8-bit microcontrollers target in-cabin touch interfaces

November 23, 2016 // By Christoph Hammerschmidt
Cars are equipped today with an increasing number of motors to adjust things like headlights, seats, rear view mirrors and more. Silicon Labs has introduced two families of automotive-grade EFM8 microcontrollers (MCUs) designed to handle such body electronics motor controls and similar applications via touch interface.

The new AEC-Q100-qualified, ultra-low-power EFM8SB1 Sleepy Bee family provides advanced on-chip capacitive touch technology enabling easy replacement of physical buttons with touch control. The EFM8BB1/BB2 Busy Bee family features high-performance analog and digital peripherals, making these devices a versatile choice for controlling motorized in-car equipment. All EFM8 MCUs deliver best-in-class 8-bit performance through a combination of advanced features and capabilities including a high-speed pipelined 8051 core, ultra-low power, precision analog and enhanced communication peripherals, on-chip oscillators, small-footprint packages, and a patented crossbar architecture that enables flexible digital and analog peripheral multiplexing to simplify PCB design and I/O pin routing.


EFM8SB Sleepy Bee MCUs are the vendor’s most energy-friendly 8-bit devices offering high touch performance, ultra-low sleep-mode power (50 nA with full memory retention and brown-out detection) and fast 2 µs wake-up time. The automotive-grade EFM8SB1devices support -40 to +85°C ambient temperatures, core speeds up to 25 MHz and flash sizes up to 8 kB. The MCUs integrate a 12-bit analog-to-digital converter (ADC), high-performance timers, a temperature sensor, and enhanced SPI, I2C and UART serial ports. An on-chip high-resolution capacitive-to-digital converter (CDC) offers an ultra-low < 1 µA wake-on-touch capability and 12 capacitive touch channels, eliminating the need for on/off switches in many applications. The MCUs are ideal for touch-based controls such as dome lights and overhead buttons. Capacitive touch control provides a more durable, moisture-resistant user interface and a sleeker look and feel for today’s electronics-laden vehicles.


Silicon Labs supports touch-sense interface design with its Capacitive Sense Library available within the Simplicity Studio development tool suite, offering all features and algorithms required to add capacitive sensing interfaces to automotive applications. Simplicity Studio provides designers with production-ready firmware, from scanning buttons to filtering noise. By using the Capacitive Sense Profiler to visualize real-time data and the noise levels of cap-sense buttons, developers can customize touch and no-touch thresholds and noise filtering settings, simplifying the addition of capacitive touch to