Table of Contents

AXP2101 - Enhanced Single Cell Li-Battery and Power System Management IC

Summary

The AXP2101 is an advanced power management IC (PMIC) manufactured by X-Powers, widely used in embedded devices such as the M5Stack CoreS3 (ESP32-S3-based). It provides comprehensive power management with multiple configurable voltage regulators, battery charging control, ADC measurements, fuel gauge, watchdog, and interrupt handling. It communicates over I2C at default address 0x34.

Documentation

Device Capabilities

Feature Details
DCDC Converters 5 channels (DCDC1-DCDC5) with configurable voltage outputs
LDO Regulators 4x ALDO (1-4), 2x BLDO (1-2), 1x CPUSLDO, 2x DLDO (1-2)
Battery Charging Linear charger with configurable current (0-1000 mA), voltage (4.0-4.44V), and termination settings
Fuel Gauge Built-in battery percentage calculation, gauge data ROM
ADC Battery voltage, VBUS voltage, system voltage, die temperature sensor, TS pin
Button Battery Backup/coin cell battery charging support
Interrupts 3 interrupt status registers supporting ~24 different IRQ sources
Watchdog Configurable timer with multiple reset behaviors
Power Control Power-on/off source detection, shutdown control, sleep/wakeup
Data Buffer 4-byte user data storage

Voltage Ranges

Channel Voltage Range Step
DCDC1 1500-3400 mV 100 mV
DCDC2 500-1200 mV / 1220-1540 mV 10 mV / 20 mV
DCDC3 500-1200 mV / 1220-1540 mV / 1600-3400 mV 10 mV / 20 mV / 100 mV
DCDC4 500-1200 mV / 1220-1840 mV 10 mV / 20 mV
DCDC5 1200 mV (special), 1400-3700 mV 100 mV
ALDO1-4 500-3500 mV 100 mV
BLDO1-2 500-3500 mV 100 mV
CPUSLDO 500-1400 mV 50 mV
DLDO1-2 500-3400 mV 100 mV

Usage

// Configure I2C pins for ESP32-S3 (M5Stack CoreS3)
Configuration.SetPinFunction(12, DeviceFunction.I2C1_DATA);
Configuration.SetPinFunction(11, DeviceFunction.I2C1_CLOCK);

I2cDevice i2cAxp2101 = new(new I2cConnectionSettings(1, Axp2101.I2cDefaultAddress));
Axp2101 power = new Axp2101(i2cAxp2101);

Important: make sure you read the documentation of your battery and set up the proper charging values and stop current. Overcharging your battery may damage it.

Setting up power rails

Configure DCDC and LDO voltage rails for your board. Example for M5Stack CoreS3:

// DCDC1: ESP32-S3 core — 3.3V (do NOT disable this!)
power.DcDc1Voltage = ElectricPotential.FromVolts(3.3);
power.EnableDcDc1();

// ALDO1: System peripherals — 1.8V
power.Aldo1Voltage = ElectricPotential.FromVolts(1.8);
power.EnableAldo1();

// ALDO2: Display/LCD — 3.3V
power.Aldo2Voltage = ElectricPotential.FromVolts(3.3);
power.EnableAldo2();

Warning: Never disable DCDC1 on a CoreS3 as it powers the ESP32-S3 core. Disabling it will brick the system until the next power cycle.

Battery charging

power.EnableCellBatteryCharge();
power.SetChargeConstantCurrent(ChargingCurrent.Current200mA);
power.SetChargeTargetVoltage(ChargeTargetVoltage.Voltage4V2);
power.SetPrechargeCurrent(PrechargeCurrent.Current25mA);
power.SetChargeTerminationCurrent(ChargeTerminationCurrent.Current25mA);
power.EnableChargeTerminationLimit();
power.SetThermalThreshold(ThermalThreshold.Temperature100C);

Battery status

int percentage = power.GetBatteryPercentage();
ElectricPotential batteryVoltage = power.GetBatteryVoltage();
ChargingStatus chargeStatus = power.GetChargerStatus();
bool batteryConnected = power.IsBatteryConnected;

Debug.WriteLine($"Battery: {percentage}%, {batteryVoltage.Volts:F2}V, {chargeStatus}");
Debug.WriteLine($"  Connected: {batteryConnected}");

VBUS monitoring

if (power.IsVbusGood)
{
    ElectricPotential vbusVoltage = power.GetVbusVoltage();
    Debug.WriteLine($"VBUS: {vbusVoltage.Volts:F2}V, Connected");
}

Using the power button

The power key supports short and long press detection via interrupts:

power.EnableIrq(Axp2101Irq.PowerKeyShortPress | Axp2101Irq.PowerKeyLongPress);
power.SetPowerKeyPressOnTime(0); // 128 ms
power.SetPowerKeyPressOffTime(0); // 4 s
power.EnableLongPressShutdown();
power.ClearIrqStatus();

// In your main loop:
if (power.IsPowerKeyShortPressIrq())
{
    Debug.WriteLine("Short press");
}

if (power.IsPowerKeyLongPressIrq())
{
    Debug.WriteLine("Long press");
}

power.ClearIrqStatus();

Temperature and ADC

Enable ADC channels and read measurements:

power.EnableBatteryVoltageMeasure();
power.EnableVbusVoltageMeasure();
power.EnableSystemVoltageMeasure();
power.EnableTemperatureMeasure();

Debug.WriteLine($"Die Temperature: {power.GetInternalTemperature().DegreesCelsius:F1} °C");
Debug.WriteLine($"System Voltage : {power.GetSystemVoltage().Volts:F2} V");

Watchdog

power.SetWatchdogConfig(WatchdogConfig.IrqAndReset);
power.SetWatchdogTimeout(WatchdogTimeout.Timeout8s);
power.EnableWatchdog();

// Feed the watchdog periodically:
power.ClearWatchdog();

Advanced features

The AXP2101 supports many additional features including VBUS input limits, backup battery charging, fast power-on sequencing, fuel gauge ROM programming, sleep/wakeup, and DCDC forced-PWM mode. You can check out the sample to get more details on how to use these features.

Note: this binding uses UnitsNet for units like Voltage and Temperature.

M5Stack CoreS3 Power Rail Mapping

Channel Usage Voltage
DCDC1 ESP32-S3 core 3.3V
ALDO1 System peripherals 1.8V
ALDO2 Display/LCD power 3.3V
ALDO3 Sensor/peripheral power 3.3V
ALDO4 Camera sensor 3.3V
BLDO1 I/O level shift 3.3V
BLDO2 Reserved/peripheral 3.3V

Differences from AXP192

If migrating from the Axp192 binding, note these key differences:

Feature AXP192 AXP2101
DCDC channels DCDC1, DCDC3 DCDC1-5
LDO channels LDO2, LDO3 ALDO1-4, BLDO1-2, CPUSLDO, DLDO1-2
Voltage ranges Simpler step logic Multi-range with variable steps (DCDC2-4)
ADC Full coulomb counter, multiple current ADC Simplified ADC (no coulomb counter)
Fuel gauge Coulomb counter based Built-in fuel gauge with battery % register
GPIO GPIO0-4 with configurable behavior No user-accessible GPIO (TS pin is configurable)
Interrupt registers 5 registers 3 registers (~24 IRQ sources)
Watchdog Not present Configurable watchdog timer
JEITA Not present Temperature-compensated charging
Data buffer 6 bytes 4 bytes
Chip ID register 0x03 (no standard value) 0x03 → 0x4A
Default I2C address 0x34 0x34 (same)
Edit this page