Custom firmware development for microcontrollers

Key differentiator

Firmware for safety-critical applications (IEC 61508 / SIL2)

Architecture ready for SIL2 certification, with experience preparing a platform for TÜV certification.

• Start-up and runtime self-tests: RAM test (March C-), CRC-32 flash integrity, CPU self-test, redundant ADC reads with plausibility checks
• Fail-safe design with a defined safe state, brown-out and tamper detection, reset-reason reporting
• Multi-layer watchdogs: hardware IWDG + task watchdog over RTOS tasks, stack-overflow detection, heartbeat monitoring
• MISRA C compliance via static analysis (clang-tidy)

What the Cyber Resilience Act requires from device manufacturers

The Cyber Resilience Act (CRA) makes these requirements mandatory for device manufacturers in the EU. I prepare firmware for them from the design stage:

• Signed firmware (ECDSA-P256 + SHA-256), signature verification in the bootloader, anti-rollback protection
• Custom bootloaders for STM32 (F1/F3/G0/L4 families) and ESP32 Secure Boot V2
• Flash protection (RDP, WRP, PCROP), security event log synchronized to the cloud
• Authentication of service commands (HMAC-SHA256 challenge-response)

What an OTA update with signed firmware looks like

A complete OTA chain: cloud → gateway → device → sub-modules over RS485, with integrity and signature verification at every step.

Technologies

MCU

STM32 across families (Cortex-M0+/M3/M4F, including low-power L4), ESP32 (ESP-IDF).

RTOS

FreeRTOS (CMSIS-RTOS v2) as well as bare-metal for small MCUs.

Languages

C (C11), C++ (tests), Python tooling, Dart/Flutter (mobile apps).

Industrial communication

Modbus RTU/TCP (master and slave), HART incl. 4-20 mA current loop, CAN with a custom application protocol, PROFIBUS DP, RS485, Ethernet.

Wireless and IoT

BLE (NimBLE, LE Secure Connections, QR provisioning), WiFi, HTTPS/TLS (mbedTLS), MQTT, LoRa, IQRF, NB-IoT/LTE-M.

Peripherals

SPI/I2C sensors, USB CDC, industrial displays, custom framed UART protocols with CRC and HMAC authentication.

Testing and continuous integration (CI)

• Hundreds of unit tests (GoogleTest) running on the host with a mocked HAL layer
• Coverage reports including branch coverage, CI pipeline (GitHub Actions) with a test dashboard
• Python integration tests and device simulators
• CMake cross-compilation, versioned releases with an FW tag for OTA

How I work

Layered modular architecture with HAL separation: shared modules (bootloader, security, protocols) are portable between boards of a product line on different MCUs. A new product in the line means a thin porting layer, not new development.

I use AI tools to accelerate routine work. The architecture and responsibility for the result stay with the engineer.

Who it is for

Manufacturers of industrial equipment, measurement and control instrumentation, gas detection, IoT devices with requirements for functional safety, cybersecurity and long-term maintenance.