147 lines
3.2 KiB
C
147 lines
3.2 KiB
C
#include "power.h"
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#include <stdint.h>
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#include <avr/io.h>
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#include <util/delay.h>
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#include <ssd1306xled.h>
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#define VccOffTreshold 3000
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#define VccOnTreshold 3100
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#define SSD1306CommandOff 0xAE
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#define SSD1306CommandOn 0xAF
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PowerState powerState = BatteryLow;
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uint16_t vcc = 0;
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uint8_t screenInvalidated = 0;
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// Forward declarations
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uint16_t readVCC();
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void checkPower()
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{
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vcc = readVCC();
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switch (powerState)
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{
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case On:
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// Turn display off below 3v. It holds up surprisingly well, but at around
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// 1.5v it does corrupt the screen and requires reinitialization when the
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// voltage is turned back up.
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//
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// ...although by then the battery would be damaged, but still, turning off at
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// 3v means we're still in the safe range when we go into battery saving mode
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// and the reinitialization afterwards prevents any issues.
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if (vcc < VccOffTreshold)
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{
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setPowerState(BatteryLow);
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// TODO go into a sleep cycle until the battery is recharged
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_delay_ms(10);
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}
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break;
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case BatteryLow:
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if (vcc > VccOnTreshold)
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setPowerState(On);
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else
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{
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// TODO continue sleep cycle
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_delay_ms(10);
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}
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break;
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case ManualOff:
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// TODO go into sleep mode
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_delay_ms(10);
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break;
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}
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}
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void setPowerState(PowerState newState)
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{
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if (newState == powerState) return;
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switch (newState)
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{
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case On:
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ssd1306_send_command(SSD1306CommandOn);
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break;
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case BatteryLow:
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case ManualOff:
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if (powerState == On)
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ssd1306_send_command(SSD1306CommandOff);
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break;
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}
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powerState = newState;
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}
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uint8_t getScreenInvalidated()
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{
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if (screenInvalidated)
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{
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screenInvalidated = 0;
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return 1;
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}
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return 0;
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}
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void setScreenInvalidated()
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{
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screenInvalidated = 1;
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}
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// Source: http://21stdigitalhome.blogspot.nl/2014/10/trinket-attiny85-internal-temperature.html
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//
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// I've tried many versions and none seemed to work with my ATTiny85-20SU's.
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// For example:
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// https://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/
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// https://github.com/cano64/ArduinoSystemStatus/blob/master/SystemStatus.cpp
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// http://www.avrfreaks.net/forum/attiny-adc-using-internal-ref-measure-vcc-problem
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//
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// The key for me was in: ADMUX = 0x0c | _BV(REFS2);
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uint16_t readVCC() {
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ADCSRA |= _BV(ADEN);
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// Read 1.1V reference against AVcc
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// set the reference to Vcc and the measurement to the internal 1.1V reference
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/*
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#if defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
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ADMUX = _BV(REFS0) | _BV(MUX4) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
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#elif defined (__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
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ADMUX = _BV(MUX5) | _BV(MUX0);
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#elif defined (__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
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ADMUX = _BV(MUX3) | _BV(MUX2);
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#else
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ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
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#endif
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*/
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ADMUX = 0x0c | _BV(REFS2);
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_delay_ms(100);
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ADCSRA |= _BV(ADSC);
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while (bit_is_set(ADCSRA,ADSC));
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uint16_t result = ADC;
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ADCSRA &= ~(_BV(ADEN));
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return result == 0 ? 0 : 1125300L / result; // Calculate Vcc (in mV); 1125300 = 1.1*1023*1000
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} |