Development of a touch screen display with haptic functionality and a graphical user interface in a heterogeneous multi-core and multi-processor environment

The haptic perception is the tactile sensation obtained as a result of interaction with surfaces and objects. This sense of touch can be artificially recreated by stimulating the human body through feedbacks, such as the vibration given by the smartphone after a long press. The aim of this thesis was to apply haptic functionality to a touch screen display and to develop a graphical user interface (GUI) that shows the potentiality of this product. The measure of the force and the stimuli generation, main actors in the haptic perception, were made using an actuator, the Niceclick, which thanks to an ad-hoc circuit transforms, when a force is applied, its magnetic reluctance variation into a pulse that can be easily read by a microcontroller. In addition, the actuator can also generate a sequence of pulses making up the haptic feedback. For these reasons, the generation of the haptic feedback can be done by checking if the force applied on the surface exceeds a settled threshold or generates it immediately once the presence of the finger, or a gesture, is confirmed. The firmware of the microcontroller works in a real time environment to make the haptic management and the operative tasks precise and repeatable. The operative task consists in the reception of commands, coming from the CAN Bus, their interpretation to perform specific operations and giving back the feedback status. This workflow is necessary because the display is managed by another processor, the iMX8M mini, which uses the external microcontroller as a slave sending commands or requests to manage the haptic part. The iMX8 processors are a family of heterogenous multi-core processors, where two different types of cores work in the same environment, sharing peripherals and memory portion. In this processor there is the Cortex A53 in charge to manage the graphic part of the application and the Cortex M4 that acts as microcontroller with a real time OS. The latter is used as interface between the graphic processor and the external microcontroller, passing the information back and forth managing the CAN communication. Finally, the developed GUI display different interfaces that show the potentiality of this technology: an automotive dashboard, where the sense of press and release of a switch can be felt, images where a texture is perceived and a configurable panel where the force threshold and haptic effect could be changed. Another goal of this thesis was to verify if the iMX8M mini could manage the entire system on its own, in other words, if the Cortex M4 could also perform the work done by the external microcontroller, while A53 handles the graphics. To conclude, this study confirmed that M4 can handle the haptic part, giving improvement from the communication and computational point of view, however there is a lack of a peripheral which can be compensable readapting the control circuit using external IC.