Technology

Riverdi presents technical articles which helps you fully understand the technology and possibilities of Riverdi products.

Below you can find a list of all articles.

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Best for:

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Displaying multicolor graphic

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High resolution image presentation

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Displaying animations


TFT Technology

LCD TFT (Thin Film Transistor) is simply an actively driven TN (Twisted Nematic) display. Active means that every pixel, which is the smallest optical object in the display, is driven by a separate transistor, which is put in the pixel place. Active driving allows to achieve superior parameters in comparison to passive driven LCDs. Thanks to switching directly inside the panel structure, pixels become much faster allowing smooth grayscale driving while having higher contrast and a better viewing angle. This solution has allowed to increase the number of pixels to a level which is required to achieve full color display.

The drawing on the right shows the most typical TN (Twisted Nematic) TFT structure.

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Figure 1: Structure of LCD TFT

Discover our TFT displays

It’s important to realize that every pixel consists of minimum 3 sub-pixels which generally are the same. However, each sub-pixel is covered by a different color filter. For example, a typical 7” TFT display with resolution 800 × 480 in reality has 800 x 480 x 3 = 1,152,000 sub-pixels. In addition, it is worth mentioning that every sub-pixel can be driven with 65k (16b palette), 272k(18b palette) or even 16.7M (24b palette) grayscale levels, which makes TFT LCD quite complicated in driving. Fortunately, driving is maintained by special ASIC controllers built in the TFT.

The picture on the right shows a real photo of uncovered transistors in every sub-pixel.

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Figure 2: Real photo of TFT sub-pixels with uncovered transistors

Best for:

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Portable applications 

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Wide viewing angle applications

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Low cost IPS/MVA alternative


Enhancing the viewing angle

Most industrial TFT LCD glass that is available on the market are TN (Twisted Nematic) types. TN has many advantages, the most important among them are: well-known technology which makes it very reliable, the possibility of using it in a wide temperature range and cost-effectiveness. However, TN suffers from the phenomenon called gray scale inversion. This means that the display has one viewing side in which the image colors suddenly change after exceeding the specified viewing angle. The display's contrast can be kept in a good range; however, for the human eye, the image looks improper. It may be confusing for inexperienced users because some TN displays have e.g. viewing angles of 80/80/80/80 in their datasheet and it may seem that the image looks the same from all four sides. This is not true because the viewing angle in the datasheet is determined only by the contrast measurement omitting gray scale inversion. This is why in all of Riverdi's datasheets it is always shown which angle is the viewing direction and which one relates to gray scale inversion.

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Figure 1: Example of gray scale inversion

Ask for displays with enhancing viewing angles

In most industrial applications it is not a disadvantage because displays are viewed from maximum three angles. Nevertheless, there are a few technologies on the market that overcome this TN feature. This is important especially in consumer products (like tablets and smartphones). These technologies are based on two main solutions which are MVA (Multi-domain Vertical Alignment) and IPS (In-Plane Switching).

Riverdi can offer glass based on both technologies, however, they are not very popular in industrial products because of the significantly higher price.

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Figure 2: Viewing angles example

Through research we have found a solution to enhance TN glass viewing angles and - what is more important, how to overcome gray scale inversion. Our solution allow us to achieve lower prices than MVA and IPS solutions with similar performance. We change the structure of LCD TFT by altering the top polarizer with a special film that widens viewing angles.

Picture on the right shows an example of a display with added O-film. You can see that gray scale inversion has disappeared and the viewing angles have become wider.

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Figure 3: Display from Figure 1 after O-film addition

Best for:

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Fast development

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All kind of graphic applications

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Low cost MCU projects


FT8xx – TFT controllers

Our offer includes cutting-edge and unique solutions bringing brand new quality into the global TFT display market. Riverdi offers TFT modules with an innovative TFT controller of the FT8xx family manufactured by FTDI Co. Riverdi has developed a series of TFT modules based on this chip family.
Using the FT8xx family you do not have to deal with touchscreen handling. The whole initialization and handling process is carried out by the FT8xx controller. Thanks to having installed FT8xx controller, the user can read and register information regarding touch coordinates for up to five fingers or data about performed gestures.
All video processing is handled by EVE (Embedded Video Engine). EVE combines display, touch and audio into a single chip, providing an optimized solution with high quality graphics.
A significant feature of our products is the possibility to migrate from Riverdi displays with a resistive touchscreen to the displays with a projected capacitive touchscreen (PCT) without any changes. The only action needed is to connect to a new display. The user’s application will read the data from the capacitive touchscreen just as from the previous resistive touch screen. There is also the possibility to enter the FT801 controller into extended mode to enable handling many touch points and gestures.

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Discover displays with FT8XX controller

An example showing the potential of the FT801 controller is available in the video below.

For displays with a resolution higher than 512 x 512, Riverdi implemented the EVE 2 series for TFT controllers. It is FT811 for non-touch and resistive touch panels and FT813 for projected capacitive touchscreens.

The main features of the FT81x controllers are:

  • Maximum screen resolution up to 800 × 600 pixels
  • Bitmap size up to 800 × 600 pixels
  • Fast data transfer and JPEG loading
  • SPI and QSPI (Quad SPI) communication
  • 24-bit RGB interface
  • Main memory up to 1MB
  • Extra-large ROM fonts
  • Input pin for audio, light or temperature sensor
  • Switching to portrait orientation with REG rotate CMD SETROTATE
  • CMD PLAYVIDEO playing back motion-JPEG encoded AVI videos and a NOTEAR system enabling smooth playback at SVGA resolutions
  • CMD LOADIMAGE loads PNG images in grayscale, RGB and also palette formats with transparency
  • Multiple palettes supported by 16-bit and 32-bit colors with transparency

The Riverdi displays with the FT8xx controller have a 20-pin ZIF socket with a 0.5 mm pitch. Communication with the display is held via the SPI interface by default, but the I2C is also available. Each display with the FT8xx controller has a built-in LED converter. Brightness can be controlled by the PWM signal directly from the FT8xx controller.

LCD TFT type

Controller  type

Resolution

Color depth

Control interface

Object memory

Audio Out

Audio In

Built-in LED converter

Image decode

2.83" No Touch

FT800

240×320

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

2.83" with RTP

FT800

240×320

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

2.83" with CTP

FT801

240×320

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

3.5" No Touch

FT800

320×240

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

3.5" with RTP

FT800

320×240

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

3.5" with CTP

FT801

320×240

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

4.3" No Touch

FT800

480×272

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

4.3" with RTP

FT800

480×272

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

4.3" with CTP

FT801

480×272

262k

SPI/I2C

256KB

Mono channel

No

Yes

BMP/DXT1/Software JPG

5.0" No Touch

FT812

800×480

16.7M

SPI/QSPI

1MB

Mono channel

Mono channel

Yes

BMP/DXT1/Hardware JPG

5.0" with RTP

FT812

800×480

16.7M

SPI/QSPI

1MB

Mono channel

Mono channel

Yes

BMP/DXT1/Hardware JPG

5.0" with CTP

FT813

800×480

16.7M

SPI/QSPI

1MB

Mono channel

Mono channel

Yes

BMP/DXT1/Hardware JPG

7.0" No Touch

FT812

800×480

16.7M

SPI/QSPI

1MB

Mono channel

Mono channel

Yes

BMP/DXT1/Hardware JPG

7.0" with RTP

FT812

800×480

16.7M

SPI/QSPI

1MB

Mono channel

Mono channel

Yes

BMP/DXT1/Hardware JPG

7.0" with CTP

FT813

800×480

16.7M

SPI/QSPI

1MB

Mono channel

Mono channel

Yes

BMP/DXT1/Hardware JPG

 

Best for:

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Handheld devices

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Heavy duty environment

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Military appliactions


When durability matters – test Riverdi’s super strong capacitive touch panels

Riverdi focuses on the quality and durability of products. uxTouch and all capacitive touch panels give you an opportunity to use the highest performance cover glass such as Dragontrail™ Glass or Gorilla® Glass.
Both types of glass are damage and scratch resistant and they are exceptional in comparison to conventional types of screen glass. Their superior surface quality is obtained by special hardening techniques.
Dragontrail™ Glass and Gorilla® Glass are alkali-aluminosilicate glass that are specially hardened and cured in the manufacturing process. The special glass structure and its arrangement of molecules ensures that after scratching the damage will not spread deeper.

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Dragontrail™ – what is it exactly?

Dragontrail™ is a new generation glass produced by the experienced and well known Japanese glass company Asashi Glass (AGC). It was presented for the first time in June 2011 during a CES trial. Dragontrail™ combines optimal thickness and lightness with good mechanical properties. It is a very durable and extremely scratch resistant glass. A layer of one millimeter can withstand up to 60 kilos of weight by bending before breaking. Its hardness in Vickers scale is in the range from 595 to 673 HV. The pictures below show the structure of Dragontrail™ and soda-lime glass after a scratch test.

Scratch visibility test

Regular glass                    Dragontrail

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Scratched by diamond tip (R=50um) with speed 2mm/sec.

Ask for displays with Dragontrail coverglass

What are the differences between Dragontrail™ and Gorilla® Glass?

Dragontrail™ glass and Gorilla glass have a similar material construction and the same process of production. The differences are noticeable in their mechanical characteristics. Dragontrail™ has a higher density than Gorilla glass and is more durable by means of elasticity and hardness (Table 1).

Table 1. Mechanical features – comparison

 

 

Physical Property

Units

Gorilla Glass 4

Dragontrail

Soda-lime

Average value

Density

g/cm3

2.42

2.48

2.50

Young’s Modulus

GPa

71.70

74.00

73.00

Vickers Hardness

kg/mm2

to 701

to 673

580

Source: http://bit.ly/1ObLpqH , http://bit.ly/1ObLvOV

 

 

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Durable – does not mean unattractive!

Riverdi has made efforts to make its products look pleasant, both aesthetically and professionally. The kind of glass we use has perfect trimming obtained by materials pressing techniques and fine grinding. In order to give the product its highest aesthetic valor, glass is painted to the end of its edges. Moreover, all edges are chamfered at 45 degrees (C-cut). This results in less material chipping and lowers risk of the edge damages. All these details make the screen look very aesthetic and professional.

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0.7 mm and 1.1 mm cover glass – is it enough?

Our standard capacitive touch panels use 0.7 mm Cover Glass for their 3.5” and 4.3” sizes and 1.1 mm for 7.0” size. This does not seem not very thick; nevertheless, before any judgement, it is essential to understand how the touch screen is constructed. The touchscreen is not only glass. All touch panel modules consist of a view layer of Cover Glass, LOCA and ITO Glass. As a consequence, the total thickness of the touchscreen's structure is 1.4 mm for a model with 0.7 mm cover glass and 1.8 mm for the variant with 1.1 mm glass. Such thickness of the entire module for these sizes is usually sufficient, even in more demanding applications.
However, if you still need a thicker solution, we can offer you further cover glass thickness of 1.8 mm, so in total it will be 2.5 mm. Cover Glass up to about 2 mm is the current limitation of our standard touch panels. We have also touchscreen that can work even with glass up to 6~8 mm but they are only available for customized projects.

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Dragontrail™ is a registered trademark of Asahi Glass Co., Japan.
Gorilla® Glass is a registered trademark of Corning Incorporated. Corning, N.Y. USA.

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