
                if (batt_on) {
-                       batt_on += adcw - (batt_on >> 5);
+                       batt_on += adcw - (batt_on >> ADC_RUNAVG_SHIFT);
                } else {
-                       batt_on = adcw << 5;
+                       batt_on = adcw << ADC_RUNAVG_SHIFT;
                }
        }
+       ADCSRA &= ~_BV(ADIE);
 }
 
 /* ===================== Timer/Counter1 for PWM ===================== */
@@ -131,32 +185,41 @@ 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(CS11) | _BV(CS13); // clk/512 = 2 kHz
+       /*
+        * clk/64 = 16 kHz. We use PWM_MIN and PWM_MAX, so we have at least
+        * 8 full T/C1 cycles to do two ADC measurements. The ADC with 125 kHz
+        * clock can do about 7000-9000 measurement per second, so we should
+        * be safe both on low and high OCR1B values with this clock
+        */
+       TCCR1 = _BV(CS12) | _BV(CS11) | _BV(CS10);
+
        GTCCR = _BV(COM1B1) | _BV(PWM1B);
-       OCR1C = 255;
-       OCR1B = steps[0];
+       OCR1C = PWM_TOP;
+       // OCR1B = steps[0];
+       OCR1B = 0;
        TIMSK = _BV(OCIE1B) | _BV(TOIE1);
 }
 
 static void pwm_susp()
 {
        TCCR1 = 0;
+       TIMSK = 0;
+       GTCCR = 0;
+       PORTB &= ~_BV(PB4);
 }
 
 ISR(TIM1_OVF_vect)
 {
-       adc_drop = 2;
-       adc_type = 1;
-       adc_start_measurement();
+       adc_start_measurement(1);
 }
 
 ISR(TIM1_COMPB_vect)
 {
-       adc_drop = 2;
-       adc_type = 0;
-       adc_start_measurement();
+       adc_start_measurement(0);
 }
 
 static void pwm_set(unsigned char pwm)
@@ -207,9 +270,9 @@ static void buttons_susp()
 static unsigned char buttons_pressed()
 {
        return (
-               (PINB & _BV(PB0) ? 0 : 1)
+               (PINB & _BV(BUTTON1) ? 0 : 1)
                |
-               (PINB & _BV(PB1) ? 0 : 2)
+               (PINB & _BV(BUTTON2) ? 0 : 2)
        );
 }
 
@@ -297,21 +360,95 @@ static void power_down()
        hw_setup();
 }
 
-/* ======== Button press detection and  handling ===================== */
-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 (intensity > 0) {
-               pwm_set(steps[--intensity]);
+       static unsigned char battery_exhausted;
+       static unsigned char display_power_level;
+
+       if (display_power_level) {
+               n_blinks = power_level + 1;
+               if (batt_on >> 8 == batt_off >> 8) { // load unplugged
+                       n_blinks = 2 * n_blinks;
+                       blink_on_time = 0;
+                       blink_off_time = 0;
+               } else {
+                       blink_on_time = 2;
+                       blink_off_time = 2;
+               }
        } else {
-               power_down();
+               unsigned char b_level = battery_level();
+               if (b_level > 1) {
+                       battery_exhausted = 0;
+               } else if (battery_exhausted) {
+                       if (!--battery_exhausted)
+                               power_down();
+               } else {
+                       battery_exhausted = LED_BATTEMPTY_COUNT;
+               }
+
+               n_blinks = b_level ? b_level : 1;
+               blink_on_time = b_level ? 4 : 2;
+               blink_off_time = 0;
+       }
+
+       blink_counter = 12;
+       display_power_level = !display_power_level;
+}
+
+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 {
+               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 (intensity < N_STEPS-1) {
-               pwm_set(steps[++intensity]);
+       // ignore simlultaneous button 1 and 2 press
+       if (long_press) {
+               power_down();
+               return;
+       } else { // short press
+               if (button == 1) {
+                       if (power_level > 0) {
+                               --power_level;
+                       }
+               } else if (button == 2) {
+                       if (power_level < N_POWER_LEVELS-1) {
+                               ++power_level;
+                       }
+               }
        }
+       status_led_next_pattern();
 }
 
 static unsigned char button_state, button_state_time;
@@ -321,8 +458,12 @@ 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;
        }
 
@@ -333,51 +474,65 @@ 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;
 }
 
-/* ============ Status LED blinking =================================== */
-static unsigned char blink_on_time, blink_off_time, n_blinks;
-static unsigned char blink_counter;
-
-static void status_led_next_pattern()
+/* ===================== Output power control ======================== */
+static void calculate_power_level()
 {
-       // for now, display the selected intensity
-       n_blinks = intensity + 1;
-       blink_on_time = 0;
-       blink_off_time = 2;
-       blink_counter = 10;
-}
+       uint32_t pwm;
+       unsigned char batt_on8;
 
-static void timer_blink()
-{
-       if (blink_counter) {
-               blink_counter--;
-       } else if (status_led_is_on()) {
-               status_led_off();
-               blink_counter = blink_off_time;
-       } else if (n_blinks) {
-               --n_blinks;
-               status_led_on();
-               blink_counter = blink_on_time;
-       } else {
-               status_led_next_pattern();
+       if (battery_level() == 0) {
+               pwm_set(0);
+               // TODO power_down() after some time
+               return;
        }
+
+       if (!batt_on) {
+               batt_on = batt_off;
+       };
+
+       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;
+
+       if (pwm < PWM_MIN)
+               pwm = PWM_MIN;
+
+#if 0
+       log_byte(0x10 + power_level);
+       log_byte(batt_on8);
+       log_byte(pwm & 0xFF);
+#endif
+
+       pwm_set(pwm);
 }
 
 int main()
 {
        log_init();
 
+#if 0
+       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();
@@ -395,8 +550,24 @@ int main()
                // FIXME: Maybe handle new ADC readings as well?
                if (next_clock_tick) {
                        next_clock_tick = 0;
-                       timer_check_buttons();
                        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
+                       }
+                       if (jiffies == 0) {
+                               log_byte(batt_on >> 8);
+                               log_byte(batt_off >> 8);
+                       }
                        log_flush();
                }
        }