A survey of Bluetooth connectivity modules for IoT applications: part 1

Bluetooth connectivity continues to gain traction for IoT applications because of its unique features, such as Bluetooth Low Energy (BLE), effectiveness in short-range communications, and lower cost deployment. This multipart FAQ series will cover several manufacturers, including Silicon Labs and Infineon Technologies, characterized by ARM Cortex processors.

Silicon Labs: EFR32BG26 Series 2 Bluetooth SoC

The EFR32BG26 Series 2 Bluetooth SoC from Silicon Labs, shown in Figure 1, has an ARM Cortex-M33 core running at 78 MHz. Its 3200 kB Flash and 512 kB RAM memory allows storing multiple firmware versions, support complex data structures, enable efficient multitasking, and secure over-the-air (OTA) software updates.

Figure 1. The EFR32BG26 Series 2 Bluetooth SoC from Silicon Labs. (Image: Silicon Labs)

The module supports BLE, which operates in the 2.4 GHz ISM band and offers a maximum data rate of 1 Mbit/s. It is an energy-efficient approach to maintaining connectivity while reducing power consumption. It supports a variety of network topologies, including point-to-point, broadcast, and mesh networks, enabling large-scale device networks.

The inclusion of AI/ML hardware acceleration and a Matrix-Vector Processor significantly reduces computational time while consuming less power. This suits edge computing applications, particularly those that require local sensor data processing.

Receiver sensitivity measures the minimum signal strength a receiver can detect and successfully process. Their lower sensitivity, down to -105.9 dBm at 125 kbps, allows the reception of weaker signals, enabling reliable communication even in challenging RF environments.

TX power, the strength of the signal transmitted by the module, is high, up to 19.5 dBm, ensuring good range. This combination is particularly valuable in smart building applications where signals must penetrate walls and floors.

Its deep sleep current of just 1.4 µA enables long battery life. A relatively low RX current of 5.4 mA during active operation helps maintain efficient energy usage during data reception.

The module is protected by the company’s proprietary Secure Vault technology. Hardware cryptographic acceleration and the True Random Number Generator keep private data and conversations safe. The addition of ARM TrustZone provides an extra layer of security by creating isolated secure and non-secure execution environments within a single processor.

Figure 2 shows the module’s various features as a block diagram. To visualize and interlink them, the features have been categorized into EM0 (Run), EM1 (Sleep), EM2 (Deep Sleep), EM3 (Stop), and EM4 (Shutoff).

Figure 2. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia (Image: Silicon Labs)

The wide temperature range of -40 °C to 125 °C makes it suitable for indoor and outdoor IoT applications. With these features, the EFR32BG26 is a good choice for IoT applications like smart home devices, lighting, building automation systems, and industrial IoT sensors and controls.

Infineon Technologies: CYW20829B0-P4XXI100

CYW20829B0-P4XXI100 Bluetooth SoC (Figure 3) from Infineon Technologies comprises the 96 MHz Arm Cortex-M33 processor. The processor enables complex mathematical computation and minimizes power requirements for energy-sensitive applications. The memory protection unit acts as a robust security foundation for connected devices.

Figure 3. The CYW20829B0-P4XXI100 Bluetooth SoC from Infineon Technologies (Image: Infineon Technologies)

The module incorporates four fundamental elements: a crystal oscillator for precise timing, passive components for circuit stability, flash memory for program and data storage, and the CYW20829 silicon device, which serves as the primary processing unit. The 1 MB of onboard flash memory allows for the storage of extensive device configuration parameters, enabling more BLE applications.

This module supports Bluetooth 5.4 with improved range capabilities, enabling connections up to 500 m in optimal conditions. This extended range is particularly valuable for applications requiring broader coverage areas without adding repeaters or additional access points. The specification also supports higher data transfer speeds.

The high receiver sensitivity (down to -106 dBm) ensures reliable connections in large spaces or outdoor environments. The programmable transmit power of up to 10 dBm optimizes the range and power consumption balance.

The module’s power profile suits IoT devices that run on batteries. The efficient RX and TX currents of 5.6 mA and 5.2 mA, respectively, help the battery last as long as possible during active transmission. It can run long on battery power because deep sleep mode uses only 4.5 µA and hibernate mode uses only 0.5 µA.

The module has a compact package of 14.5 × 19 × 1.95 mm for space-constrained IoT devices. The castellated solder pad connections simplify manufacturing complexity and make it user-friendly. The wide operating temperature range (-40 °C to +85 °C) makes it suitable for indoor and outdoor applications.

Secure boot provides a comprehensive, multi-layered approach to preventing unauthorized code execution and maintaining system integrity across various computing platforms. Hardware acceleration and true random number generation address the additional security requirements.

The module comes with pre-existing certifications (FCC, ISED, CE, MIC Japan), significantly reducing the time and cost of bringing IoT products to market across multiple regions.

The module is available in two versions:

CYW20829B0-P4TAI100 with integrated trace antenna
CYW20829B0-P4EPI100 with RF solder pad for external antenna

Figure 4. The CYW920829B0M2P4TAI100EVK Evaluation Kit for quick testing and prototyping to develop Bluetooth applications. (Image: Infineon Technologies)

The CYW920829B0M2P4TAI100EVK Evaluation Kit, shown in Figure 4, supports standard Arduino headers, has programmable user buttons, an onboard six-axis IMU, and an onboard thermistor and mic to enable quick prototyping of Bluetooth applications. The Infineon GitHub has ample code examples to help you get started with the evaluation kit.

Summary

Silicon Labs’ EFR32BG26 and Infineon’s CYW20829B0-P4XXI100 are based on the 32-bit ARM Cortex-M33 processor, which optimally balances performance, energy efficiency, and security. With AI becoming a rising use case, EFR32BG26 offers a dedicated AI/ML accelerator feature in compact packages. However, Infineon’s CYW20829B0-P4XXI100 is a better choice for better processing speed, higher power, and wide certifications.

The next FAQ will continue to cover Bluetooth modules based on ARM processors from Texas Instruments and Quectel.