GUI design for ultra-low-cost devices with TouchGFX

13th October 2020
Alex Lynn

STMicroelectronics is helping the HMI of things with a new STM32 Nucleo display shield that leverages the affordability of STM32G0 microcontrollers (MCUs). The new X-NUCLEO- GFX01M1 SPI shield is supported in the latest TouchGFX software, version 4.15.0, which introduced additional new features including support for low-cost non-memory-mapped SPI Flash ICs.

Designing with STM32G0 and TouchGFX lets developers target a bill of materials as low as $5 to add a small graphical display to any project. Simple devices such as timers, controllers, and home appliances can thus offer a smartphone-like user experience.

The new X-Nucleo-GFX01M1 shield is supported by a new X-cube-display package that offers simple ‘hello world’ example. The shield contains a 2.2” QVGA (320x240) SPI display, 64-Mbit SPI NOR Flash, and a joystick and is ready to use with various STM32 MCU development boards such as the NUCLEO-G071RB. The STM32G071RB is a mainstream Arm Cortex-M0+ MCU that integrates up to 128kBytes Flash, 36kBytes SRAM, extensive communication interfaces, analog peripherals, fast I/Os, hardware security ID, and a USB Type-C Power Delivery controller.

The latest TouchGFX software builds on the TouchGFX Engine’s partial framebuffer, which can reduce the GUI RAM footprint by up to 90% and allow a simple user interface in as little as 16-20KB of internal MCU RAM. A new rendering algorithm enhances GUI performance by realising partial screen updates in an optimised order to allow extra updates and avoid visually distracting tearing effects. Also new, support for non-memory-mapped SPI Flash allows more complex GUIs to use low-cost off-chip storage for memory-hungry graphics assets such as images and fonts.

To ease user-interface prototyping, an optimised application template for the STM32G071 Nucleo board and display kit is available in TouchGFX Designer. It is also possible to introduce an RTOS to the setup if required and use TouchGFX Generator to change to other hardware.

All elements are available now, including the X-cube-display package and TouchGFX 4.15.0 with code examples for running the G071RB. The X-NUCLEO- GFX01M1 and STM32G0 products are in mass production and available through the normal ST distribution channels.

In addition, a new graph widget simplifies showing sequential data using lines, bars, area plots, histograms, or combined visualisations. The widget works smoothly with any STM32 MCU and developers can customise aspects such as colors and layout using TouchGFX Designer.

Also new in TouchGFX 4.15.0, full out-of-the-box support for the STM32H725 lets developers run microprocessor-class graphics on ST’s Cortex-M7 MCUs. With 550MHz core frequency, ST’s Chrom-ART Accelerator for faster graphics performance, an Octal-SPI interface for high-speed connections to external Flash and RAM, and an XGA TFT-LCD controller, the STM32H725 is the new graphics flagship for the STM32 family.

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