Connected MCUs Simplify Wireless IoT Design with Integrated Processing, Connectivity, and Security

Technical Overview: Connected MCUs combine processing, wireless connectivity, security, memory, and I/O to reduce component count and design complexity. This article examines Infineon AIROC CYW55912/3 MCUs and Ezurio Veda modules, which support hosted or hostless operation, low-power wireless performance, and flexible interfaces. (Overview courtesy of ChatGPT)

Connected medical devices, Industrial IoT (IIoT) applications, smart home nodes, and commercial products all need processing capability, wireless connectivity, low power consumption, and security. Engineers designing such systems used to have only two choices: use multiple chips that take up more space and power to accomplish all the desired functions, or select a compact integrated edge device with less processing power.

A connected microcontroller unit (MCU) bridges this gap by integrating the functions of multiple chips into a single device, with processing power sufficient for even the most demanding applications. This article will discuss connected MCUs, their performance capabilities, integration into connected products, and the tools available to speed deployment.

Comprehending connected MCUs

A connected MCU is a single device that combines wireless connectivity, memory, security, I/O peripherals, and processing. Infineon Technologies AIROC™ CYW55912/3 chips (Figure 1) are connected MCUs that contain an Arm® Cortex®-M33 processor and support Wi-Fi 6/6E and Bluetooth Low Energy (LE) in a 3.57 × 5.32 mm wafer-level ball-grid array (WLBGA).

Figure 1: The Infineon AIROC CYW55913 connected MCU integrates processing, communications, security, and power management subsystems. (Image source: Infineon)

Connected MCUs work in a hosted or hostless mode. A connected MCU in hosted mode can also be called a network co-processor (NCP). In this architecture, a separate processor does the heavy computing and controls the connected MCU, which manages wireless communication. In hostless mode, the connected MCU acts as a system-on-chip (SoC). The MCU’s processing core becomes the primary processor, running all applications, stacks, and security protocols within the connected MCU device.

Package performance particulars

Hostless operation is possible with processors such as the Arm Cortex-M33, which runs at 192 MHz, especially when combined with the 768 KB of static random-access memory (SRAM) and 2.0 MB of read-only memory (ROM) included in AIROC CYW55912/3 connected MCUs (Figure 2).

Figure 2: The block diagram of an AIROC CYW55913-connected MCU shows its processing, radio, power management, security, memory, and I/O subsystems. (Image source: Infineon)

The dedicated power-management subsystem in these connected MCUs keeps power consumption low and manages low-power sleep modes. AIROC CYW55912/3 MCUs also support 802.11ax target wake time (TWT), a power-saving feature that defines specific times when the device wakes to communicate. The combined efficiency makes the devices suitable for wearable and battery-operated applications.

The MCU’s ROM stores software from Infineon, including a NetX DUO TCP/IP networking stack, NetX Secure software supporting Transport Layer Security (TLS) 1.3, and the ThreadX real-time operating system (RTOS), which schedules, synchronizes, and manages tasks. Customer application software can be stored in external flash memory and execute-in-place (XIP) through the chip’s quad serial peripheral memory interface (QSPI/SMIF) with on-the-fly (OTF) 128-bit encryption and decryption.

Other security features on the AIROC CYW55912/3 include a hardware root of trust, secure boot, secure key management, secure one-time programmable (OTP) memory, anti-rollback protection, and hardware cryptographic acceleration. These connected MCUs also support Wi-Fi security via Wi-Fi Protected Access (WPA) 2 or 3 in personal or enterprise configurations.

Wi-Fi security protects this key function of connected MCUs. The AIROC CYW55913’s tri-band capability allows it to access the less congested 6 GHz spectrum for greater throughput and potentially lower latency, in addition to transmitting at the 2.4 and 5 GHz frequencies available to the AIROC CYW55912’s dual-band radio. Receive sensitivity varies with frequency, data rate, and the way signals are encoded. AIROC CYW55912/3 transceivers can detect signals as weak as -101.5 dBm at 2.4 GHz and 1 Mbps using DSSS. At 5 GHz, sensitivity is -94.5 dBm at MCS0.

Both the AIROC CYW55912 and AIROC CYW55913 have RF output power up to +24 dBm at 2.4 GHz and 1 Mbps using DSSS. They employ Wi-Fi 6/6E techniques such as high-efficiency extended-range physical protocol data unit (HE ER-PPDU) physical layer (PHY) encoding, long guard intervals, and dual-carrier modulation (DCM) to make Wi-Fi transmissions more robust, especially at the edge of coverage.

AIROC CYW55912/3 connected MCUs route Bluetooth signals over +4 dBm, +13 dBm, and +19 dBm power paths, optimizing efficiency or providing sufficient signal power to accommodate poorer antenna performance or longer-range requirements. The devices support Bluetooth LE PHY standards for 1 Mbps (LE 1M), 2 Mbps (LE 2M), and long range (LE LR), as well as advertising extensions. Internal low-noise amplifiers (LNAs) and power amplifiers (PAs) contribute to networking performance; external amplifiers are supported when higher RF performance or range is needed.

Real-world integration

In addition to wireless communications, AIROC CYW55912/3 connected MCUs support multiple I/O configurations. Secure digital I/O (SDIO) 3.0, generic serial peripheral interface (gSPI), universal asynchronous receiver/transmitter (UART), and inter-integrated circuit (I²C) protocols allow the MCU’s processor to communicate with external processors and peripherals. SDIO and gSPI high-speed protocols are most often used in hosted mode; UART and I²C are simpler, slower protocols frequently used for control signals and sensor communication.

AIROC CYW55912/3 MCUs handle audio signals using inter-IC sound (I²S), time division multiplexing (TDM), pulse density modulation (PDM), and pulse code modulation (PCM). They also have a 12-bit analog-to-digital converter (ADC) with seven input channels, and up to 47 general-purpose I/O (GPIO) pins can be configured to send basic on-off signals for the application.

The multiple wired and wireless digital signals being transmitted in and around a connected MCU can produce unwanted RF interference if the device is not properly designed. Integrated modules like the Veda IF912 and IF913 (Figure 3) from Ezurio incorporate AIROC CYW55912 and AIROC CYW55913 MCUs, respectively, into an RF-engineered device complete with antennas, shielding, and additional memory.

Figure 3: Ezurio’s Veda IF912 (a) and IF913 (b) modules incorporate AIROC CYW55912/3 MCUs, antennas, shielding, and memory in a single device. (Image source: Ezurio)

The Veda IF912/3 modules are designed with layout, shielding, and impedance matching in mind. Some Veda variants are system-in-package (SiP) modules that combine 8 MB of flash memory, 8 MB of pseudo-static RAM (PSRAM), and the AIROC CYW55912/3 WLBGA MCU. Other variants support the addition of equivalent external memory. SiP integration simplifies high-speed memory connections, lowers component count, and enables compact designs.

Despite the addition of RF circuitry, shielding, and external memory, Veda module packages are compact, measuring 7 by 11 by 1.4 mm. Their small size makes it easier to lay out an application’s PC board (PCB) with the Veda module, power modules, sensors, and display hardware. Their surface-mount (SMT) design supports manual or automated soldering processes.

Ezurio provides regulatory certifications and approvals for many markets, including FCC, ISED (Canada), CE, UKCA, RCM, MIC, and KCC, as well as Bluetooth SIG qualification. This documentation, along with approved antenna configurations, helps simplify the compliance process.

Reference hardware designs further simplify integration for design engineers. For example, Ezurio provides RF circuit layouts for an embedded PCB trace antenna, shared Wi-Fi and Bluetooth antenna RF connections, and a connection from the Veda IF912/3’s RF trace pin to an MHF4 connector for an external antenna.

Closing the loop with coding

In addition to hardware reference designs, engineers can access application development support from Infineon and Ezurio. Infineon’s ModusToolbox development ecosystem includes a comprehensive library of software tools, wireless stacks, middleware, and drivers that engineers can integrate into their projects, enabling them to develop application-specific code rather than reinventing complex stacks.

Ezurio also has code examples and resources specific to the Veda IF912/3 modules, such as code for Wi-Fi scanning and Wi-Fi provisioning over Bluetooth LE. These help engineers move from the ModusToolbox development environment to a working application. Other module-specific resources help engineers configure, develop, test, program, and debug their connected MCU applications. Tools like these and ModusToolbox, combined with technical documentation and expert support for integration and regulatory questions, shorten application development cycles and reduce costs.

Conclusion

Ezurio’s Veda IF912/3 modules and the Infineon AIROC CYW55912/3 connected MCUs within them give engineers the flexibility to use the modules as an RF-engineered NCP in a compact package or deploy them as connected SoCs with sufficient computing power for a variety of applications. The reduced component count, approved antenna configurations, reference designs, and coding resources enable designs using these modules to reach market faster and at lower cost, delivering integrated processing power, connectivity, and security to IoT and IIoT applications, medical devices, wearables, and handheld devices.