keyboard/hhkb_rn42/rn42/battery.c

   1 #include <avr/io.h>
   2 #include <util/delay.h>
   3 #include "battery.h"
   4
   5
   6 /*
   7  * Battery
   8  */
   9 void battery_init(void)
  10 {
  11     // blink
  12     battery_led(LED_ON);  _delay_ms(500);
  13     battery_led(LED_OFF); _delay_ms(500);
  14     battery_led(LED_ON);  _delay_ms(500);
  15     battery_led(LED_OFF); _delay_ms(500);
  16     // LED indicates charger status
  17     battery_led(LED_CHARGER);
  18
  19     // ADC setting for voltage monitor
  20     // Ref:2.56V band-gap, Input:ADC0(PF0), Prescale:128(16MHz/128=125KHz)
  21     ADMUX = (1<<REFS1) | (1<<REFS0);
  22     ADCSRA = (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0);
  23     ADCSRA |= (1<<ADEN);
  24 }
  25
  26 // Indicator for battery
  27 void battery_led(battery_led_t val)
  28 {
  29     if (val == LED_TOGGLE) {
  30         // Toggle LED
  31         DDRF  |=  (1<<5);
  32         PINF  |=  (1<<5);
  33     } else if (val == LED_ON) {
  34         // On overriding charger status
  35         DDRF  |=  (1<<5);
  36         PORTF &= ~(1<<5);
  37     } else if (val == LED_OFF) {
  38         // Off overriding charger status
  39         DDRF  |=  (1<<5);
  40         PORTF |=  (1<<5);
  41     } else {
  42         // Display charger status
  43         DDRF  &= ~(1<<5);
  44         PORTF &= ~(1<<5);
  45     }
  46 }
  47
  48 bool battery_charging(void)
  49 {
  50     if (!(USBSTA&(1<<VBUS))) return false;
  51
  52     // MCP73831:STAT
  53     //   HiZ:    Shutdown/No Battery
  54     //   Low:    Charging
  55     //   Hi:     Charged
  56
  57     // preserve last register status
  58     uint8_t ddrf_prev  = DDRF;
  59     uint8_t portf_prev = PORTF;
  60
  61     // Input with pullup
  62     DDRF  &= ~(1<<5);
  63     PORTF |=  (1<<5);
  64     _delay_ms(1);
  65     bool charging = PINF&(1<<5) ? false : true;
  66
  67     // restore last register status
  68     DDRF  = (DDRF&~(1<<5))  | (ddrf_prev&(1<<5));
  69     PORTF = (PORTF&~(1<<5)) | (portf_prev&(1<<5));
  70
  71     return charging;
  72 }
  73
  74 // Returns voltage in mV
  75 uint16_t battery_voltage(void)
  76 {
  77     volatile uint16_t bat;
  78     //ADCSRA |= (1<<ADEN);
  79
  80     // discard first result
  81     ADCSRA |= (1<<ADSC);
  82     while (ADCSRA & (1<<ADSC)) ;
  83     bat = ADC;
  84
  85     // discard second result
  86     ADCSRA |= (1<<ADSC);
  87     while (ADCSRA & (1<<ADSC)) ;
  88     bat = ADC;
  89
  90     ADCSRA |= (1<<ADSC);
  91     while (ADCSRA & (1<<ADSC)) ;
  92     bat = ADC;
  93
  94     //ADCSRA &= ~(1<<ADEN);
  95
  96     return (bat - BATTERY_ADC_OFFSET) * BATTERY_ADC_RESOLUTION;
  97 }
  98
  99 static bool low_voltage(void) {
 100     static bool low = false;
 101     uint16_t v = battery_voltage();
 102     if (v < BATTERY_VOLTAGE_LOW_LIMIT) {
 103         low = true;
 104     } else if (v > BATTERY_VOLTAGE_LOW_RECOVERY) {
 105         low = false;
 106     }
 107     return low;
 108 }
 109
 110 battery_status_t battery_status(void)
 111 {
 112     if (USBSTA&(1<<VBUS)) {
 113         /* powered */
 114         return battery_charging() ? CHARGING : FULL_CHARGED;
 115     } else {
 116         /* not powered */
 117         return low_voltage() ? LOW_VOLTAGE : DISCHARGING;
 118     }
 119 }