Bench Talk

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Embedded system designs all have one thing in common: a microprocessor and controller. These can be as sparse as 4-bit wide controllers with less than 1K of code space or as big as a multicore multi-GHz processing supercomputer with Gis of code space. But, modern IoT-based embedded system designs also have another typical requirement. Many designs will be mixed signals, so almost every design will include wireless communications.

Herein lies a challenge. Will a designer choose an overkill all-in open processor with much more performance, peripherals, memory, and processing power than is needed just to have a single integrated processor or dedicated functional processors to handle dedicated and specific tasks?

Both approaches may have merit depending on a variety of design constraints. Is time to market the driving force? Is cost the critical constraint? What about size or power efficiency? There are many factors and microcontrollers/microprocessors to choose from, especially as embedded systems invade our living space and become more prevalent. Nearly every place is now an intelligent environment.

Wireless Protocols

Every wireless device uses some sort of protocol to establish and maintain communications. While higher-cost, higher-end cellular protocols can be used for home and building communications, this carries the cost of a recurring monthly cellular fee. Modern 4G and 5G systems fall into this category, utilizing a range of wireless protocols for enhanced connectivity.

Wi-Fi^® is popular for media-based streaming and high-speed connectivity within a facility. Many Wi-Fi ICs and modules are readily available for designers in their embedded design. Still, many designs don't require the multi-Gbit/sec data rates or have higher power budgets to justify the more sophisticated and costly Wi-Fi medium.

Zigbee, Bluetooth^®, and LTE are the more power-friendly wireless protocols for room or building use. These require much less firmware, memory, and current, making them suitable for remote controls, lighting systems, media systems, temperature sensors, smoke/fire detectors, heating/cooling systems, and more.

What makes these protocols even more desirable is the topological flexibility they offer. In addition to point-to-point, these protocols can offer star, mesh, peer-to-peer, and client-server architectures. Star networks require each node to be in closer proximity to the star center, which is usually an aggregator. Peer-to-peer and mesh networks can “pass the baton” from node to node and cover longer distances since packets propagate along a routing path. This can also help preserve battery life since not a lot of transmission power is needed. Eventually, packets that are necessary for connecting to the World Wide Web will need to be routed to an access point. In all cases, security should be used.

Security

Sometimes, a security breach can be just an annoyance, like if someone hacks into your smart TV and changes channels. Other cases can be more serious, though, such as someone hacking into a home medical system. Handling these threats can be tackled in a few ways, but the most common strategy is encryption.

Many encryption algorithms and standards exist—some simple and some very complex. Wireless protocols like Zigbee and BLE have various methods of providing encryption protection. ZigBee uses 128-bit AES keys and is effective at applications layers as well as MAC layers. Bluetooth Low Energy (BLE) allows four layers of security:

• Level 1: No Security
  • Used for scenarios where data confidentiality is not a concern.
• Level 2: Unauthenticated Pairing with Encryption
  • Basic level of security, encrypting data transmission without verifying the identity of the connecting device.
• Level 3: Authenticated Pairing with Encryption
  • Enhances security with a method of authentication, such as a PIN, before establishing an encrypted connection.
• Level 4: Authenticated LE Secure Connections
  • The highest level of security in BLE, which uses an advanced encryption algorithm for authenticated pairing and secure connections.

Hardware-accelerated security functions can offload security functions from firmware and make processors much more desirable. Hardware encryption, decryption, hash code generation, pseudo-random sequence generators, and other blocks operate at lightning speed in hardware but take longer to implement in software. This adds latency time and requires the programmer to generate and debug more code.

In addition to runtime data protection, another layer of security needs to be in place, which is called a secure boot. With secure boot, boot loader firmware is protected and locked, preventing anyone from rewriting this critical code and redirecting its functionality. Normally, unprotected firmware feeds a processor when it boots. If it is replaced in flash somehow, the system is compromised. Secure boot takes advantage of strongly encrypted initial boot instructions, which then use digital signatures to authenticate the next layer of startup code.

A Dream Come True

Realizing the tightrope that designers have to walk when choosing an ideal microcontroller/microprocessor, many device makers are providing microcontrollers/microprocessors targeting this massive market for IoT, building automation, automotive, and industrial control. These applications need more than a simple processor but don't need a super processor. While development time needs to be quick, cost and size are generally high on the list of constraints.

One of the best ways to get the processors and peripherals you need is to use a system-on-chip (SoC) solution. These modular units can be made by an OEM for small quantity runs or used to prototype your own higher volume custom version.

The key is the 64MHz PIC32CX-BZ3 family of processors based on the 32-bit Cortex MF4 Arm. This processor brings a multitude of peripherals and its secure boot ROM checks integrity and authenticity before executing to ensure system root trust. There are also eight protected memory zones and a final fuse that makes it impenetrable.

The WBZ351 (Figure 1) drives the WBZ35x modules, which feature a fully compliant Bluetooth Low Energy 5.2 transceiver. The transceiver is also Zigbee 3.0 certified with software stacks built around the robust MPLAB Harmony v3 framework.

Figure 1: The peripheral-packed WBZ351 requires few external devices to implement the entire IoT or wireless design. (Source: Microchip Technology)

Also important are the hardware-based security accelerator and public critical hardware (Figure 2). The AES security encryption and HASH code generator are also included to create a secure execution environment. Anti-rollback and firmware readable life cycle encounters offer even more levels of protection.

Figure 2: The WBZ351 module contains all the processing horsepower and peripherals needed to support smart homes and buildings, industrial control and monitoring, and wireless IoT applications. (Source: Microchip Technology)

Conclusion

When it comes to the IoT and smart environments, designers have a big job. They must integrate wireless connectivity with strict security measures. That’s where Bluetooth Low Energy and Zigbee come in. These solutions can cover large areas with mesh networks while consuming less power. By incorporating secure boot and capacitive touch functionalities, designers can accelerate concept-to-market and allow designers to meet the demands for security and user interaction in today’s IoT devices.

The PIC32CX-BZ3 family of processors packs everything needed into one place, including advanced connectivity options and hardware-based security features. By leveraging powerful solutions, designers can navigate complex modern IoT ecosystems to ensure smart environments are intelligent, secure, and user-friendly.

Author

After completing his studies in electrical engineering, Jon Gabay has worked with defense, commercial, industrial, consumer, energy, and medical companies as a design engineer, firmware coder, system designer, research scientist, and product developer. As an alternative energy researcher and inventor, he has been involved with automation technology since he founded and ran Dedicated Devices Corp. up until 2004. Since then, he has been doing research and development, writing articles, and developing technologies for next-generation engineers and students.