A survey of Bluetooth connectivity modules for IoT applications: part 3

Microchip Technology and Qualcomm have their own proprietary SoC in their Bluetooth modules. In this third part of the FAQ series, we discuss the RNBD350 and QCC711 Bluetooth low-energy (BLE) modules and explore their development kits.

Microchip Technology: RNBD350

The RNBD350 is a compact BLE 5.2 module based on Microchip Technology’s PIC32CX-BZ3 SoC, designed to provide a comprehensive solution. Low-energy operation is important for battery-operated devices that must operate for extended periods without frequent recharging. Figure 1 shows the BLE module and the associated block diagram.

The module can interface with a host MCU or MPU via a Two-Wire or Four-Wire UART interface. While the Two-Wire UART interface uses only TX and RX wires, reducing complexity in hardware design, the Four-Wire UART interface adds two additional control lines and provides additional hardware flow control mechanisms.

A host can use simple commands or change to a standard Bluetooth HCI mode to dynamically set up the RNBD350 module.

In the Host Controller Interface (HCI) mode, standardized device communication enables automatic device detection, supports power management, and facilitates seamless interaction between the host and devices.

ASCII Command Interface is a simplified communication method over UART that uses human-readable text commands, simple debugging, and a quick understanding of device communication.

The built-in Microchip Transparent Profile for UART data streaming enables efficient real-time serial data transmission. It supports bi-directional data exchange between devices and modules. In addition, over-the-air (OTA) configuration updates firmware remotely without physical access to the devices.

The stack provides advanced 2M Uncoded physical layer (PHY) capabilities, doubling data transmission rates. Long Range (Coded PHY) supports extended signal transmission and reception performance without increasing transmission power. Data length extensions allow larger data transfers in a connected state to improve overall data transmission efficiency.

The 16 MHz crystal oscillator provides highly stable frequency generation with exceptional characteristics. Its integrated 12-bit analog-to-digital converter (ADC) allows direct sensor data conversion, enhancing its utility in IoT sensing applications and reducing component count.

The support for multiple roles (advertiser, observer, central, and peripheral) provides flexibility in designing IoT networks, allowing devices to act as data collectors and distributors as needed. The module’s multi-link and multi-role capability supports up to six concurrent connections and enables the creation of small mesh networks of IoT sensors.

The RNBD350 module operates in the 2.402-2.480 GHz ISM band with programmable transmit output power up to +11 dBm and receiver sensitivity of -108 dBm across 125 Kbps BLE data rates.

Secure connections provide authenticated pairing. The BLE privacy 1.2 feature is particularly important for IoT security, helping protect sensitive data in applications like medical devices or smart home systems.

The module has the ability to operate across a typical 3.3 V supply. The extended temperature range from -40 °C to +85 °C enables deployment in challenging industrial settings, outdoor environmental monitoring, automotive applications, and extreme climate conditions.

The RNBD350 Add On Board, shown in Figure 2, is an easy-to-use platform that enables speedy design concepts with the BLE module. The mikroBUS Socket and USB Type-C interface allow interconnection between the host board and host PC. The board is fully supported by MPLAB X Tools and MPLAB Harmony v3 with example applications.

Qualcomm: QCC711 BLE SoC

Qualcomm’s QCC711 BLE SoC is the first Bluetooth device with three microcontroller cores to be made official, supporting the latest Bluetooth 5.4 standard and BLE. The three cores of the SoC are as follows:

32MHz Arm Cortex-M3 for application processing
32MHz Arm Cortex-M0 dedicated to Bluetooth operations
32MHz RISC-V Root-of-Trust (RoT) processor for security

It contains 128 KB of SRAM for general processing and 512 KB of RRAM (Resistive RAM), a non-volatile memory technology, eliminating the need for external flash storage. It simplifies the overall design, reducing the number of components required on the PCB. This can lead to lower manufacturing costs and a more compact design. Figure 3 shows the block diagram of the QCC711 BLE SoC, where the features are categorized into Bluetooth, application, security, and peripheral subsystems.

Figure 3. Block diagram of the QCC711 BLE SoC with its various subsystems. (Image: Qualcomm)

An excellent receiver sensitivity (down to -103 dBm for 125 kbps) ensures reliable communication in smart buildings or industrial settings. The module can achieve better signal strength by transmitting power of 16.6 mA at +6 dBm, reducing loss and improving overall communication reliability. This combination of low transmit power and receiver sensitivity enables longer battery life in wireless sensor networks and portable devices.

The QCC711’s dual operating modes provide flexibility in IoT implementations. The hostless mode is particularly valuable for simple IoT devices that must operate independently, while the hosted mode enables integration with more complex systems.

The Hardware-Based Security Subsystem includes a dedicated RoT CPU with secure boot, secure debug, encrypted storage, and key provisioning capabilities. The RoT processor ensures a secure environment with Trusted Execution Environment (TEE), Hardware cryptographic acceleration, and OTA updates.

The wide operating temperature range (-40 °C to +85 °C) and compliance with international standards make this module suitable for deployment in harsh industrial environments and outdoor installations. It comes with various international standards, including FCC, CE, and RoHS.

The compact dimensions (12.8 x 18.82 x 2.2 mm) and minimal weight (1.05 g) allow for integration into space-constrained IoT devices such as asset tracking beacons, smart health devices, remote controls, smart switches, and building automation systems.

Figure 4. Component layout of the QCC711 Module Development Kit. (Image: Meruti)

The Qualcomm QCC711 Module Development Kit shown in Figure 4 is a breadboard-friendly development kit with dual headers allowing for flexible expansion with other sensors and accessories. The kit has 26 generic PIOs, out of which four are analog-in-configurable. An open-source software development kit is available on GitHub, along with a VSCode-based Integrated Development Environment (IDE) tailored for the development kit.

Summary

The BLE modules from Microchip Technology and Qualcomm have built their proprietor SoC for their Bluetooth module, which allows customization. The RNBD350 can be set into HCI mode or used in the ASCII Command Interface for flexibility. The QCC711 BLE SoC is unique in terms of multiple microcontroller cores that split the tasks into respective cores for faster processing. These modules suit smart building, industrial IoT, and asset-tracking applications.

The next and last part of the FAQ series will cover STMicroelectronics and Nordic Semiconductor Bluetooth modules.