With features such as an advanced controller, optimized for small, circular displays, that boosts pixel-handling efficiency; and a power-saving architecture enabling richer functionality with longer battery life, this new generation of the STM32L4 series stretches performance to 150 DMIPS (233 ULPMark-CP) at 120 MHz. The MCUs can be the central controller in a full range of fitness bands, smart watches, small medical equipment, smart meters, and smart industrial sensors. All these applications require sophisticated functions, instant responses, and minimal downtime for battery charging, matched by the ultra-efficient STM32L4+.
STM32L4+ has processor performance together with the largest on-chip memory for this type of ultra-low-power microcontroller, and the most advanced graphics capabilities for smooth and fluid user experiences. The new Chrom-GRC graphics controller can handle circular displays (TFT-LCDs) just as efficiently as square ones, without wasting resources managing pixels that are never displayed. Also on-chip is ST’s innovative Chrom-ART Accelerator, which enhances graphics performance. (more architecture details; next page)
“We all now expect smart objects to fit seamlessly into our lives, anticipating our needs, yet requiring minimal attention themselves,” said Michel Buffa, Microcontroller Division General Manager, STMicroelectronics. “Leveraging the controllers’ largest-in-class memory and super-efficient graphics capabilities, STM32L4+ microcontrollers series will enable new classes of smart products with more sophisticated features and smoother interactions.”
Designers using the STM32L4+ series can use the extensive STM32 development ecosystem, which helps streamline design and minimize time to market. The ecosystem provides affordable prototyping boards, software examples, free tools, and high-quality third-party software, hardware, and integrated development environments (IDEs) as part of the ST Partner Program. Applications developed for the earlier STM32L4 microcontrollers can run unchanged on the new devices, with improved performance.
The STM32L4+ devices, in various package options start at $6.52 (10,000).
The STM32L4+ is the latest in the STM32 family. “L” stands for ST’s ultra-low-power design features and modes, which combine to ensure the chip always consumes the least possible energy. “4” describes the high-performing Arm Cortex-M core. And “+” signifies more compute performance, more memory, more features on-chip, and more efficient, high-performing graphics for the latest product designs.
The enhanced memory capabilities include dual Octo SPI ports, making these the first STM32 devices to support this interface. The dual ports allow cost-effective and high-speed extension of code or data storage using single/dual/quad/octal SPI, or HyperBus, Flash or SRAM memories.
The advanced power-saving technologies include proprietary FlexPowerControl, which protects important data like SRAM contents and I/O-pin states when the device is in low-power modes. FlexPowerControl also provides for separate power-supply domains that allow individual voltage adjustment and power-down to meet processing loads at the lowest possible energy, and a programmable high-accuracy clock that saves external components and minimizes power consumption when operating at reduced frequency. In addition, seven main low-power modes, each with optional sub-modes, help optimize for low-power consumption, short startup time, available peripherals, and available wake-up sources. Among these modes, the shutdown mode reduces the current to 20 nA. All STM32L devices also support batch-acquisition mode, which encourages energy-efficient data capture and storage in low-power modes with the main CPU turned off.
The on-chip memory of STM32L4+ devices includes 640 kBytes of SRAM to assist high-speed computation and help maximize graphics performance. In addition, the devices in this series provide up to 2 MBytes of dual-bank Flash memory, giving extensive code and data storage with efficient read-while-write capability. These are the largest memory densities available among ultra-low-power microcontrollers in the market today. The Flash also has extensive error-correction features, suitable for use in safety-conscious applications.
ST’s Chrom-ART Accelerator (DMA2D) offloads repetitive 2D-graphics calculations from the main CPU. It can perform 2D copies, transparency and alpha-blending operations, as well as pixel format conversions, two times faster than the main CPU. The saved CPU cycles can be re-allocated for real-time processing, running concurrently with the graphic operations, or to handle even more impressive graphic effects.
The Chrom-GRC graphics memory manager allows users to “unsquare” circular displays, reducing graphics-handling workload by up to 20%. From a memory stand-point, circular displays are often managed in the same way as square displays, which wastes memory by handling pixels that are never displayed. The STM32L4+ Chrom-GRC allows more efficient management of memory resources by handling useful pixels only.
There are also rich digital and analogue features, including extensive USB support with Host, Device, and OTG capabilities, 17 timers for functions such as motor control, digital communication interfaces including SPI, SAI, CAN, and high-speed digital filters for signal processing.
The analogue peripherals include high-speed analogue-digital converters (ADCs), digital-analogue converters (DACs), and precision voltage references, comparators, and op-amps. All are architected to maximize energy efficiency in any operating mode, such as by powering down converters in between capturing samples.
The STM32L4+ series is also available in a high-temperature version, specified up to 125°C, which can be used in confined environments where heat dissipation may be impaired.
Developers can take advantage of a wide variety of ecosystem elements, that include the 144-pin STM32L4+ Nucleo board (NUCLEO-L4R5ZI) with Arduino Uno V3 and ST morpho expansion connectivity, and probe-free debugging. The more fully-featured STM32L4+ Discovery Kit (STM32L4R9I-DISCO) lets users develop and share applications, and contains 24 bpp round LCD
(1.2 inch, 390×390 pixel), 16-Mbit on-board PSRAM and 512-Mbit Octo-SPI Flash memory interface, MEMS microphones, and an audio codec to enhance the audio graphics performance of a wide range of applications. Arduino, Pmod, and STMod+ connectivity provide extra expansion options.
The STM32L4+ evaluation kit (STM32L4R9I-EVAL) is a complete demonstration and development platform for evaluating all the microcontroller peripherals and building applications.
The associated embedded software and tools are based on ST’s STM32Cube platform. This comprises the STM32CubeMX initialization-code generator and configurator with power estimation, and the STM32CubeL4 software package.
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