A survey of Bluetooth connectivity modules for IoT applications: part 4

This final part of the FAQ covers the Bluetooth connectivity modules from Nordic Semiconductor and STMicroelectronics. The modules covered are based on higher processing power and advanced versions of ARM Cortex processors.

Nordic Semiconductor: nRF54L Series

The nRF54L series (Figure 1) from Nordic Semiconductor features a 128 MHz Arm Cortex-M33, providing sufficient processing power for the efficient execution of complex algorithms and real-time processing. The modules include TrustZone technology for advanced security, built-in DSP capabilities, a memory protection unit, an integrated floating-point unit for precise calculations, and support for external accelerators and debugging options.

bluetooth — Figure 1. The three variants of the nRF54L series Bluetooth modules from Nordic Semiconductor. (Image: Nordic Semiconductor)

The module’s scalable memory configurations offer up to 1.5 MB of non-volatile memory (NVM) and 256 KB of RAM. NVM technologies offer lower power consumption, comparable or superior performance, and minimize latency by optimizing data locality and access patterns. NVM with RAM as a high-speed cache reduces the time to access frequently used data.

Based on the combination of NVM and RAM, the nRF54L Series includes three System-on-Chip (SoC) variants:

nRF54L15 (with 1524 KB NVM, 256 KB RAM)
nRF54L10 (with 1022 KB NVM, 192 KB RAM)
nRF54L05 (with 500 KB NVM, 96 KB RAM)

All the SoCs support Bluetooth 6.0, introducing features like Decision-Based Advertising Filtering (DBAF), which optimizes power usage in Bluetooth Low Energy (BLE) devices. With the SoCs supporting 2 Mbps/1 Mbps/500 Kbps/125 Kbps, the applications extend from high-speed communications such as data streaming to low-power, long-range applications such as agricultural monitoring systems.

Utilizing multiple protocols like Thread, Matter, and Zigbee enables a wide range of applications, from home automation to industrial monitoring with higher throughput. The proprietary 2.4 GHz mode benefits applications requiring high throughput, such as streaming audio or video content and efficiently transferring large files.

The design complexity is greatly reduced by incorporating multiple peripherals (including the new Global RTC available in System OFF, 14-bit ADC, and high-speed serial interfaces) and a coprocessor (128 MHz RISC-V) on a single chip. This feature has several advantages, including eliminating the need for multiple external integrated circuits, cost efficiency, compact form factor, and power efficiency.

The -104 dBm sensitivity at 125 Kbps allows devices to maintain connections over longer distances and detect signals in challenging environments. IEEE 802.15.4 sensitivity of -102 dBm supports reliable communication for protocols like Thread and Zigbee, which is important for IoT applications.

With a configurable output power of up to +8 dBm, developers can optimize their designs based on range requirements while managing power consumption effectively.

In addition to active mode efficiency, the System ON IDLE state can achieve current consumption as low as 2.0 µA for 96 KB of RAM. The System OFF mode can drop to 0.6 µA, which can conserve energy. This ultra-low power consumption prolongs not only battery life but also the life of more compact devices.

The devices are available in compact packages, including a QFN48 (6.0 x 6.0 mm) option with 31 GPIO pins and a WLCSP (2.4 x 2.2 mm) variant with 32 GPIO pins, enabling integration into space-constrained applications.

Figure 2. The nRF54L15 DK development kit for the three SoC variants of the nRF54L series. (Image: Nordic Semiconductor)

Nordic Semiconductor has made it easy to prototype the nRF54L series with the help of the nRF54L15 DK development, as shown in Figure 2. Even though the kit has only the nRF54L15 SoC, the other two SoCs can be emulated. The programmable LEDs and buttons make custom input/output operations convenient. The kit has provisions for connecting an NFC antenna and external memory.

STMicroelectronics: STM32WB55XX

The STM32WB55XX MCUs from STMicroelectronics feature an Arm 32-bit Cortex-M4 CPU that operates at frequencies up to 64 MHz. The Arm processor delivers performance metrics of 80 DMIPS (Dhrystone MIPS), which has efficient processing capabilities for demanding applications. It includes built-in DSP instructions and FPU (floating point unit), enabling efficient handling of complex mathematical computations essential for audio processing, motor control, and other signal processing tasks. It has a performance benchmark of 1.25 DMIPS/MHz and a CoreMark score of 219.48.

Figure 3 shows a chart describing the various products of STM32WB55XX according to their RAM size and pin count. The STM32WB55CG has 1 MB of flash memory with sector protection (PCROP) and up to 256 KB of SRAM, including 64 KB with hardware parity check. This combination allows for efficient data processing, and the system can store larger applications and more complex data sets.

The sector protection (PCROP) feature enhances security by protecting specific flash memory sectors and safeguards important data from unauthorized access or accidental overwriting. Including 64 KB with hardware parity check enhances data integrity by detecting memory errors.

The MCUs have the advantages of a 2.4 GHz RF transceiver, supporting Bluetooth 5.4, IEEE 802.15.4-2011 PHY, and MAC, as well as protocols like Thread 1.3 and Zigbee 3.0. Multiprotocol support allows various applications, including smart home devices, industrial automation, and health monitoring systems. Bluetooth 5.4 enables low power consumption, higher data rates, increased range for audio streaming, and real-time sensor data transmission.

A lower RX sensitivity level of -96 dBm for BLE at 1 Mbps and -100 dBm for IEEE 802.15.4 means that the MCUs can detect weaker signals and maintain connections over longer distances. An extremely low power consumption level of 13 nA shutdown mode is ideal for minimal battery drain, significantly extending the life of battery-powered devices.

Programmable output power up to +6 dBm in 1 dB steps enables designers to optimize power consumption based on requirements. For example, lower output power can be used when devices are close together, conserving energy while maintaining communication.

Operating at just 4.5 mA in Rx mode and 5.2 mA in Tx mode allows for efficient energy usage, enabling devices to maintain connectivity without excessive power drain, which is especially beneficial for battery-powered applications.

The integration of robust security measures such as secure firmware installation, hardware encryption (AES), public key authority (PKA), and a true random number generator (RNG) offers significant advantages in protecting sensitive data.

Figure 4. The STM32 Nucleo-64 development board with STM32WB55RG MCU. (Image: STMicroelectronics)

The STM32 Nucleo-64 development board, as shown in Figure 4, is based on the STM32WB55RG MCU, which can quickly test and develop new ideas across various IoT applications. The boards support Arduino Uno Revision 3 connectivity and include ST Morpho headers. The STM32Cube software package provides comprehensive libraries and examples, compatible with various IDEs such as IAR, Keil, GCC-based IDEs, and Mbed

Summary

The nRF54L series has a high processing power of 128 MHz, and STM32WB55XX focuses on ultra-low power consumption. The nRF54L series has options for different data rates combined with the BLE 6. The STM32WB55XX has a variety of products based on the pin count, which is useful for custom product design. Both modules support multithreading and are also well-supported with dedicated development kits.