Add graphics without using a dedicated graphics controller
Adam Folts, Microchip Technology
EETimes (11/8/2011 11:48 AM EST)
As embedded applications continue to deliver ever more flexible and powerful user interfaces, the need to include a graphical interface in a design puts pressure on the designer trying to keep costs low. A typical system with a graphical display relies on an internal or external graphics controller to drive the display, but this can increase the complexity of the design and add cost. For a simple graphical interface, the extra cost for a graphics controller may not be justifiable. However, some microcontrollers include a mix of peripherals coupled with a specialized graphics library, which enables designers to incorporate simple graphical interfaces without incurring the cost of a dedicated graphics controller.
A low-cost, controllerless approach is to use a microcontrollers peripherals and memory resources as a substitute for a graphics controller, thus creating a virtual graphics controller that can render graphics and continuously update an LCD display, while consuming approximately six percent of the total CPU bandwidth.
A microcontroller only needs Direct Memory Access (DMA) and Parallel Port Master (PMP) peripherals to create a virtual graphics controller. This approach is appropriate for use in cost-sensitive consumer applications such as thermostats, cordless phones, remote controls, coffee machines, washing machines, and ovens. It may also be appropriate for commercial and industrial applications such as ATMs, digital instrument gauges, storage controls, remote terminals, and movie-rental boxes. Medical applications that can benefit from a controllerless graphics display include glucometers, blood-pressure monitors, and portable Electrocardiograms (ECGs).
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