BT816Q-R datasheet(22/64 Pages) BRIDGETEK

22 / 64 page

BT81X (815/6) Advanced Embedded Video Engine Datasheet

Version 1.0

Document No.: BRT_000220 Clearance No.: BRT#126



In-built animated functionalities such as displaying logo, calibration, spinner, screen saver and

sketch



Snapshot feature to capture the current graphics display

For

complete

list

graphics

engine

display

commands

and

widgets

refer

BT81X_Series_Programming_Guide, Chapter 4.

4.3.2

ASTC

ASTC stands for Adaptive Scalable Texture Compression, an open standard developed by ARM for use in

mobile GPUs.

ASTC is a block-based lossy compression format. The compressed image is divided into a number of

blocks of uniform size, which makes it possible to quickly determine which block a given texel resides in.

Each block has a fixed memory footprint of 128 bits, but these bits can represent varying numbers of

texels (the block footprint).

Block footprint sizes are not confined to powers-of-two, and are also not confined to be square. For 2D

formats the block dimensions range from 4 to 12 texels.

Using ASTC for the large ROM fonts can save considerable space. Encoding the four largest fonts in ASTC

8x8 formats gives no noticeable loss in quality and reduces the ROM size from 1 MByte to about 640

Kbytes.

4.3.3

ROM and RAM Fonts

The BT815/6 has built in ROM character bitmaps as font metrics. The graphics engine can use these

metrics when drawing text fonts. There are a total of 19 ROM fonts, numbered with font handle 16-34.

Fonts 31-34 are large ROM fonts encoded in ASTC 8x8 format. The user can define and load customized

font metrics into RAM_G or external flash, making it possible to support a full range of Unicode characters

with UTF-8 coding points.

Each ROM font metric block has a 148 byte font table which defines the parameters of the font and the

pointer of font image. The font table format is shown in Table 4-7.

Address Offset

Size(byte)

Parameter Description

128

width of each font character, in pixels

128

font bitmap format, for example L1, L4 or L8

132

font line stride, in bytes

136

font width, in pixels

140

font height, in pixels

144

pointer to font image data in memory

Table 4-7 Font Table Format

The ROM fonts are stored in the memory space ROM_FONT. The ROM font table is also stored in the

ROM. The starting address of the ROM font table for font index 16 is stored at ROM_FONT_ADDR, with

other font tables following. The ROM font table and individual character width (in pixel) are listed in Table

4-8, Table 4-9 and Table 4-10. Font index 16, 18 and 20-31 are for basic ASCII characters (code 0-127),

while font index 17 and 19 are for Extended ASCII characters (code 128-255). The character width for

font index 16 through 19 is fixed at 8 pixels for any of the ASCII characters.

Font Index

Font format

Line stride

Font width

(max)

Font height

BT816Q-R Scheda tecnica(PDF) 22 Page - Bridgetek Pte Ltd.

BT816Q-R Scheda tecnica(HTML) 22 Page - Bridgetek Pte Ltd.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

Scheda tecnica Scarica

Link URL