Bluetooth Low Energy MCU provides integrated solution for smart connected devices


RSL15 from onsemi protects connected devices with a comprehensive set of advanced security functions including TrustZone® support and root-of-trust

The RSL15 from onsemi, a secure low-power wireless microcontroller which implements Bluetooth® Low Energy 5.2 networking, provides a complete set of control and connectivity functions for smart devices in industrial and medical applications.


Based on an Arm® Cortex®-M33 processor core, the RSL15 features built-in power management, a wide supply-voltage range suitable for coin cells, a flexible set of GPIOs, and an extensive set of peripherals. The RSL15 includes 80 kbytes of RAM. The MCU supplied in a WLCSP package has 512 kbytes of Flash memory, while the QFN-packaged MCU has either 284 kbytes or 512 kbytes


The RSL15 is backed by a comprehensive but easy-to-use software development kit (SDK) which includes a cybersecurity platform. It also provides various sample applications which demonstrate key features such as:

  • Low-power Smart Sense mode for acquiring sensor data
  • Tools for configuring power-management functions
  • Bluetooth Low Energy functions
  • Ultra low-power sleep modes


onsemi has ensured that connected devices based on the RSL15 are protected against cyber-attack. The RSL15 provides a comprehensive mix of security capabilities, including Arm TrustZone® technology, which provides trusted execution environments for at-risk peripherals and functions. The RSL15 also features Arm CryptoCell™-312 technology to provide root-of-trust and additional security mechanisms such as:

  • True random number generator
  • Standard encryption accelerators
  • Support for a wide range of encryption functions, including:
    • AES 128/192/256
    • SHA
    • Public key infrastructure
    • Elliptic curve cryptography
    • Message authentication
  • Secure boot embedded in hardware ROM
    • Hardware-based root-of-trust using secrets stored in dedicated hardware
    • Managed life-cycle model
  • Secure key storage
  • Secure debug controlled with certificates


The RSL15 supports capabilities provided by the Bluetooth 5.2 specification, including extended advertising, long range, a data-transmission rate of up to 2 Mbits/s, up to 10 simultaneous connections, and localization through detection of the angle of arrival and angle of departure of wireless transmissions.


The low power consumption of the RSL15 has been verified by the Embedded Microprocessor Benchmark Consortium. The MCU achieved a score of 60.5 on its ULPMark™-CoreMark benchmark in the performance category, the best in its class. On the ULPMark-CoreProfile benchmark, which calculates the deep-sleep efficiency of MCUs, the RSL15 holds second place, only behind the onsemi RSL10 wireless MCU.


  • Bluetooth Low Energy 5.2 certified:
    • Backwards compatibility with earlier Bluetooth specifications
  • 36 nA sleep mode current
  • 7 mA peak Receive current at 1 Mbit/s
  • 3 mA peak Transmit current at 0 dBm output power
  • -94 dBm sensitivity at 2 Mbits/s data rate
  • Configurable output-power range: -17 dBm to +6 dBm
  • Supply-voltage range: 1.2 V to 3.6 V


  • Industrial automation and sensing
  • Connected medical sensors
  • Wearable devices
  • Asset tracking
  • Electronic tags
  • Access control
  • Electronic labels
  • Data loggers
  • Smart appliances
  • Energy-harvesting switches

Evaluation Board

Board Part Number: RSL15-EVB

The RSL15 QFN evaluation and development board enables developers to evaluate the performance and capabilities of the RSL15 Bluetooth® microcontroller, and to develop, demonstrate, and debug applications.

Key features of the board include:

  • Easy code download and debugging with SEGGER J−Link on−board technology
  • JTAG debug port accessible via a 10-pin header
  • Automatic power supply switching between battery and USB
  • Access to all RSL15 interfaces and GPIOs via standard 0.1” headers
  • Two push-button switches
    • One dedicated to resetting the device via the NRESET pin
    • One connected to GPIO0
  • Test points and ground hooks for easy probing
  • CR2032 battery holder
  • Simple configuration for power measurements
  • Integrated PCB antenna with matching and filtering network
  • UFL connector for conducted RF connections

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onsemi — RSL15 Secure Wireless Microcontroller

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