Display Resolution
The BT817/BT8188 supports LCD displays with a total of up to 1 megapixels and up to 2048 pixels per line.
Their flexible timing supports LCD resolutions of 1920x480, 1440x540, 1280x800, 1024x600, 800x600, 800x480, 480x272, 320x240 and many more.
Dedicated PCLK PLL and 2X Pixel Mode
BT817/BT818 has two independent PLL loops that generate clock frequencies SYSCLK and PCLK from the crystal oscillator.
PLL1 generates SYSCLK clocks for all internal circuits, including the graphics engine, audio engine and touch engine. The PCLK PLL (PLL2) generates clocks for the RGB interface when configured in Exsync mode. This allows independent setting of PCLK and SYSCLK. The PCLK frequency can be higher than the SYSCLK, up to 96 MHz.
If PCLK >= SYSCLK, REG_PCLK_2X needs to be 1 so that the graphic engine will send 2 pixels per SYSCLK to the EXTSYNC block.
Non Square Pixels Support
We will explain the principle of operation with an example.
A popular panel LCD resolution is 800×480. This gives a logical aspect ratio of 800/480 = 1.6667. However, the physical size of the panel is 153.84 × 85.63mm, giving an aspect ratio of 1.796. This difference means that the panel has non-square pixels. So we can compute the logical width of the panel while keeping the height constant:
480 × (153.84/85.63) = 862.3
So when rendering a graphic at 862 × 480 and then resizing to 800 × 480, we can treat the display as if it had square pixels. To configure this panel, set REG HSIZE to 862, then issue command cmd hsf(800).
Development Support
We’re offering the ME817EV development board and 7” 1024x600 TFT LCD panel with capacitive touch screen RiTFT-70H-CAP. Display is fully compatible with ME817EV.
To simplify HMI design, Bridgetek offers EVE ScreenDesigner (ESD), but the code it generates is specific to the FT9XX series of microcontrollers, and the procedure for porting the generated code is only available for the STM32L4XX platform.
If you do not use the FT9XX as your MCU, you can use the EVE Screen Editor (ESE) instead to design individual screens and write code for the logic of moving between screens yourself.
EVE chips comparison helps you pick the right IC for your application.
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