Graphic System Design Considerations (1)

Key Requirements - TFT Timing Pixel Clock - used to push pixels to display – Importance: determines how fast the display is refreshed  Vertical Blanking Time - Sync time between frames

Renesas Electronics America Inc.

Graphic System Design Considerations

Renesas Technology & Solution Portfolio

Microcontroller and Microprocessor Line-up

Wide Format LCDsIndustrial & Automotive, 130nm

 350µA/MHz, 1µA standby

44 DMIPS, True Low Power Embedded Security, ASSP

25 DMIPS, Low Power

10 DMIPS, Capacitive Touch

 Industrial & Automotive, 150nm

 190µA/MHz, 0.3µA standby

 Industrial, 90nm

 200µA/MHz, 1.6µA deep standby

 Automotive & Industrial, 90nm

 600µA/MHz, 1.5µA standby

 Automotive & Industrial, 65nm

 600µA/MHz, 1.5µA standby  Automotive, 40nm

 500µA/MHz, 35µA deep standby

 Industrial, 40nm

 200µA/MHz, 0.3µA deep standby

 Industrial, 90nm

 1mA/MHz, 100µA standby

 Industrial & Automotive, 130nm

 144µA/MHz, 0.2µA standby

‘Enabling The Smart Society’

Agenda

Introduction

Key Requirements

Key Requirements - Displays

 Most common display technology in embedded systems

 Many varieties of LCDs (color, monochrome, grayscale, etc…)

 Requires backlight

 Better contrast ratio than LCD

 Lighter than LCD

 Uses less power than LCD

 Does not emit light

 No power required to maintain color

 Commonly used on electronic readers (Amazon Kindle)

Key Requirements - Display Controllers

Timing Controller

clk, hsync, vsync, desync and data

Additional derived Sync signals

Key Requirements - Display Controllers

H Sync

V Sync

Key Requirements - TFT Timing

 Pixel Clock - used to push pixels to display

– Importance: determines how fast the display is refreshed

 Vertical Blanking Time - Sync time between frames

– Importance: visible framebuffer(s) can only be updated during vertical blanking

‘Missing‘ Data Enable Sync

for several lines marks vsync

(frame sync)

Key Requirements - Framebuffer Memory

 Example 640x480pixels w/16bpp RGB 5:6:5 color

– Double Buffered

• 640*480pixels*2 bytes/pixel * 2 buffers = 1,228,800 bytes

 Static RAM (SRAM)

– Faster but larger and more expensive– Usually internal to MCU and best used for framebuffers if available

 Dynamic RAM (DRAM)

– Must be refreshed periodically therefore slower– Usually external to MCU and best used for caching drawing objects

Key Requirements - Framebuffer Pixel Format

Key Requirements - Drawing Engine

framebuffer pixels

Drawing Engine – Textures and Warping

 Array of pixels mapped to primitive

Drawing Engine – Fast Memory Transfers

 DMA

 Accesses memory independently of the CPU

 Each row is a separate DMA instruction

 Manually skip pixels at front/end of each row

 One DMA instruction

 Many Options

– Direct Blit– Stretch Blit– Transparency– Per Pixel Alpha Blending– Color Keying

– Coloring– RLE Decompression

=>

25% Transparency

=>

Drawing Engine - Fonts

 Rendering fonts is very CPU intensive

 Each glyph has a lot of position information

 Glyphs are frequently pre-rendered

 Glyphs represented by array of pixels

 Faster to draw

 Significant memory used

 Glyphs do not scale easily

 Glyphs represented by set of curves

 Slower to draw

 Reduced memory requirement

 Glyphs scale easily

Drawing Engine – Image Compression

 Lossless compression method

 Works best with line drawings, text, or icons

 Simple algorithm (diagram below)

 JPEG

 Complex algorithms for encoding/decoding

 Lossy compression method

 Best suited for photographs

 Supports increased level of compression w/quality tradeoff

8 pixel x 4 byte = 32 byte

3

3 pixel x 4 byte + 3 cnt x 1 byte = 15 byte

System Design Discussion

System Design Discussion – Low End System

System Design Discussion – Mid Level System

System Design Discussion – High End System

System Design Example

System Example - Requirements

• Background: 24bpp RGB 6:6:6 color w/single FB

• Center: 24bpp RGB 6:6:6 color w/double FB

• Gauges: 16bpp RGB 5:6:5 color w/double FB

 Heads Up Display (HUD)

– 240 x 320 pixels (10 fps)– 1 layer

• 16bpp RGB 5:6:5 color w/single framebuffer

18bpp

60 Hz RGB Interface

System Example - Derive Timing Requirement

Example System - Derive Drawing Time

 Background: Drawn only once, so timing is not critical

Update Time ≈ X*Y*(bytes/pixel)*(1/memory rate[MB/s])*1.25 Approximation of 2.5% overhead

Update Time ≈ 2 gauges* X*Y*(1/pixel rate[MPixel/s])*1.25 Approximation of 2.5% overhead

Example System - Derive Drawing Time

 240x320 drawn from images in SDRAM (120Mb/s)

Update Time ≈ X*Y*(1/pixel rate[MPixel/s])*1.25 Approximation of 2.5% overhead

Example System - Drawing Time Summary

with the system design requirements given for memory

interface speed, screen resolution, and 2D drawing engine speed.

Example System - Derive Memory Requirement

Example System - Derive Memory Requirement

• 5 different screens are supported, so assume

5 times the framebuffer size is enough flash

Example System using a V850 DP4-H

Graphic Subsystem 120MHz

2D Drw Engine RLE Decompression Serial Flash IF

2x Video OUT 2x TCON

32-bit CPU

V850E2M Core

160 MHz

1.15 – 1.3 V (Core), 2.7- 3.6 V, 2.7 – 5.5V (I/O) -40 to +85°C, -40 to +105°C (limited spec)

Conclusion

Conclusion

Questions?

‘Enabling The Smart Society’