Four circuits to start from.

More than symbols: four editable carrier boards.

Each folder includes a KiCad project, schematic and PCB, together with the required library tables. Local libraries provide the ELPM-S3LW v1.6 symbol, module footprint and STEP model; the fourth project also includes the LIS2DW12TR symbol, LGA-12 footprint and 3D model. Each example is therefore self-contained and easier to copy, compare or turn into a custom board.

The power latch separates the event from the work.

In conventional deep sleep the microcontroller remains powered and decides when to wake. With the hardware latch, the main rails can instead be physically disconnected. An external source asserts MASTER or produces the required transition on WAKE; the latch enables the switched domain, ELPM-S3LW performs a full boot and firmware keeps power on for as long as needed.

The carrier board must therefore separate three functions: VBAT supplies anything that must detect an event while the system is off; VRTC retains time and alarms when scheduled wake-up is required; P_DRAIN supplies loads that should exist only during the active cycle. The VMCU rail is configured according to the strategy selected in the design.

The four projects add complexity one step at a time.

01 / Direct 3.3 V supply

The first project bypasses the power latch and keeps the module continuously powered. It is the simplest starting point for programming, debugging, interface verification and firmware development. Optional 0 Ω links make it possible to isolate domains or create variants without redesigning the board; unused sections can be marked DNP.

02 / Battery power latch

The second project introduces the battery, VBAT rail and switched P_DRAIN output. It shows how to choose which domains connect directly to the battery and which are powered only while the latch is active. MASTER is the primary input for sensors, dry contacts, reed switches or Hall sensors; WAKE can add a second source using the specified transition.

03 / RTC periodic wake-up

The third project keeps the power latch and supplies VRTC from the battery, allowing the RTC to retain time and generate an alarm while the rest of the system is off. It is a foundation for data loggers, meters and sensors that sample or transmit on a schedule. After every boot, firmware must clear the alarm cause, schedule the next event and only then release the latch.

04 / Accelerometer sensor node

The fourth project applies the architecture to a LIS2DW12TR connected over I²C and exposing an INT line. The accelerometer remains in the domain required to detect motion; when the configured condition occurs, its interrupt triggers the latch wake path. ELPM-S3LW boots, reads the sensor, processes the event and can transmit it over LoRa, Wi-Fi or BLE before switching the main domain off again.

From motion to controlled shutdown.

1. The LIS2DW12TR monitors motion in its low-power operating mode.
2. The sensor's internal logic detects the configured condition and asserts INT.
3. The interrupt reaches the wake input and activates the power latch.
4. VMCU and the switched domains become available; the ESP32-S3 boots.
5. Firmware immediately reads LIS2DW12TR status to identify and clear the interrupt source.
6. After measurement, logging and communication, firmware releases the latch and the node returns to its minimum-power state.

Before committing the final prototype, verify interrupt polarity and latched/pulsed behaviour, minimum battery voltage, I²C pull-ups, reverse current between domains and signal duration during boot. Motion threshold, duration and filtering must also be configured in the LIS2DW12TR for the real mechanical installation.

Use them as a starting point, not a substitute for verification.

• Open the project closest to your architecture and keep its local libraries with it.
• Explicitly decide which loads belong on VBAT and which on P_DRAIN.
• Calculate always-on consumption including sensor, RTC, pull-ups and leakage.
• Check pins, electrical limits and recommendations against the current ELPM-S3LW and LIS2DW12TR datasheets.
• Test short events, persistent interrupts, low battery, reset during boot and communication failures.

The package is intended to accelerate development: schematic and layout remain editable, so power, connectors, antenna, sensors and mechanics can be adapted to the final product.