3 Design Comparison
Both displays used in these designs are equipped with an maXTouch® Touchscreen Controllers. Data communication with the touch controller is done using I2C. The touch controller will signal the host with a touch interrupt signal. To interface with the touch controller, PIC32CX-BZ6 uses a maXTouch driver, which can be added to the project graph and the driver code can be generated. The input system service acts as a bridge between the maXTouch® Touchscreen Controllers and the graphics software stack. The input system service dispatches touch events to graphics library listeners.
The frame buffer locations differ in both projects (in other words, stored internally for Bluetooth® Low Energy LCC and externally for external controller); however, in both designs, the fixed heaps and scratch buffers are stored in the internal data memory. The fixed heaps are used by the graphics library to store persistent data about widgets, fonts, and so on. The scratch buffer is also used by the graphics library as a temporary memory area used for intermediate data manipulation before rendering. The contents of the scratch buffer are then copied to the frame buffer (either stored internally for Bluetooth LE LCC or externally for the Bluetooth LE parallel 8080 design), which determines what is displayed on the LCD.
| Parameter |
Bluetooth® Low Energy LCC Project |
Bluetooth® Low Energy Parallel 8080 Project |
|---|---|---|
Color Depth | 8 bpp (RGB 332) | 16 bpp (RGB 565) |
Graphics Controller | Low-Cost Controllerless (LCC) graphics controller executing graphics functions internally. | ILI9488 graphics controller that completes graphics functions externally on the display panel |
Frame Buffer(1) | Located internally in data memory | Located externally on the display panel |
Scratch Buffer/Fixed Heaps(1) | Located internally in data memory | |
Timing Operations | Controlled internally and sent to display via GPIOs. The timer counter peripheral triggers the DMA and the completion of the transfer triggers the CCL to output the PCLK signal. | Controlled externally on the external controller. The timer counter peripheral triggers the DMA and the completion of the transfer triggers the CCL to output the Write Enable signal. |
Touch Operations | maXTouch® Touchscreen Controllers on external display communicates touch information to MCU via I2C. Touch events are sent from input system service to graphics library. | |
Note:
| ||