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     // digital input buffer disable(24.9.5)
  24     DIDR0 = (1<<ADC0D) | (1<<ADC4D) | (1<<ADC7D);
  25     DIDR1 = (1<<AIN0D);
  26     DIDR2 = (1<<ADC8D) | (1<<ADC9D) | (1<<ADC11D) | (1<<ADC12D) | (1<<ADC13D);
  27
  28     // ADC disable voltate divider(PF4)
  29     DDRF  |=  (1<<4);
  30     PORTF &= ~(1<<4);
  31 }
  32
  33 // Indicator for battery
  34 void battery_led(battery_led_t val)
  35 {
  36     if (val == LED_TOGGLE) {
  37         // Toggle LED
  38         DDRF  |=  (1<<5);
  39         PINF  |=  (1<<5);
  40     } else if (val == LED_ON) {
  41         // On overriding charger status
  42         DDRF  |=  (1<<5);
  43         PORTF &= ~(1<<5);
  44     } else if (val == LED_OFF) {
  45         // Off overriding charger status
  46         DDRF  |=  (1<<5);
  47         PORTF |=  (1<<5);
  48     } else {
  49         // Display charger status
  50         DDRF  &= ~(1<<5);
  51         PORTF &= ~(1<<5);
  52     }
  53 }
  54
  55 bool battery_charging(void)
  56 {
  57     if (!(USBSTA&(1<<VBUS))) return false;
  58
  59     // Charger Status:
  60     //   MCP73831   MCP73832   LTC4054  Status
  61     //   Hi-Z       Hi-Z       Hi-Z     Shutdown/No Battery
  62     //   Low        Low        Low      Charging
  63     //   Hi         Hi-Z       Hi-Z     Charged
  64
  65     // preserve last register status
  66     uint8_t ddrf_prev  = DDRF;
  67     uint8_t portf_prev = PORTF;
  68
  69     // Input with pullup
  70     DDRF  &= ~(1<<5);
  71     PORTF |=  (1<<5);
  72     _delay_ms(1);
  73     bool charging = PINF&(1<<5) ? false : true;
  74
  75     // restore last register status
  76     DDRF  = (DDRF&~(1<<5))  | (ddrf_prev&(1<<5));
  77     PORTF = (PORTF&~(1<<5)) | (portf_prev&(1<<5));
  78
  79     // TODO: With MCP73831 this can not get stable status when charging.
  80     // LED is powered from PSEL line(USB or Lipo)
  81     // due to weak low output of STAT pin?
  82     // due to pull-up'd via resitor and LED?
  83     return charging;
  84 }
  85
  86 // Returns voltage in mV
  87 uint16_t battery_voltage(void)
  88 {
  89     // ADC disable voltate divider(PF4)
  90     DDRF  |=  (1<<4);
  91     PORTF |=  (1<<4);
  92
  93     volatile uint16_t bat;
  94     ADCSRA |= (1<<ADEN);
  95     _delay_ms(1);   // wait for charging S/H capacitance
  96
  97     ADCSRA |= (1<<ADSC);
  98     while (ADCSRA & (1<<ADSC)) ;
  99     bat = ADC;
 100
 101     ADCSRA &= ~(1<<ADEN);
 102
 103     // ADC disable voltate divider(PF4)
 104     DDRF  |=  (1<<4);
 105     PORTF &= ~(1<<4);
 106
 107     return (bat - BATTERY_ADC_OFFSET) * BATTERY_ADC_RESOLUTION;
 108 }
 109
 110 static bool low_voltage(void) {
 111     static bool low = false;
 112     uint16_t v = battery_voltage();
 113     if (v < BATTERY_VOLTAGE_LOW_LIMIT) {
 114         low = true;
 115     } else if (v > BATTERY_VOLTAGE_LOW_RECOVERY) {
 116         low = false;
 117     }
 118     return low;
 119 }
 120
 121 battery_status_t battery_status(void)
 122 {
 123     if (USBSTA&(1<<VBUS)) {
 124         /* powered */
 125         return battery_charging() ? CHARGING : FULL_CHARGED;
 126     } else {
 127         /* not powered */
 128         return low_voltage() ? LOW_VOLTAGE : DISCHARGING;
 129     }
 130 }