M5Stack Timer Power Unit with OLED Display (INA3221)

M5Stack Timer Power Unit for Scheduled Battery Systems

The M5Stack Timer Power Unit combines RTC-based power scheduling, battery charging, boosted 5V output, current and voltage monitoring, and a local OLED interface. An STM32G031G8U6 controller manages timing and system control, while the INA3221 monitors electrical conditions for the input and output paths.

This unit is designed around a connected 3.7V lithium-polymer battery. The USB Type-C port supplies 5V for battery charging and is not intended to directly power the Grove output. A built-in charging circuit is specified at 330mA, and the internal DC-DC boost stage provides 5V output for external devices through Grove. Output capability depends on the connected battery capacity and discharge rating.

Schedule Automatic Power-On and Power-Off

RTC cyclic timing control allows a device to power up only when work is required. This can reduce idle energy consumption in periodic sensor nodes, portable instruments, demonstration systems, or unattended devices. Define the wake schedule around actual startup time, measurement duration, data transmission, and safe shutdown behavior.

Monitor Voltage and Current with INA3221

The INA3221 provides real-time electrical monitoring for development and diagnostics. Use measured values to detect unexpected load changes, battery behavior, or output conditions, while remembering that system protection should still be designed around the battery, charger, wiring, and connected load.

Local OLED and Button Configuration

A 0.66-inch 64 × 48 OLED and two side buttons provide local status and configuration. Settings can also be accessed through I2C at address 0x56. Check the full I2C address map before adding the unit to a bus with other peripherals.

Battery and Output Planning

The Grove output current varies with battery capability. The product specification gives example output figures for different battery capacities and 1C discharge conditions; treat these as reference conditions rather than a universal guaranteed current for every battery. Size the battery for peak load, startup surge, runtime, temperature, and aging.

Technical setup details are available in the M5Stack TimerPWR documentation.