Multi-touch all-point refers to a touch-sensing surface’s (trackpad/touchscreen) ability to recognize the presence of two or more points of contact on the surface at the same time. Users have 10 fingers across two hands, and presence of multiple passengers in a car further increases that number. Music browsing, map manipulation, and body electronic controls like seat position are a few examples of automotive applications that are prime candidates for this level of rich touchscreen functionality.
Trackpads in cars make it convenient for the driver to operate systems such as the navigation and audio subsystems without having to stretch out to reach the center console. Trackpads also enable character recognition, making alphanumeric keys redundant.
A touchscreen typically has a glass/plastic covering overlay along with two layers of transparent conductors such as Indium Tin Oxide (ITO) that are separated by an insulating material. Patterns are etched on the ITO layer to form a grid of capacitors. The ITO layer has a high level of transparency that helps make the touchscreen brighter and easier to read. Since there is no pressure required for detecting touch, the screen becomes more durable.
In a trackpad, the capacitive sensor construction is similar except that the system has an opaque covering layer and simple copper layers as sensors.
The touchscreen’s sensors are scanned in order to detect any change in sensor capacitance to detect any finger touches. The data is analyzed to identify gestures, finger range, and finger direction movement. The system may also drive output devices like LEDs or control motors.
Capacitive touchscreens and trackpads with 10-finger support are now increasingly being adopted in cars, serving as the integrated interface for various car systems. These multi-touch all-point sensing systems also allow multiple users within a car to simultaneously access the touchscreen. In addition, automotive networking protocols like CAN/LIN help integrate distributed electromechanical systems into a central console. This enables HMI designers to coordinate operation of all subsystems within the console from a single user interface to create an HMI with a unified style and increased flexibility, while offering developers greater control over look and feel.
Aditya Kaul is product marketing engineer with Cypress Semiconductor.