Particle Low Power Operation / Charging

The 3V3 pin will have 0.460 V when in standby mode with LiPo power (only) and EN pin grounded.  

Background

Battery power capability is measured in C's.   A C is the Amp-hour capacity divided by 1 hour (C = 2 Ah / 1 = 2A).   DC power is defined in terms of watts, or the power that is delivered to sustain a voltage at a specified current.   W-h (Watt-hours) is the measure of voltage * Amp-hours.   A 300 mAh battery sustaining 3.6 V (nominal) will deliver 1080 mWh.  

 

Charging Status

#include "Particle.h"

#if (PLATFORM_ID == PLATFORM_XENON)
SYSTEM_MODE(MANUAL);
#endif

/////////////////////////////////////////////////////////////////////////
// Battery charging status 

// Source: https://github.com/rickkas7/DiagnosticsHelperRK
#include "DiagnosticsHelperRK.h"

const unsigned long TIMER_INTERVAL_MS = 1000;
unsigned long timerLast = 0;
int lastPowerSource  = -1;
int powerSource = -1;

#if PLATFORM_ID == PLATFORM_BORON
    #define PWR -1 // Fake assignment to avoid error
#endif
/////////////////////////////////////////////////////////////////////////


void setup() {
  pinMode(D7, OUTPUT);
  
  Serial.begin(9600);
  waitFor(Serial.isConnected, 30000);
  delay(1000);
  Serial.printlnf("System version: %s", System.version().c_str());
  Serial.printlnf("Free RAM %d", System.freeMemory());

} // setup()


void loop() {

  if (timerLast > millis())  timerLast = millis();
  if ((millis() - timerLast) > TIMER_INTERVAL_MS) {
    if (PLATFORM_ID == PLATFORM_ARGON || PLATFORM_ID == PLATFORM_XENON) {       
        pinMode(PWR, INPUT);
        byte pwr = digitalRead(PWR);    // PWR: 0=no USB power, 1=USB powered
        // NOTE:  Need to test with VIN power
        if (pwr == 0)
          powerSource = 5;  // POWER_SOURCE_BATTERY                 
        else
          powerSource = 2;  // POWER_SOURCE_USB_HOST
    } else if (PLATFORM_ID == PLATFORM_BORON) {
      // DiagnosticsHelper works on Boron LTE (the Argon and Xenon don’t have a PMIC chip)
      powerSource = DiagnosticsHelper::getValue(DIAG_ID_SYSTEM_POWER_SOURCE);
    }    
    if (powerSource != lastPowerSource) {
        lastPowerSource = powerSource;
        // POWER_SOURCE_UNKNOWN = 0,
        // POWER_SOURCE_VIN = 1,
        // POWER_SOURCE_USB_HOST = 2,
        // POWER_SOURCE_USB_ADAPTER = 3,
        // POWER_SOURCE_USB_OTG = 4,
        // POWER_SOURCE_BATTERY = 5
        if (powerSource == 1 || powerSource == 2 || powerSource == 3 || powerSource == 4) {
          Particle.publish("PWR", String::format("USB %d", powerSource), PRIVATE);
        } else if (powerSource == 5) {
          Particle.publish("PWR", String::format("battery %d", powerSource), PRIVATE);
        } else
          Particle.publish("PWR", String::format("%d", powerSource), PRIVATE); 
    }
    timerLast = millis();
  } // timer

} // loop()

 

Low Power Operation

Boron battery life/use estimates by Rftop

 

Sleep Modes

As of version 1.5.0 a new API System.sleep() exists to assist with low power operation.   The two sleep modes are STOP and HIBERNATE.  

• STOP
- The RTC keeps running, and cellular network is kept running.   All devices can also wake from a time interval (up to 24 days).   For Gen 3 devices, BLE is kept on if it is designated as the wake-up source.   GPIO, UART, and ADC are all kept active and remain constant.   The SystemSleepConfiguration::network() option for the Boron keeps the cellular modem connected to the cellular network for fast reconnection (works best for 23 minute sleep periods).  
• HIBERNATE - Gen 3 devices can only wake from any GPIO pin on RISING, FALLING, or CHANGE.   BLE and the RTC are off.  

The command System.sleep() can be configured to monitor a digital output and cause a device to wake up from sleep mode.  

 

Other External Sleep / Wake-Up Options

AF TPL5110 Low Power Breakout (trigger EN pin)

AF TPL5111 Low Power Reset Timer (break power input)

 

Solar Charging

Adafruit USB, DC, & Solar LiPoly Charger

A very small 6V 1W solar charger has a size of 3.5" x 4.4" x 0.2" (89mm x 113mm x 5mm).  

 

Links

Connection to USB pin rather than USB connector

errors in analogRead(BATT) are significantly reduced at a Li-Po voltage of 3.9V or above

Adafruit INA219 Featherwing

Adafruit USB, DC, & Solar LiPoly Charger

Low-Poser Boron LTE using EN pin (great data)

 

More AF FeatherWing products from Adafruit and from Particle

 

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