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     // ADC disable voltate divider(PF4)
  26     DDRF  |=  (1<<4);
  27     PORTF &= ~(1<<4);
  28 }
  29
  30 // Indicator for battery
  31 void battery_led(battery_led_t val)
  32 {
  33     if (val == LED_TOGGLE) {
  34         // Toggle LED
  35         DDRF  |=  (1<<5);
  36         PINF  |=  (1<<5);
  37     } else if (val == LED_ON) {
  38         // On overriding charger status
  39         DDRF  |=  (1<<5);
  40         PORTF &= ~(1<<5);
  41     } else if (val == LED_OFF) {
  42         // Off overriding charger status
  43         DDRF  |=  (1<<5);
  44         PORTF |=  (1<<5);
  45     } else {
  46         // Display charger status
  47         DDRF  &= ~(1<<5);
  48         PORTF &= ~(1<<5);
  49     }
  50 }
  51
  52 bool battery_charging(void)
  53 {
  54     if (!(USBSTA&(1<<VBUS))) return false;
  55
  56     // Charger Status:
  57     //   MCP73831   MCP73832   LTC4054  Status
  58     //   Hi-Z       Hi-Z       Hi-Z     Shutdown/No Battery
  59     //   Low        Low        Low      Charging
  60     //   Hi         Hi-Z       Hi-Z     Charged
  61
  62     // preserve last register status
  63     uint8_t ddrf_prev  = DDRF;
  64     uint8_t portf_prev = PORTF;
  65
  66     // Input with pullup
  67     DDRF  &= ~(1<<5);
  68     PORTF |=  (1<<5);
  69     _delay_ms(1);
  70     bool charging = PINF&(1<<5) ? false : true;
  71
  72     // restore last register status
  73     DDRF  = (DDRF&~(1<<5))  | (ddrf_prev&(1<<5));
  74     PORTF = (PORTF&~(1<<5)) | (portf_prev&(1<<5));
  75
  76     // TODO: With MCP73831 this can not get stable status when charging.
  77     // LED is powered from PSEL line(USB or Lipo)
  78     // due to weak low output of STAT pin?
  79     // due to pull-up'd via resitor and LED?
  80     return charging;
  81 }
  82
  83 // Returns voltage in mV
  84 uint16_t battery_voltage(void)
  85 {
  86     // ADC disable voltate divider(PF4)
  87     DDRF  |=  (1<<4);
  88     PORTF |=  (1<<4);
  89
  90     volatile uint16_t bat;
  91     //ADCSRA |= (1<<ADEN);
  92
  93     // discard first result
  94     ADCSRA |= (1<<ADSC);
  95     while (ADCSRA & (1<<ADSC)) ;
  96     bat = ADC;
  97
  98     // discard second result
  99     ADCSRA |= (1<<ADSC);
 100     while (ADCSRA & (1<<ADSC)) ;
 101     bat = ADC;
 102
 103     ADCSRA |= (1<<ADSC);
 104     while (ADCSRA & (1<<ADSC)) ;
 105     bat = ADC;
 106
 107     //ADCSRA &= ~(1<<ADEN);
 108
 109     // ADC disable voltate divider(PF4)
 110     DDRF  |=  (1<<4);
 111     PORTF &= ~(1<<4);
 112
 113     return (bat - BATTERY_ADC_OFFSET) * BATTERY_ADC_RESOLUTION;
 114 }
 115
 116 static bool low_voltage(void) {
 117     static bool low = false;
 118     uint16_t v = battery_voltage();
 119     if (v < BATTERY_VOLTAGE_LOW_LIMIT) {
 120         low = true;
 121     } else if (v > BATTERY_VOLTAGE_LOW_RECOVERY) {
 122         low = false;
 123     }
 124     return low;
 125 }
 126
 127 battery_status_t battery_status(void)
 128 {
 129     if (USBSTA&(1<<VBUS)) {
 130         /* powered */
 131         return battery_charging() ? CHARGING : FULL_CHARGED;
 132     } else {
 133         /* not powered */
 134         return low_voltage() ? LOW_VOLTAGE : DISCHARGING;
 135     }
 136 }