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     // Charger Status:
  53     //   MCP73831   MCP73832   LTC4054  Status
  54     //   Hi-Z       Hi-Z       Hi-Z     Shutdown/No Battery
  55     //   Low        Low        Low      Charging
  56     //   Hi         Hi-Z       Hi-Z     Charged
  57
  58     // preserve last register status
  59     uint8_t ddrf_prev  = DDRF;
  60     uint8_t portf_prev = PORTF;
  61
  62     // Input with pullup
  63     DDRF  &= ~(1<<5);
  64     PORTF |=  (1<<5);
  65     _delay_ms(1);
  66     bool charging = PINF&(1<<5) ? false : true;
  67
  68     // restore last register status
  69     DDRF  = (DDRF&~(1<<5))  | (ddrf_prev&(1<<5));
  70     PORTF = (PORTF&~(1<<5)) | (portf_prev&(1<<5));
  71
  72     // TODO: With MCP73831 this can not get stable status when charging.
  73     // LED is powered from PSEL line(USB or Lipo)
  74     // due to weak low output of STAT pin?
  75     // due to pull-up'd via resitor and LED?
  76     return charging;
  77 }
  78
  79 // Returns voltage in mV
  80 uint16_t battery_voltage(void)
  81 {
  82     volatile uint16_t bat;
  83     //ADCSRA |= (1<<ADEN);
  84
  85     // discard first result
  86     ADCSRA |= (1<<ADSC);
  87     while (ADCSRA & (1<<ADSC)) ;
  88     bat = ADC;
  89
  90     // discard second result
  91     ADCSRA |= (1<<ADSC);
  92     while (ADCSRA & (1<<ADSC)) ;
  93     bat = ADC;
  94
  95     ADCSRA |= (1<<ADSC);
  96     while (ADCSRA & (1<<ADSC)) ;
  97     bat = ADC;
  98
  99     //ADCSRA &= ~(1<<ADEN);
 100
 101     return (bat - BATTERY_ADC_OFFSET) * BATTERY_ADC_RESOLUTION;
 102 }
 103
 104 static bool low_voltage(void) {
 105     static bool low = false;
 106     uint16_t v = battery_voltage();
 107     if (v < BATTERY_VOLTAGE_LOW_LIMIT) {
 108         low = true;
 109     } else if (v > BATTERY_VOLTAGE_LOW_RECOVERY) {
 110         low = false;
 111     }
 112     return low;
 113 }
 114
 115 battery_status_t battery_status(void)
 116 {
 117     if (USBSTA&(1<<VBUS)) {
 118         /* powered */
 119         return battery_charging() ? CHARGING : FULL_CHARGED;
 120     } else {
 121         /* not powered */
 122         return low_voltage() ? LOW_VOLTAGE : DISCHARGING;
 123     }
 124 }