When is Electron Powered By Battery

General
18

This version is much better. It uses the BAT_INT_PC13 interrupt to detect the rapid switching between fast charge and charge done when there is no battery. It’s much more efficient and doesn’t require being called from loop. You just initialize it once and use the getHasBattery() method to find out if there is one.

#include "Particle.h"

/**
 * Simple class to monitor for has power (USB or VIN), has a battery, and is charging
 *
 * Just instantiate one of these as a global variable and call setup() out of setup()
 * to initialize it. Then use the getHasPower(), getHasBattery() and getIsCharging()
 * methods as desired.
 */
class PowerCheck {
public:

	PowerCheck();
	virtual ~PowerCheck();

	/**
	 * You must call this out of setup() to initialize the interrupt handler!
	 */
	void setup();

	/**
	 * Returns true if the Electron has power, either a USB host (computer), USB charger, or VIN power.
	 *
	 * Not interrupt or timer safe; call only from the main loop as it uses I2C to query the PMIC.
	 */
	bool getHasPower();

	/**
	 * Returns true if the Electron has a battery.
	 */
	bool getHasBattery();

	/**
	 * Returns true if the Electron is currently charging (red light on)
	 *
	 * Not interrupt or timer safe; call only from the main loop as it uses I2C to query the PMIC.
	 */
	bool getIsCharging();

private:
	void interruptHandler();

	PMIC pmic;
	volatile bool hasBattery = true;
	volatile unsigned long lastChange = 0;
};

PowerCheck::PowerCheck() {
}

PowerCheck::~PowerCheck() {
}

void PowerCheck::setup() {
	// This can't be part of the constructor because it's initialized too early.
	// Call this from setup() instead.

	// BATT_INT_PC13
	attachInterrupt(LOW_BAT_UC, &PowerCheck::interruptHandler, this, FALLING);
}

bool PowerCheck::getHasPower() {
	// Bit 2 (mask 0x4) == PG_STAT. If non-zero, power is good
	// This means we're powered off USB or VIN, so we don't know for sure if there's a battery
	byte systemStatus = pmic.getSystemStatus();
	return ((systemStatus & 0x04) != 0);
}

/**
 * Returns true if the Electron has a battery.
 */
bool PowerCheck::getHasBattery() {
	if (millis() - lastChange < 100) {
		// When there is no battery, the charge status goes rapidly between fast charge and
		// charge done, about 30 times per second.

		// Normally this case means we have no battery, but return hasBattery instead to take
		// care of the case that the state changed because the battery just became charged
		// or the charger was plugged in or unplugged, etc.
		return hasBattery;
	}
	else {
		// It's been more than a 100 ms. since the charge status changed, assume that there is
		// a battery
		return true;
	}
}


/**
 * Returns true if the Electron is currently charging (red light on)
 */
bool PowerCheck::getIsCharging() {
	if (getHasBattery()) {
		byte systemStatus = pmic.getSystemStatus();

		// Bit 5 CHRG_STAT[1] R
		// Bit 4 CHRG_STAT[0] R
		// 00 – Not Charging, 01 – Pre-charge (<VBATLOWV), 10 – Fast Charging, 11 – Charge Termination Done
		byte chrgStat = (systemStatus >> 4) & 0x3;

		// Return true if battery is charging if in pre-charge or fast charge mode
		return (chrgStat == 1 || chrgStat == 2);
	}
	else {
		// Does not have a battery, can't be charging.
		// Don't just return the charge status because it's rapidly switching
		// between charging and done when there is no battery.
		return false;
	}
}

void PowerCheck::interruptHandler() {
	if (millis() - lastChange < 100) {
		// We very recently had a change; assume there is no battey and we're rapidly switching
		// between fast charge and charge done
		hasBattery = false;
	}
	else {
		// Note: It's quite possible that hasBattery will be false when there is a battery; the logic
		// in getHasBattery() takes this into account by checking lastChange as well.
		hasBattery = true;
	}
	lastChange = millis();
}



// Global variables
PowerCheck powerCheck;
unsigned long lastCheck = 0;
char lastStatus[256];

void setup() {
	Serial.begin(9600);
	powerCheck.setup();
}

void loop() {

	if (millis() - lastCheck > 2000) {
		lastCheck = millis();

		char buffer[256];
		snprintf(buffer, sizeof(buffer), "hasPower=%d hasBattery=%d isCharging=%d",
				powerCheck.getHasPower(), powerCheck.getHasBattery(), powerCheck.getIsCharging());

		if (strcmp(lastStatus, buffer) != 0) {
			strcpy(lastStatus, buffer);
			Particle.publish("battery", buffer, PRIVATE);
		}
	}
}
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