Distributed Intelligence
IIoT implementations are highly intelligent. With the miniaturization of electronics and the rapid growth in computing performance, more PLCs are processing data locally and the “thinking” is being pushed deeper into the system. Even sensors are becoming more clever, undertaking significant data processing before data is passed up and through the network. But powering these sensors delivers challenges, with the expectation that Power-over-Data Line (PoDL) can be used even for Single Pair Ethernet (SPE) implementations. This can limit allowable power consumption to the 500- to 800-mW range.
Embedded Linux® offers a wealth of functionality supported by the open-source community, ensuring that standard capabilities, such as file systems and connectivity, are ready to go. This leaves development teams able to concentrate primarily on their application and its functionality. But the type of hardware needed for this operating system does not typically fall in the domain of low power.
Learn More About Linux OS for MPUs
This all changes with the SAMA5D2 and SAMA5D3 series of MPUs. These MPUs feature Arm Cortex-A5 processors that can be clocked at up to 500 or 536 MHz, respectively, and contain 128 kB of SRAM and 2 × 32-kB L1 caches. SAMA5D2 MPUs also feature 128 kB of L2 cache. In active mode and with all peripherals in use, these devices draw less than 150 mW of power while the low-power mode with SRAM and register retention see this drop to under 0.5 mW. These MPUs are also unique in running Linux and integrating Profinet, OPC-UA and TSN/T1S in a single chip with the lowest power.
If more performance is required, there is room to grow with the SAMA7G5 series. Operating at up to 1 GHz, they utilize the Arm Cortex-A7 complete with TrustZone, a floating-point unit, and level 1 and 2 caches. Dual Ethernet (gigabit and 10/100) along with six CAN-FD provide plenty of connectivity, and high-performance crypt accelerators simplify the implementation of IEC 62443. At room temperature, processor power consumption lies under 350 mW at 1 GHz, while a camera application streaming over Ethernet requires under 670 mW. The rich range of ultra-low-power modes can draw as little as 9 mW (25°C) depending on the wake-up response time required.
Microchip has supported mainline Linux with the kernel, bootloader and drivers under development since 2004 and shares these components through the linux4sam.org website. The Long-Term Support (LTS) kernels provide maintenance for up to six years. Embedded applications can also be built using the tools provided by the Yocto Project and Builtroot is also supported. AT91bootstrap provides a second-level bootloader that can pass control to U-Boot.
You can get started using the ATSAMA5D27-SOM1-EK1, a fast prototyping and evaluation platform that combines the SAMA5D2 MPU with 1 Gb DDR2 DRAM, power management, 64 Mb QSPI Flash and 10Base-T/100Base-TX Ethernet in module form. The kit also provides a 12-bit camera interface and mikroBUS™ connectors to expand functionality.
ATSAMA5D27-SOM1-EK1
While you can use Linux to tackle a wide array of embedded applications and take advantage of the real-time support when using the PREEMPT_RT patch, there are occasions where a dedicated MCU that features a real-time kernel is needed. Solutions like FreeRTOS provide exceptional documentation and integrate ready-to-run examples into the MPLAB development environment. Fulfilling functional safety criteria is simplified with Azure RTOS ThreadX, a real-time operating system with pedigree.
Alternatively, Zephyr offers a compact kernel for SAM D, E, L, R, and V MCUs, along with protocol stacks for connectivity and support for firmware updates. Microcontrollers in these series, like the SAME7x family with its Arm Cortex-M7 processor, provide a similar connectivity offering as their Linux-capable cousins, including 10/100 Mbps Ethernet with IEEE 1588, dual CAN-FD, and a USB device/host.
32-bit Low-power MPUs
Linux4SAM
Datasheet: RTOS Support with MPLAB Harmony
