nRF52840 vs STM32WB55

nRF52840 vs STM32WB55: Nordic's BLE Ecosystem Leader vs ST's Dual-Core STM32 BLE SoC

The nRF52840 and STM32WB55 are both dual-protocol BLE + 802.15.4 SoCs, but they arrive from opposite ecosystem contexts. Nordic's nRF52840 dominates standalone BLE product development with the industry's largest BLE ecosystem. ST's STM32WB55 targets engineers already in the STM32 platform who need to add BLE or Zigbee to an existing STM32 design without re-platforming their entire development environment.

Overview

nRF52840 — 64 MHz Arm Cortex-M4F, 1 MB Flash, 256 KB RAM, BLE 5.0 + 802.15.4, USB 2.0. The dominant professional BLE SoC by deployment volume.

STM32WB55 (STMicroelectronics) — dual-core: 64 MHz Arm Cortex-M4 application core + 32 MHz Arm Cortex-M0+ RF core. 1 MB Flash (shared), 256 KB SRAM (partitioned between cores), BLE 5.0 + 802.15.4. The M0+ RF core runs ST's certified BLE and Zigbee firmware independently of the application M4 — architecturally mirroring TI's approach. Pin-compatible with STM32L4 series, enabling drop-in migration for teams with existing STM32L4 designs.

Key Differences

• Dual-core RF isolation: STM32WB55's dedicated M0+ RF core runs BLE and Zigbee stacks independently of the application M4, providing deterministic radio timing and eliminating SoftDevice interrupt conflicts — the same architectural benefit as TI's autonomous RF core.
• STM32 ecosystem compatibility: STM32WB55 is pin-compatible with STM32L4 and uses the same HAL, STM32CubeIDE, and STM32CubeMX as other STM32 products — critical for teams migrating existing STM32L4 designs to BLE without re-tooling.
• USB: Both have USB 2.0 FS — unusually, this is matched between the two chips.
• Flash allocation: STM32WB55 partitions Flash between M4 application and M0+ RF firmware. ST's BLE stack occupies approximately 120 KB; nRF52840's SoftDevice similarly reserves a region. Both total 1 MB.
• Peripheral set: STM32WB55 inherits the full STM32 peripheral library: advanced timers, DFSDM for digital PDM microphones, LCD driver, SAI audio interfaces, and hardware AES/PKA/RNG.
• Sleep current: Both achieve approximately 1.5 µA in deep sleep with an RTC running — effectively matched.
• Ecosystem breadth: Nordic's BLE-specific community is larger for standalone BLE products; the broader STM32 community is larger overall, treating BLE as one of many STM32 features.

Use Cases

When nRF52840 Excels

• Greenfield BLE-primary designs where Zephyr RTOS and nRF Connect SDK provide the most complete BLE development tools, profile libraries, and certification support.
• Thread/Zigbee + BLE concurrent sensor nodes with Nordic's well-tested multiprotocol scheduler.
• Multi-vendor module sourcing: Nordic's pre-certified module ecosystem includes dozens of vendors providing supply chain flexibility.
• BLE-forward product strategy where BLE is the product's primary interface and the STM32 ecosystem provides no legacy advantage.

When STM32WB55 Excels

• STM32 migration projects: teams with existing STM32L4 designs — established HAL code, peripheral drivers, and PCB layouts — reuse virtually all non-radio code when adding BLE.
• Mixed-signal products: STM32WB55's advanced analog peripherals (ADCs, DACs, op-amps) combined with BLE for industrial monitoring.
• TouchGFX UI + BLE: ST's TouchGFX framework combined with BLE enables LCD-equipped smart control panels on a familiar toolchain.
• STM32CubeAI inference: embedding neural network inference on the M4 while BLE runs independently on the M0+.

Verdict

The STM32WB55's strongest argument is STM32 ecosystem compatibility — it is the natural migration path for teams with existing STM32L4 designs adding BLE. For greenfield BLE-first products, the nRF52840's ecosystem depth, BLE qualification tooling, and larger module supplier network make it superior. Both chips support USB + BLE + 802.15.4 with dual-core RF isolation, making them similar on silicon but divergent on ecosystem. Choose based on your team's existing tools and legacy codebase. A practical evaluation tip: if your new design shares PCB real estate with another STM32 chip, or if your team has STM32CubeIDE workflows for analog sensing or TouchGFX UI already in production, the STM32WB55 is the lowest-friction path to adding BLE. In all other cases, the nRF52840 is the more productive starting point for a BLE-first design.