液晶

1 History

1.1 1901: Liquid Crystals

1901: Liquid Crystals/Otto Lehmann
In 1888, Friedrich Reinitzer (1858–1927) discovered the liquid crystalline nature of cholesterol extracted from carrots (that is, two melting points and generation of colors) and published his findings at a meeting of the Vienna Chemical Society on May 3, 1888 (F. Reinitzer: Beiträge zur Kenntniss des Cholesterins, Monatshefte für Chemie (Wien) 9, 421–441 (1888)). In 1904, Otto Lehmann published his work “Flüssige Kristalle” (Liquid Crystals). In 1911, Charles Mauguin first experimented with liquid crystals confined between plates in thin layers.

In 1922, Georges Friedel described the structure and properties of liquid crystals and classified them in three types (nematics, smectics and cholesterics). In 1927, Vsevolod Frederiks devised the electrically switched light valve, called the Fréedericksz transition, the essential effect of all LCD technology. In 1936, the Marconi Wireless Telegraph company patented the first practical application of the technology, “The Liquid Crystal Light Valve”. In 1962, the first major English language publication Molecular Structure and Properties of Liquid Crystals was published by Dr. George W. Gray.

1.2 1964: DSM

1964: DSM(Dynamic Scattering Mode)/George H. Heilmeier(RCA)/USA
In 1962, Richard Williams of RCA found that liquid crystals had some interesting electro-optic characteristics and he realized an electro-optical effect by generating stripe-patterns in a thin layer of liquid crystal material by the application of a voltage. This effect is based on an electro-hydrodynamic instability forming what are now called “Williams domains” inside the liquid crystal. In 1964, George H. Heilmeier, then working at the RCA laboratories on the effect discovered by Williams achieved the switching of colors by field-induced realignment of dichroic dyes in a homeotropically oriented liquid crystal. Practical problems with this new electro-optical effect made Heilmeier continue to work on scattering effects in liquid crystals and finally the achievement of the first operational liquid-crystal display based on what he called the dynamic scattering mode (DSM). Application of a voltage to a DSM display switches the initially clear transparent liquid crystal layer into a milky turbid state. DSM displays could be operated in transmissive and in reflective mode but they required a considerable current to flow for their operation. George H. Heilmeier was inducted in the National Inventors Hall of Fame and credited with the invention of LCDs. Heilmeier’s work is an IEEE Milestone.

1.3 1970: TN

1970: TN(Twisted Nematic)/Hoffmann-LaRoche/Switzerland
On December 4, 1970, the twisted nematic field effect (TN) in liquid crystals was filed for patent by Hoffmann-LaRoche in Switzerland, (Swiss patent No. 532 261) with Wolfgang Helfrich and Martin Schadt (then working for the Central Research Laboratories) listed as inventors. Hoffmann-LaRoche licensed the invention to Swiss manufacturer Brown, Boveri & Cie, its joint venture partner at that time, which produced TN displays for wristwatches and other applications during the 1970s for the international markets including the Japanese electronics industry, which soon produced the first digital quartz wristwatches with TN-LCDs and numerous other products. James Fergason, while working with Sardari Arora and Alfred Saupe at Kent State University Liquid Crystal Institute, filed an identical patent in the United States on April 22, 1971. In 1971, the company of Fergason, ILIXCO (now LXD Incorporated), produced LCDs based on the TN-effect, which soon superseded the poor-quality DSM types due to improvements of lower operating voltages and lower power consumption.

At this time Brown, Boveri & Cie (BBC) was also working with the devices as part of a prior joint medical research agreement with Hoffmann-LaRoche. BBC demonstrated their work to a physicist from the US who was associated with James Fergason, an expert in liquid crystals at the Westinghouse Research Laboratories. Fergason was working on the TN-effect for displays, having formed ILIXCO to commercialize developments of the research being carried out in conjunction with Sardari Arora and Alfred Saupe at Kent State University’s Liquid Crystal Institute. When news of the demonstration reached Hoffmann-LaRoche, Helfrich and Schadt immediately pushed for a patent, which was filed on 4 December 1970. Their formal results were published in Applied Physics Letters on 15 February 1971. In order to demonstrate the feasibility of the new effect for displays, Schadt fabricated a 4-digit display panel in 1972. Fergason published a similar patent in the US on either 9 February 1971 or 22 April 1971. This was two months after the Swiss patent was filed and set the stage for a three-year legal confrontation that was settled out of court. In the end, all the parties received a share of what would become many millions of dollars in royalties.

However, in the USA this decision did not have any practical relevance for Roche anymore.During the interference process the economic status of Fergason’s ILIXCO had changed for the worse, and he was forced to sell his US patent, which Roche could secure in an out-ofcourt settlement. Roche now owned both TN-patents that were competing in the interference process and could therefore renounce in the US the one with the lesser legal chances.

1.4 1972: 5CB

1972: 5CB(4-Cyano-4’-pentylbiphenyl)/George Gray(University of Hull )&RRE/UK
In the late 1960s, pioneering work on liquid crystals was undertaken by the UK’s Royal Radar Establishment at Malvern, England. The team at RRE supported ongoing work by George William Gray and his team at the University of Hull who ultimately discovered the cyanobiphenyl liquid crystals, which had correct stability and temperature properties for application in LCDs.

PEBAB was subject to breakdown when exposed to water or alkalines, and required special manufacturing to avoid contamination. In 1972 a team led by George W. Gray developed a new type of cyanobiphenyls that could be mixed with PEBAB to produce less reactive materials. These additives also made the resulting liquid less viscous, thereby providing faster response times, while at the same time making them more transparent, which produced a pure-white color display.

In the 1960s various compounds were tried with little success and it became apparent that there was no stable liquid crystal available and LCDs were acquiring poor reputation for reliability. The UK had played little part in LCD development, although much UK semiconductor research had been carried out in government defence establishments and early development of LEDs (light-emitting diodes) and diode lasers had taken place in the Services Electronics Research Laboratory (SERL) at Baldock (later to be merged with RRE) and RRE Malvern. Now events took a curious turn because a politician became involved. When the Labour government was elected in March 1966 they had promised to forge a “white hot technological revolution” and the next year they established the Ministry of Technology, headed up by Tony Benn. A number of defence laboratories including SERL and RRE were subsequently placed in this Ministry. In March 1967, the Minister of State for Technology, John Stonehouse, came to Malvern. He was surprised to hear that royalties to RCA for Cathode Ray Tubes (CRT) cost the UK more than Concorde. He authorised the director of RRE, Dr (later Sir) George McFarlane to start a program on flat panel electronic displays. Surprised at this rapid decision, McFarlane set up a Working Party under one of the RRE senior scientists, Dr Cyril Hilsum, to study the field. This recommended, in December 1969, that the UK government should fund research on flat panel electronic displays with liquid crystals as their first priority. Though formal approval of the recommendation would normally have taken some months, and indeed was never granted, RRE had anticipated approval and justified its actions by the urgent need for thin, low power displays for the portable radar sets it had invented and for portable laboratory instruments such as oscilloscopes. A Display Group under Hilsum was established, and initiated both internal research and external contracts. Dr John Kirton was charged with setting up the Displays Group and, led by Hilsum, a research consortium was also established, involving RRE, SERL, Hull University and several companies. After a few years the consortium split into two, one for materials and one for devices.

Hull University, led by Professor George Gray, was chosen as the clear UK leader in the understanding of liquid-crystal chemistry. Hull’s capability was needed because no stable liquid crystal materials had been made at the time and few worked at room temperature. The research progressed slowly at first, with Hull trying many novel compositions, but all were failures. However, in 1972 it invented a completely new family of liquid crystals, the cyanobiphenyls, which showed both environmental and operational stability.

Ludwig Pohl, Rudolf Eidenschink and colleagues at Merck KGaA in Darmstadt, successfully synthesized and tested the new class of cyanophenylcyclohexanes(PCH) based on 4-pentylphenol(USP 4130502A: Liquid crystalline cyclohexane derivatives).Together with other developments in this field, this enable a profitable industrial production and the Merck Group became the leading supplier of liquid crystal substances for various types of LCDs. They quickly became the basis of almost all LCDs, and remain a major part of Merck’s business today.Later, the Merck Group bought patents from former competitors(In 1973, Merck Ltd. acquired BDH Chemicals from the Glaxo Group) and attracted senior professionals such as in 1990 George William Gray to work with Pohl’s team.

1.5 1974: E7

1974: E7/Peter Raynes(RRE)/UK
There was still the need for the material to work over a practical temperature range, and this was very difficult. The solution came from a young scientist, Dr Peter Raynes, working in the RRE Displays Group, who deduced a method of predicting the working temperature range of a complex liquid-crystal mixture. Following his theory, in 1974 he made a liquid-crystal composition called E7 which in almost all respects met the specifications put to RRE by manufacturers of watch displays. It could be said that E7 was the saviour of the liquid-crystal industry, for it was invented at the time when nobody could see a way forward for LCDs. It remained the preferred material for many years and is still used in many devices. RRE decided on a restricted licensing strategy for E7 and originally only BDH and Hoffman-La Roche could sell the compound. Rapidly BDH dominated the market, and had been taken over by the German firm Merck in 1973. By 1977 it was the largest manufacturer of liquid crystals in the world; E7 had become its largest selling product. Less than five years earlier, the company had never made a liquid-crystal material.

1.6 1983: STN

1983: STN(Super-Twisted Nematic)/Brown, Boveri & Cie (BBC)/Switzerland
A big step forward came in 1982 when RSRE scientists Dr Colin Waters (on a BDH fellowship) and Dr Peter Raynes invented a new type of liquid crystal display, the super twisted nematic (STN) LCD. This display was different to the standard LCD in one simple, but crucial manner, the normal twist angle of 90˚ was increased to 270 ˚. The switching characteristics of the display were transformed and the standard multiplex addressing schemes now worked perfectly. The changes required in the liquid crystal materials and the fabrication of the devices were minor, and STN LCDs showing large quantities of information soon became commercially available. The STN device was patented in 1982 and subsequently licenced by the MoD to the World’s manufacturers. It yielded royalties of over a hundred million pounds, the largest return for any MOD patent. STN was the preferred display in a number of applications, including the first generations of mobile phones and laptop computers, where the availability of STN displays was a key factor in the explosive growth of these now ubiquitous technologies.

In 1983, researchers at Brown, Boveri & Cie (BBC) Research Center, Switzerland, invented the super-twisted nematic (STN) structure for passive matrix-addressed LCDs. H. Amstutz et al. were listed as inventors in the corresponding patent applications filed in Switzerland on July 7, 1983, and October 28, 1983. Patents were granted in Switzerland CH 665491, Europe EP 0131216, U.S. Patent 4,634,229 and many more countries. In 1980, Brown Boveri started a 50/50 joint venture with the Dutch Philips company, called Videlec.In 1984, Philips researchers Theodorus Welzen and Adrianus de Vaan invented a video speed-drive scheme that solved the slow response time of STN-LCDs, enabling high-resolution, high-quality, and smooth-moving video images on STN-LCDs. In 1985, Philips inventors Theodorus Welzen and Adrianus de Vaan solved the problem of driving high-resolution STN-LCDs using low-voltage (CMOS-based) drive electronics, allowing the application of high-quality (high resolution and video speed) LCD panels in battery-operated portable products like notebook computers and mobile phones. In 1985, Philips acquired 100% of the Videlec AG company based in Switzerland. Afterwards, Philips moved the Videlec production lines to the Netherlands.

1.7 1988: AM TFT-LCD


1962: TFT/RCA/USA
The MOSFET (metal-oxide-semiconductor field-effect transistor) was invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959, and presented in 1960. Building on their work with MOSFETs, Paul K. Weimer at RCA developed the thin-film transistor (TFT) in 1962. It was a type of MOSFET distinct from the standard bulk MOSFET.
1968: TFT-LCD/RCA/USA
The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of RCA Laboratories in 1968. Lechner, F.J. Marlowe, E.O. Nester and J. Tults demonstrated the concept in 1968 with an 18x2 matrix dynamic scattering mode (DSM) LCD that used standard discrete MOSFETs.
1972: Active-Matrix TFT-LCD/T. Peter Brody(Westinghouse)/USA
In 1972, the concept of the active-matrix thin-film transistor (TFT) liquid-crystal display panel was prototyped in the United States by T. Peter Brody’s team at Westinghouse, in Pittsburgh, Pennsylvania. In 1973, Brody, J. A. Asars and G. D. Dixon at Westinghouse Research Laboratories demonstrated the first thin-film-transistor liquid-crystal display (TFT LCD).As of 2013, all modern high-resolution and high-quality electronic visual display devices use TFT-based active matrix displays. Brody and Fang-Chen Luo demonstrated the first flat active-matrix liquid-crystal display (AM LCD) in 1974, and then Brody coined the term “active matrix” in 1975.
1978: a-Si TFT-LCD/RSRE & Dundee University/UK
An alternative addressing possibility was to fabricate an array of transistors using a semiconductor that could be deposited over the whole display surface, but none of the semiconductors that could give such a thin film transistor (TFT) had been proven to be stable. However, the Displays Group of RSRE learned of research at Dundee University on amorphous silicon (a-Si) for photovoltaic solar cells, and, following instinct rather than science, Cyril Hilsum thought a-Si might give suitable TFTs. RSRE lacked the facilities for making the device in house and he tried to persuade Dundee to collaborate. This was no easy task as Walter Spear and Peter LeComber of Dundee were heavily involved in developing their own invention of solar cells, and felt no enthusiasm for diluting their efforts. It was LeComber, without Spear’s blessing and possibly without his knowledge, who made the original a-Si TFT and supplied the first batch to Malvern where they were fabricated into LCDs. On Christmas Eve 1978, RSRE switched LCD pixels with a-Si TFTs for the very first time. This world first breakthrough led to the use of TFT addressed LCDs in today’s TV and computer screens. Neither RSRE nor Dundee gained financially from this development because a 1962 patent already covered the TFT as a device, with a wide mention of potential semiconductors. The MoD patent experts advised that this would frustrate any attempt to patent the invention and would hinder the chance of licensing. So this discovery, which is now in use worldwide, brought no direct economic benefit to the UK, although it brought lasting credit to both Dundee and RSRE.
1984: First Commercial TFT-LCD/Citizen Watch/Japan
In 1984, Citizen Watch, introduced the Citizen Pocket TV, a 2.7-inch color LCD TV, with the first commercial TFT LCD.
1988: 14-inch, active-matrix, full-color, full-motion TFT-LCD/Sharp/Japan
In 1988, Sharp demonstrated a 14-inch, active-matrix, full-color, full-motion TFT-LCD. This led to Japan launching an LCD industry, which developed large-size LCDs, including TFT computer monitors and LCD televisions.

1.8 1992: IPS/Hitachi/Japan

In 1990, under different titles, inventors conceived electro optical effects as alternatives to twisted nematic field effect LCDs (TN- and STN- LCDs). One approach was to use interdigital electrodes on one glass substrate only to produce an electric field essentially parallel to the glass substrates. To take full advantage of the properties of this In Plane Switching (IPS) technology further work was needed. After thorough analysis, details of advantageous embodiments are filed in Germany by Guenter Baur et al. and patented in various countries( U.S. Patent 5,576,867: G. Baur, W. Fehrenbach, B. Staudacher, F. Windscheid, R. Kiefer, Liquid crystal switching elements having a parallel electric field and betao which is not 0 or 90 degrees, filed Jan 9, 1990). The Fraunhofer Institute ISE in Freiburg, where the inventors worked, assigns these patents to Merck KGaA, Darmstadt, a supplier of LC substances. In 1992, shortly thereafter, engineers at Hitachi work out various practical details of the IPS technology to interconnect the thin-film transistor array as a matrix and to avoid undesirable stray fields in between pixels.(U.S. Patent 5,598,285: K. Kondo, H. Terao, H. Abe, M. Ohta, K. Suzuki, T. Sasaki, G. Kawachi, J. Ohwada, Liquid crystal display device, filed Sep 18, 1992 and Jan 20, 1993.) Hitachi also improved the viewing angle dependence further by optimizing the shape of the electrodes (Super IPS). NEC and Hitachi become early manufacturers of active-matrix addressed LCDs based on the IPS technology. This is a milestone for implementing large-screen LCDs having acceptable visual performance for flat-panel computer monitors and television screens. In 1996, Samsung developed the optical patterning technique that enables multi-domain LCD. Multi-domain and In Plane Switching subsequently remain the dominant LCD designs through 2006. In the late 1990s, the LCD industry began shifting away from Japan, towards South Korea and Taiwan, which later shifted to China.

1.9 2007: LCD > CRT

In the fourth quarter of 2007, LCD televisions surpassed CRT TVs in worldwide sales for the first time. LCD TVs were projected to account 50% of the 200 million TVs to be shipped globally in 2006, according to Displaybank. In October 2011, Toshiba announced 2560 × 1600 pixels on a 6.1-inch (155 mm) LCD panel, suitable for use in a tablet computer, especially for Chinese character display. The 2010s also saw the wide adoption of TGP (Tracking Gate-line in Pixel), which moves the driving circuitry from the borders of the display to in between the pixels, allowing for narrow bezels. LCDs can be made transparent and flexible, but they cannot emit light without a backlight like OLED and microLED, which are other technologies that can also be made flexible and transparent.In 2016, Panasonic developed IPS LCDs with a contrast ratio of 1,000,000:1, rivaling OLEDs.

https://en.wikipedia.org/wiki/Liquid-crystal_display
https://mraths.org.uk/?page_id=576
Why it’s So Hard to Make a Homemade LCD Screen?

2 术语

显示Device，主要描述显示技术和Component，其次是Equipment。 https://www.displayfuture.com/Display/Introduction.asp Monochrome passive-matrix LCDs/Character LCD (known also as Alphanumeric)

Thin Film Transistor, flat-panel display screen in which each pixel is controlled by one to four transistors. TFTs are usually colour displays also called active-matrix (AM) LCDs.

  • AMOLED: The best quality display technology, brought to popularity by mobile phones. Active-Matrix (AM) built on OLED technology to provide with wider screen dimensions and higher matrix resolution. AMOLED displays feature high colour saturation, high contrast, high speed and amazing viewing angle.

  • OLED: This is the most popular technology of self-emission (active) displays, with brighter and clearer images (monochrome, full or scaled colour). Known also as PM (Passive-Matrix) OLED, features with high contrast and high speed. Extremely thin displays, low power consumption for high performance. Great viewing angle (>160°), wide temperature range and impressive miniaturization.

  • E-paper: Technically known as AMEPD (Active Matrix Electrophoretic Display), they are static activation displays: they hold the dot matrix activated with no power consumption. E-paper displays draw ultra-low power, providing wide viewing angles, they are perfectly sunlight readable and very thin, they also feature high density dot matrix and good contrast. Due to E-paper technology, the E-paper cannot support backlight and have slow refreshing time.

https://www.displayfuture.com/Display/Glossary.asp

  • LCD: Liquid Crystal Display. liquid crystal sits within a pair of transparent electrodes.

  • LCM: LCD Module. LCD glass with controllers or/and drivers circuit, inter-connector, possibly with BLU and connector.

  • LED: Light Emitting Diode. Source unit for BLU with minimum 50,000 life time. Broad color variety.

  • OLED: Organic LED. Emissive display technology (do not require BLU) that comprises a film of organic compounds. Wide 160’ Viewing Angle and stunning definition for both monochromatic and color display. High brightness and low power consumption.

  • TN: Twisted Nematic. The simplest and cheapest crystal technology for low duty displays. Limited viewing angle.

  • HTN: Higher Twisted Nematic. Their crystal molecules have a higher twisted angle than TN, thus provide clearer visibility and wider viewing angle.

  • STN: Super Twisted Nematic. Their crystal molecules have a higher twisted angle than HTN. For high-duty drive LCD. STN is the commonly used LCD material in passive character and graphic LCDs.

  • FSTN: Film Super Twisted Nematic. Compensation RCF (Retardation Control Film) is used to achieve black dot on white color. Usual color: (positive) dark-blue dot on light-grey or yellow/green; (negative) white dot on blue.

  • CSTN: Color STN. They employ RGB pixels. Different technology than (area) Color LCD.

  • Duty: Multiplexing index for multiplexed voltage method: used to reduce the number of ITO tracks and inter-connector lines. Duty= 1/y, means 1 lines activates y segments. Higher duty comes with less contrast quality.

  • Bias: Lowest voltage level for multiplexed voltage methods. Indicates the number of driving voltage levels: with bias=1/x, there are x+1 driving voltage levels (1, 1/2, 1/3 … 1/x times the max voltage level). Bias is correlated to Duty value.

  • Booster: Electronic device that generates all voltage levels (Bias) for the multiplexed voltage methods. Sometimes it is integrated into IC controller, sometimes requires addition of external capacitors.

  • CCFL: Cold Cathode Fluorescent Lamp. Low power and bright white light source, with life-time up to 30,000 hours. Requires light-guide and DC/AC converter.

https://www.crystalfontz.com/blog/what-is-a-display/

  • COB: Chip On Board. The ICs are on PCB. It requires a mounting media to both electrically and physically connect the PCB to the glass.

  • COF: Chip On Film. Technology on FPC for IC and other electronic components. Minimize display sizes. More robust than TAB but bigger pads/tracks pitch.

  • COG: Chip On Glass. The glass of the display is the physical support for the IC, therefore the glass surface needs to be few millimeter bigger in one axis to accommodate IC.

  • ITO: Indium Tin Oxide. It is transparent and colorless in thin conductor layers, used as signal carrier on glass for pixels activation.

3 控制器/驱动(Controller/Driver)

厂家

Mono/Char/Dot Matrix

Mono/Graphic/Dot Matrix

TFT

Graphic/OLED

https://www.sitronix.com.tw

ST7066U①, ST7032②

ST7565①, ST7567②

ST7789①, ST7735②

https://www.solomon-systech.com

SSD1963①

SSD1306①

http://www.ilitek.com

ILI9341①

HD44780①

SPLC780D①

KS0066U①

http://www.i-core.cn

AIP31066①

表1 主要参数

common

segment

extra cascaded drivers

ST7066U

16

40

ST7065/ST7063

ST7032

17

80

no need

表1 主要参数

Dot Matrix LCD Controller/Driver Instruction compatible to ST7066U and KS0066U and HD44780 Available in COG type

HD44780 Class https://learn.microsoft.com/zh-cn/dotnet/api/iot.device.characterlcd.hd44780 The Hitatchi HD44780 was released in 1987 and set the standard for LCD controllers. Hitatchi does not make this chipset anymore, but most character LCD drivers are intended to be fully compatible with this chipset. Some examples: Sunplus SPLC780D, Sitronix ST7066U, Samsung KS0066U, Aiptek AIP31066, and many more.

Some compatible chips extend the HD44780 with addtional pins and features. They are still fully compatible. The ST7036 is one example.

This implementation was drawn from numerous datasheets and libraries such as Adafruit_Python_CharLCD.

https://os.mbed.com/components/HD44780-Text-LCD/ https://os.mbed.com/users/wim/notebook/textlcd-enhanced/ Note that there are many HD44780 compatible LCD controllers around (e.g. KS0066, ST7066, SPLC780, SED1278, LC7985A, NT7603, AIP31066). There are also controllers available that are compatible and provide additional features like an increased number of segment drivers for more characters or internal LCD contrast voltage generators (e.g. KS0073, KS0078, ST7036, SSD1803, SSD1803A, HD66712, SPLC792A). Several other types of displays use controllers that are compatible with the HD44780 to allow an easy transition, for example OLED drivers such as the WS0010 and US2066 or SSD1311. The library controls the HD44780 through a 4-bit bus either directly or by using SPI or I2C portexpanders. Several compatible controllers also have native support for SPI and/or I2C serial interfaces in addition to, or instead of, the parallel bus (eg ST7032i, ST7036i, ST7070, SSD1803, AIP31068, PCF211X, AC780). The enhanced TextLCD library supports some of these devices.

Native I2C and SPI interface support (June 2014) TextLCD has been extended with support for controllers that have native I2C or SPI interfaces (eg ST7032i). Declare these as TextLCD_SPI_N() or TextLCD_I2C_N respectively.

LCDType enhancements (June 2014, Aug 2014, Sept 2014, Oct 2014) TextLCD has been extended with additional LCDTypes for 3 or 4 line displays that are supported by some controllers (PCF211X, KS0078, ST7036 and SSD1803A). These LCDTypes use different addressing schemes and are identified by a letter added to the LCDtype enumerator. TextLCD has been extended with additional controllers (US2066/SSD1311 (OLED), PT6314 VFD). Added support for blinking UDCs and Powerdown on controllers with these capabilities. Added support for AC780. Added some I2C expander module types and added support for modules that use inverted logic for backlight control.

LCDType enhancements (Nov 2014) Added ST7070 and KS0073 support, added setIcon(), clrIcon() and setInvert() method for supported controllers.

LCDType enhancements (March 2015, April 2015, May 2015) Improved speed for PCF8574 and MCP23008 I2C expander interfaces, Fixed problem in Adafruit I2C/SPI LCD portexpander. Fixed occasional init problem. Added PCF2119R and HD66712. Added some I2C portexpander types.

LCDType enhancements (Nov 2015) Added SPLC792A. Added some defines to reduce memory footprint (LCD_TWO_CTRL, LCD_CONTRAST, LCD_UTF8_FONT). Added UTF8_2_LCD() decode for Cyrilic font (By Andriy Ribalko). Added setFont() method (for SSD1803A, US2066, ST7070).

Compatible or Enhanced LCD Controllers There are many HD44780 compatible LCD controllers around (e.g. KS0066, SPLC780, SED1278, LC7985A), which will work fine with this library. There are also controllers available that are compatible while providing additional features like an increased number of segment drivers for more characters or internal LCD contrast voltage generators (e.g. KS0073, KS0078, ST7036, SSD1803A and WS0010, US2066/SSD1311 (OLED drivers)). Some of these controllers will work fine with the library without further software changes since they just remove the need for some supporting hardware that an HD44780 based display would have used. However, some new features require additional code and some displays won’t even work without these specific new set-up instructions. The library has been extended further to support some of the features provided by alternative controllers (i.e. ST7036, and WS0010 OLED driver with internal DC/DC converters). The additional software is found in the init() method and a new parameter in the constructor is needed to identify the alternative controllertype and activate the new code. Support for some controllers with native SPI or I2C interfaces is now available and will be further improved and extended. Support for setting LCD Contrast on controllers which provide that option has also been added. Some controllers (eg US2066/SSD1311, SSD1803A) also support changing display orientation. This may be used to flip between top and bottom view when the display is turned upside down. This feature is controlled through the setOrient() method. Icons and blinking features are supported as explained above. Double height lines are available on some controllers and may be selected by the setBigFont() method. However, this doesn’t look great on most displays due to the small gap between lines…

液晶显示（二）—–字符控制IC-ST7066应用
在单色LCD应用中，字符液晶模组是应用很广泛的一种显示组件。到目前为止，像16x2,20x2,24x2的字符模组还有广泛应用。前面说过，要实现LCD显示，必须搭配合适的控制驱动电路才能实现显示功能。ST7066就是一颗专为实现字符显示的控制IC。由台湾ST(矽创）推出，成为最早替代HD44780（日立）和S6A0069（三星）字符控制IC的公司之一。虽然目前有国内的AIP31066(无锡中微爱芯）、UCI7066（台湾晶宏）的替代品出现，但ST7066还是占有比较大的应用。这几家的芯片基本可以兼容替换。这里就以ST7066为例，介绍字符液晶模组的驱动方式。

先介绍几个单色LCD驱动控制常用的术语

  • VDD(VCC)—-指IC工作电压，通常2.7-5.5V；

  • VOP（VLCD）—-指能驱动LCD显示的电压，段码类和字符类一般不超过5V；点阵类最高可到24.0V；

  • DUTY—-可简单理解为显示行数的倒数，如1/16duty,实际驱动行数16行；

  • BIAS—-可简单理解为把显示电压进行分压的分压比，BIAS跟DUTY有直接关系，一般1/4DUTY–>1/3bias；1/16DUTY–    >1/5bais；1/32DUTY–>1/6bias；1/64DUTY–>1/9bias；1/128DUTY–>1/12bias；1/240DUTY–>1/16bias；

  • COM—-行驱动；

  • SEG—-列驱动；  CGROM—-内部字符只读存储器，ST7066自带240个标准西文字符，出厂时已经写人ROM内，用户不可更改；

  • CGRAM—-内部字符随机存储器，ST7066允许用户自定义8个5x点阵或者4个5x11点阵字符；

  • DDRAM—-显示数据存储器，这个存储器定义了显示数据在内存中的显示地址(与显示屏的位置对应）。ST7066满屏最大显示80个字符，第一行起始地址为0x80，结束地址0xCF（单行）；如果是2或是4行显示，则第二行的开始地址从0xC0开始；

ST7066本身带有16个COM输出，40个SEG输出，按照西文字符5x8点阵格式，则可实现1行16个字符（16x1）或者2行8个字符（8x2）；如果搭配ST7065（40列输出）或者ST7063（80列输出）驱动器，可实现显示字符扩充，最大可实现40x2个字符显示。

  • 工作电压2.7-5.5V（IC），LCD显示驱动电压3.0-18.0V（超过VDD电压时，需要外部供电）；

  • 支持4BIT/8BIT并口通讯（AIP和UC新推出的还支持SPI/IIC）；

  • 软件可选择DUTY，1/8,1/11,1/16duty；

  • 内部自带240个5x8西文字符库（CGROM），支持不同字库（英日字库ST7066-0A，英欧字库ST7066-0B等），注意ST7066系列不支持汉字显示，显示汉字库有另外的控制IC–ST7920，以后介绍；

https://www.displayfuture.com/engineering/datasheets.asp