Low-Power IoT Firmware for BLE-Based Remote Battery Monitoring Using RAPIDSEA BSW/HAL and EEPROM Driver

Low-Power IoT Firmware for BLE-Based Remote Battery Monitoring Using RAPIDSEA BSW/HAL and EEPROM Driver

Snapshot

RAPIDSEA supported an energy technology OEM in building a production-ready remote battery monitoring system with BLE secure provisioning and low-power IoT firmware for industrial battery banks deployed in off-grid and semi-grid installations. By deploying the RAPIDSEA BSW/HAL Interface and EEPROM Driver modules, the team delivered a validated, power-optimised firmware stack covering BLE provisioning, I2C-based cell monitoring, EEPROM configuration persistence, and cloud telemetry, reaching SoP in 8 weeks while hitting a 10-year battery life target.

Customer Profile

Indian energy technology OEM supplying remote battery monitoring units for industrial UPS systems, solar storage banks, and telecom tower backup batteries. Devices deployed in locations with no reliable mains power and intermittent cellular connectivity, environments where firmware power efficiency and robust local data persistence are as critical as communication reliability.

Business Context

The replacement design used BLE for on-site provisioning and configuration by field technicians using a mobile app, and an NB-IoT modem for low-power cloud telemetry. The firmware architecture had to support three simultaneous demands: deterministic I2C polling of battery management ICs at configurable intervals, EEPROM-backed configuration persistence surviving power loss events, and aggressive MCU duty cycling to hit the 10-year battery life target.

Key Challenges

•  Ultra-Low Power Duty Cycling: The target MCU had to spend the majority of its operating life in deep sleep, waking only for scheduled I2C polling cycles, BLE advertisement windows, and NB-IoT uplink sessions. Any peripheral driver holding a clock domain active outside its assigned wake window directly eroded the battery life target.
•  BLE Secure Provisioning: Field technicians provisioning the device via the mobile app needed to write configuration parameters securely over BLE. Unauthenticated BLE write access to configuration registers was flagged as a security requirement by the customer's enterprise clients.
•  EEPROM Configuration Persistence: Configuration parameters written over BLE had to survive indefinite power loss events. The EEPROM write cycle had to be atomic and verified, with corruption detection on readback at every boot.
•  I2C Battery Monitor IC Integration: I2C transaction errors, such as clock stretching timeouts, NACK responses during cell balancing activity, had to be handled gracefully without hanging the polling loop or corrupting the data stream.
•  BLE Stack and Application Coexistence: Running BLE advertisement and connection handling concurrently with I2C polling and NB-IoT uplink sessions required careful task prioritisation. Previous firmware versions exhibited I2C transaction failures during active BLE connection events due to interrupt priority conflicts.

Target Platform

Nordic nRF52840 SoC, a Bluetooth 5.0 capable, Cortex-M4 based MCU with hardware AES acceleration and a power management unit supporting multiple low-power operating modes. RAPIDSEA BSW/HAL Interface modules ported to the nRF52840 HAL, providing a clean abstraction above the Nordic SDK peripheral layer.

Why RAPIDSEA

•  Power-Aware HAL Architecture: RAPIDSEA BSW/HAL modules expose explicit peripheral enable and disable callbacks at the HAL boundary, allowing the application's power manager to gate individual peripheral clock domains independently between wake cycles.
•  Production-Grade EEPROM Driver: RAPIDSEA EEPROM Driver implements atomic write-verify sequences with configurable retry counts and CRC-based corruption detection. At every boot, the driver validates the stored configuration block against its CRC before applying it, falling back to factory defaults on corruption detection.
•  I2C Error Recovery: RAPIDSEA I2C HAL module implements bus recovery sequences — SCL toggling to release a stuck SDA line — triggered automatically on timeout or NACK detection. This eliminated the I2C hang condition experienced during battery balancing activity.

Solution: How to Build a BLE Secure Provisioning IoT Device with Low-Power Firmware

RAPIDSEA HAL Porting on nRF52840: I2C, GPIO, and Timer

I2C master instance mapped to the nRF52840's TWIM peripheral in non-blocking DMA mode, allowing I2C transactions to complete without CPU involvement. GPIO interrupt callbacks configured for the battery management IC's alert line. HAL bring-up across all peripheral instances completed in two days.

EEPROM-Backed Configuration Persistence

RAPIDSEA EEPROM Driver configured for a Microchip 24LC256 I2C EEPROM. Each BLE-initiated configuration write triggered an atomic EEPROM update sequence: write, read-back verify, CRC recalculation, CRC block write. Zero configuration loss across 200 simulated power interruption cycles in endurance testing.

BLE Secure Provisioning Integration

GATT characteristics for each configuration parameter protected with BLE pairing requirements, enforcing encrypted, authenticated connections before any write operations. BLE advertisement activated only during provisioning sessions triggered by physical button press, keeping the radio silent during normal monitoring operation.

Low-Power Duty Cycle Architecture

RAPIDSEA Timer module's low-power wakeup interface used to schedule I2C polling cycles, defaulting to 60-second cycles in normal operation and 5-second cycles during active alert conditions. All HAL peripheral instances explicitly disabled via power callbacks between wake cycles. Average current consumption: 4.2 µA - within the 10-year battery life budget.

Cloud Telemetry Over NB-IoT

Accumulated cell voltage and temperature samples batched into JSON payloads using RAPIDSEA File Formats module and transmitted over NB-IoT using RAPIDSEA IoT stack's MQTT interface. Out-of-threshold alert events triggered immediate uplink, sub-minute fault notification latency without increasing baseline power consumption.

Engineering Impact

Conclusion

Building low-power IoT firmware that simultaneously manages BLE secure provisioning, deterministic I2C battery monitoring, EEPROM configuration persistence, and NB-IoT cloud telemetry on a duty-cycled MCU demands precise control of every peripheral's power domain. The RAPIDSEA BSW/HAL and EEPROM Driver modules gave this energy OEM a production-validated peripheral foundation that delivered the 10-year battery life target without sacrificing provisioning security or telemetry reliability.

Looking to build a secure, low-power remote monitoring solution?Connect with our experts to explore RAPIDSEA-based implementations.