LCD Character Display Guide: Difference between revisions

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{{#seo:|description=LCD displays are a great way to display information to users. This guide covers the basics of text LCDs and graphic LCDs.}}
|- valign=middle
{{#seo:|keywords=LCD}}
| align=center width=300px| __TOC__
[[Category:IntroGuide]]
| [[Image:3650.jpg|400px]]
__TOC__
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<br clear="all" />
<br clear="all" />
==Introduction==
==Introduction==
[[Image:3650.jpg|link=|500px|right]]
Liquid Crystal Displays are display devices used to convey information through arrangements of pixels.  Graphic and Text LCDs are the most common types available for electronic products.  LCDs range from something as simple as the relatively simple 16-120 character displays available for small electronics to large 60+" high definition television sets.
<br clear="all">
==How it works==
[[image: lcdlayers.png|thumb|350px|link=|Reflective twisted nematic liquid crystal display.
<ol><li>Polarizing filter film with a vertical axis to polarize light as it enters.</li>
<li>Glass substrate with Indium tin oxide (ITO) electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is turned ON. Vertical ridges etched on the surface are smooth.</li>
<li>Twisted nematic liquid crystal.</li>
<li>Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.</li>
<li>Polarizing filter film with a horizontal axis to block/pass light.</li>
<li>Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light source.)</li></ol>]]
Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, and two polarizing filters which are perpendicular to one another. With no actual liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer.  The surfaces of the electrodes in contact with the liquid crystal material are treated in order to align the crystal molecules in a certain direction.


Liquid Crystal Displays are display devices used to convey information through arrangements of pixelsGraphic and Text LCDs are the most common types available for electronic productsLCDs range from something as simple as the relatively simple 16-120 character displays available for small electronics to large 60+" high definition television sets.
In a twisted nematic device (still the most common liquid crystal device), the surface alignment directions at the two electrodes are perpendicular to each other, and so the molecules arrange themselves in a twist.  When light passes through the liquid crystal molecules the rotation of the polarization changes slightly and reduces the effect so the light can pass through mostly unaffectedIf a large voltage is applied, the liquid crystal molecules become almost completely untwisted.  This causes the light to be heavily polarized again effectively making the pixel appear blackBy adjusting the voltage, the polarization can be controlled precisely allowing you to display a full range of grey-scale.


==Principles of operation==
==Text LCDs==
[[image: lcdlayers.png|thumb|350px|Reflective twisted nematic liquid crystal display.
[[image:lcd display.png|center|link=|1000px]]
1. Polarizing filter film with a vertical axis to polarize light as it enters.
2. Glass substrate with ITO electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is turned ON. Vertical ridges etched on the surface are smooth.
3. Twisted nematic liquid crystal.
4. Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.
5. Polarizing filter film with a horizontal axis to block/pass light.
6. Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light source.)]]


==Special Characters in the ASCII Standard Set==
[[image:lcd display.png|center|1000px]]


Text LCDs display full text strings set in software. Since text characters are defined from the ASCII standard library, other ASCII standard set characters and glyphs can also be sent to the text LCD.  This can be done easily by using unicode characters within your text string.  In C#, this may look something like this:
<source lang=cpp>
tLCD.WriteText(LCDFont.Dimensions_5x8, 0, 0, "Apple starts with \u0041");
</source>


The PhidgetTextLCD displays full text strings set in software. Since text characters are defined from the ASCII standard library, other ASCII standard set characters and glyphs can also be sent to the text LCD.  This can be done easily by using unicode characters within your text string.  In C#, this may look something like this:


In this example, the string \u indicates that a unicode character follows, and the unicode character 0041 (which references the hexadecimal character code 0x41) represents the capital letter A.  After the LCD converts the unicode character, the above example would cause the LCD screen to read Apple starts with A.  A chart of all ASCII standard set character codes is available in the Appendix at the end of this manual.
In this example, the string \u indicates that a unicode character follows, and the unicode character 0041 (which references the hexadecimal character code 0x41) represents the capital letter A.  After the LCD converts the unicode character, the above example would cause the LCD screen to read Apple starts with A.


<div style="background-color: #f3f3f3; border-color: #1c9edb; border-width:1px; border-style: dashed;">
== Graphic LCDs ==
<font size="3">
Graphic LCDs use the same kind of technology as text LCDs, but the pixels are in one large grid instead of being separated into individual characters. This gives the user much more control, and enables the use of lines, shapes, and custom-sized text. Take a look at the [{{SERVER}}/products.php?product_id=LCD1100 LCD1100 - LCD Phidget] for an example of a graphic LCD screen.
<source lang=cpp>
tLCD.rows[0].DisplayString = "Apple starts with \u0041";
</source>
</font>
</div>


==Custom Characters==
==Custom Characters==
[[image:Lcdpixelarrangment.png|right|300px]]
The normal characters in the TextLCD are hard-wired and inaccessible to the user. However, custom characters can be generated for the PhidgetTextLCD.  A custom character can be any arrangement of pixels within the space allotted for a single character.  Single characters are made up of pixels arranged in a grid 5 pixels wide by 8 pixels high.  Once generated, custom characters can be stored in any one of eight volatile memory locations on the PhidgetTextLCD, and can be recalled with a simple API command from software. You can create a bitmap by defining a byte array of ones and zeroes. Ones are colored in, and zeroes are empty. If you put a line break after each row, it'll be easy to edit the bitmap.  


Custom characters can also be generated for the PhidgetTextLCD.  A custom character can be any arrangement of pixels within the space allotted for a single character.  Single characters are made up of pixels arranged in a grid 5 pixels wide by 8 pixels high.  Once generated, custom characters can be stored in any one of eight volatile memory locations on the PhidgetTextLCD, and can be recalled with a simple API command from software. When custom characters are designed, a formula is used to change the pixel design into a pair of numerical values.  The first value relates to the design of the top 4 rows of the character, and the second value relates to the design of the bottom 4 rows of the character.  Unlike the unicode characters used in the Special Characters section above, the calculated number is not in hexadecimal format but is an integer value up to six characters in length.  The calculation for custom characters can be done by hand, or can be completed for you by using the form available at www.phidgets.com/documentation/customchar.html.  Done by hand, each integer value represents the sum of two to the power of each individual on-pixel’s location within that integer-value’s half of the character.  Pixels not turned on are valued at zero.  For example, a custom character happy-face with pixels 6, 8, 11 and 13 in the upper half turned on, pixels 1, 3, 6, 8, 11, 12 and 13 in the lower half turned on, and all other pixels turned off, would result in the following integer values.
In C#, this may look something like this:
 
<source lang=cpp>


[[image:Lcdcustomcharmap.png]]
Byte[] heart = [0,0,0,0,0,
0,1,0,1,0,
1,1,1,1,1,
1,1,1,1,1,
0,1,1,1,0,
0,0,1,0,0,
0,0,0,0,0,
0,0,0,0,0];


These two values are then stored in one of eight memory locations (CG-RAM 0 to 7) on the PhidgetTextLCD by using
tLCD.SetCharacterBitmap(LCDFont.Dimensions_5x8,"\x8",heart);
the Set Custom Character method in software. In C#, this may look something like this:
<div style="background-color: #f3f3f3; border-color: #1c9edb; border-width:1px; border-style: dashed;">
<font size="3">
<source lang=cpp>
tLCD.customCharacters[0].setCustomCharacter(10560, 14666)
</source>
</source>
</font>
 
</div>
 
Once stored, characters can be recalled into a text string by either using the unicode value for the location as referenced in the ASCII chart (Appendix A) or by using the String Code method from the APIExamples in C# of both methods are shown below:
Once stored, characters can be recalled into a text string by using the unicode value for the location as referenced in the [[#Character Chart|ASCII Chart]] (in this example, '''"\x8"''').  For example, in C#:
<div style="background-color: #f3f3f3; border-color: #1c9edb; border-width:1px; border-style: dashed;">
 
<font size="3">
<source lang=cpp>
tLCD.rows[0].DisplayString = "I am happy \u0008";
</source>
</font>
</div>
<div style="background-color: #f3f3f3; border-color: #1c9edb; border-width:1px; border-style: dashed;">
<font size="3">
<source lang=cpp>
<source lang=cpp>
tLCD.rows[0].DisplayString = "I am happy " + tLCD.customCharacters[0].StringCode;
tLCD.WriteText(LCDFont.Dimensions_5x8, 0, 0,"I \x8 Phidgets!");
</source>
</source>
</font>
</div>


==Connector Pin Out and Cable Coloring Scheme==
==Character Chart==
{|
The character set is JIS X 0201 with some Greek and math symbols added. It is ASCII compatible.
|
{| {{table}} border = 1
| align="center" style="background:#f0f0f0;"|'''A (Anode)'''
| align="center" style="background:#f0f0f0;"|'''Red'''
|-
| K (Cathode)||Black
|-
| VCC||Red
|-
| GND||Black
|-
| VO||Blue
|-
| RS||Blue
|-
| R/W||Blue
|-
| EN||Blue
|-
| DB0||Green
|-
| DB1||White
|-
| DB2||Green
|-
| DB3||White
|-
| DB4||Green
|-
| DB5||White
|-
| DB6||Green
|-
| DB7||White
|}
|[[image:lcdadapterview.png|right|700px]]
|}


==Supported Screen Sizes==
{| class="wikitable"
 
|+ HD44780 Character Chart
The API supports the following screen sizes:
!
{|border = 1
! ''0'' !! ''1'' !! ''2'' !! ''3'' !! ''4'' !! ''5'' !! ''6'' !! ''7'' !! ''8'' !! ''9'' !! ''A'' !! ''B'' !! ''C'' !! ''D'' !! ''E'' !! ''F''
|1x8||2x8
|- align=center
|-
!''0''
|1x16||2x16||4x16
|<big>CC0</big>||style="background: #f2f2f2;"|&nbsp;||<big>&nbsp;</big>||<big>0</big>||<big>@</big>||<big>P</big>||<big>`</big>||<big>p</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ー</big>||<big>タ</big>||<big>ミ</big>||<big>α</big>||<big><big>p</big></big>
|-
|- align=center
|2x20||4x20
!''1''
|-
|<big>CC1</big>||style="background: #f2f2f2;"|&nbsp;||<big>!</big>||<big>1</big>||<big>A</big>||<big>Q</big>||<big>a</big>||<big>q</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>。</big>||<big>ア</big>||<big>チ</big>||<big>ム</big>||<big>ä</big>||<big><big>q</big></big>
|2x24
|- align=center
|-
!''2''
|1x40||2x40||4x40
|<big>CC2</big>||style="background: #f2f2f2;"|&nbsp;||<big>"</big>||<big>2</big>||<big>B</big>||<big>R</big>||<big>b</big>||<big>r</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>「</big>||<big>イ</big>||<big>ツ</big>||<big>メ</big>||<big>β</big>||<big>θ</big>
|- align=center
!''3''
|<big>CC3</big>||style="background: #f2f2f2;"|&nbsp;||<big>#</big>||<big>3</big>||<big>C</big>||<big>S</big>||<big>c</big>||<big>s</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>」</big>||<big>ウ</big>||<big>テ</big>||<big>モ</big>||<big>ε</big>||<big>∞</big>
|- align=center
!''4''
|<big>CC4</big>||style="background: #f2f2f2;"|&nbsp;||<big>$</big>||<big>4</big>||<big>D</big>||<big>T</big>||<big>d</big>||<big>t</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>、</big>||<big>エ</big>||<big>ト</big>||<big>ヤ</big>||<big>μ</big>||<big>Ω</big>
|- align=center
!''5''
|<big>CC5</big>||style="background: #f2f2f2;"|&nbsp;||<big>%</big>||<big>5</big>||<big>E</big>||<big>U</big>||<big>e</big>||<big>u</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>・</big>||<big>オ</big>||<big>ナ</big>||<big>ユ</big>||<big>σ</big>||<big>ü</big>
|- align=center
!''6''
|<big>CC6</big>||style="background: #f2f2f2;"|&nbsp;||<big>&</big>||<big>6</big>||<big>F</big>||<big>V</big>||<big>f</big>||<big>v</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ヲ</big>||<big>カ</big>||<big>ニ</big>||<big>ヨ</big>||<big>ρ</big>||<big>Σ</big>
|- align=center
!''7''
|<big>CC7</big>||style="background: #f2f2f2;"|&nbsp;||<big>'</big>||<big>7</big>||<big>G</big>||<big>W</big>||<big>g</big>||<big>w</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ァ</big>||<big>キ</big>||<big>ヌ</big>||<big>ラ</big>||<big><big>g</big></big>||<big>π</big>
|- align=center
!''8''
|<big>CC0</big>||style="background: #f2f2f2;"|&nbsp;||<big>(</big>||<big>8</big>||<big>H</big>||<big>X</big>||<big>h</big>||<big>x</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ィ</big>||<big>ク</big>||<big>ネ</big>||<big>リ</big>||<big>√</big>||<big>x̄</big>
|- align=center
!''9''
|<big>CC1</big>||style="background: #f2f2f2;"|&nbsp;||<big>)</big>||<big>9</big>||<big>I</big>||<big>Y</big>||<big>i</big>||<big>y</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ゥ</big>||<big>ケ</big>||<big>ノ</big>||<big>ル</big>||<big>⁻¹</big>||<big><big>y</big></big>
|- align=center
!''A''
|<big>CC2</big>||style="background: #f2f2f2;"|&nbsp;||<big>*</big>||<big>:</big>||<big>J</big>||<big>Z</big>||<big>j</big>||<big>z</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ェ</big>||<big>コ</big>||<big>ハ</big>||<big>レ</big>||<big><big>j</big></big>||<big>千</big>
|- align=center
!''B''
|<big>CC3</big>||style="background: #f2f2f2;"|&nbsp;||<big>+</big>||<big>;</big>||<big>K</big>||<big>[</big>||<big>k</big>||<big>{</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ォ</big>||<big>サ</big>||<big>ヒ</big>||<big>ロ</big>||<big>ˣ</big>||<big>万</big>
|- align=center
!''C''
|<big>CC4</big>||style="background: #f2f2f2;"|&nbsp;||<big>,</big>||<big><</big>||<big>L</big>||<big>¥</big>||<big>l</big>||<big>&#124;</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ャ</big>||<big>シ</big>||<big>フ</big>||<big>ワ</big>||<big>¢</big>||<big>円</big>
|- align=center
!''D''
|<big>CC5</big>||style="background: #f2f2f2;"|&nbsp;||<big>-</big>||<big>=</big>||<big>M</big>||<big>]</big>||<big>m</big>||<big>}</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ュ</big>||<big>ス</big>||<big>ヘ</big>||<big>ン</big>||<big>Ⱡ</big>||<big>÷</big>
|- align=center
!''E''
|<big>CC6</big>||style="background: #f2f2f2;"|&nbsp;||<big>.</big>||<big>></big>||<big>N</big>||<big>^</big>||<big>n</big>||<big>→</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ョ</big>||<big>セ</big>||<big>ホ</big>||<big>゙</big>||<big>ñ</big>||style="background: #f2f2f2;"|&nbsp;
|- align=center
!''F''
|<big>CC7</big>||style="background: #f2f2f2;"|&nbsp;||<big>/</big>||<big>?</big>||<big>O</big>||<big>_</big>||<big>o</big>||<big>←</big>||style="background: #f2f2f2;"|&nbsp;||style="background: #f2f2f2;"|&nbsp;||<big>ッ</big>||<big>ソ</big>||<big>マ</big>||<big>゚</big>||<big>ö</big>||<big>█</big>
|}
|}


 
[[image:asciichart.png|link=|center]]
==Appendix - ASCII Chart==
[[image:asciichart.png]]

Latest revision as of 20:08, 26 June 2023


Introduction

3650.jpg

Liquid Crystal Displays are display devices used to convey information through arrangements of pixels. Graphic and Text LCDs are the most common types available for electronic products. LCDs range from something as simple as the relatively simple 16-120 character displays available for small electronics to large 60+" high definition television sets.

How it works

Reflective twisted nematic liquid crystal display.
  1. Polarizing filter film with a vertical axis to polarize light as it enters.
  2. Glass substrate with Indium tin oxide (ITO) electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is turned ON. Vertical ridges etched on the surface are smooth.
  3. Twisted nematic liquid crystal.
  4. Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.
  5. Polarizing filter film with a horizontal axis to block/pass light.
  6. Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light source.)

Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, and two polarizing filters which are perpendicular to one another. With no actual liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer. The surfaces of the electrodes in contact with the liquid crystal material are treated in order to align the crystal molecules in a certain direction.

In a twisted nematic device (still the most common liquid crystal device), the surface alignment directions at the two electrodes are perpendicular to each other, and so the molecules arrange themselves in a twist. When light passes through the liquid crystal molecules the rotation of the polarization changes slightly and reduces the effect so the light can pass through mostly unaffected. If a large voltage is applied, the liquid crystal molecules become almost completely untwisted. This causes the light to be heavily polarized again effectively making the pixel appear black. By adjusting the voltage, the polarization can be controlled precisely allowing you to display a full range of grey-scale.

Text LCDs

Lcd display.png


Text LCDs display full text strings set in software. Since text characters are defined from the ASCII standard library, other ASCII standard set characters and glyphs can also be sent to the text LCD. This can be done easily by using unicode characters within your text string. In C#, this may look something like this:

tLCD.WriteText(LCDFont.Dimensions_5x8, 0, 0, "Apple starts with \u0041");


In this example, the string \u indicates that a unicode character follows, and the unicode character 0041 (which references the hexadecimal character code 0x41) represents the capital letter A. After the LCD converts the unicode character, the above example would cause the LCD screen to read Apple starts with A.

Graphic LCDs

Graphic LCDs use the same kind of technology as text LCDs, but the pixels are in one large grid instead of being separated into individual characters. This gives the user much more control, and enables the use of lines, shapes, and custom-sized text. Take a look at the LCD1100 - LCD Phidget for an example of a graphic LCD screen.

Custom Characters

The normal characters in the TextLCD are hard-wired and inaccessible to the user. However, custom characters can be generated for the PhidgetTextLCD. A custom character can be any arrangement of pixels within the space allotted for a single character. Single characters are made up of pixels arranged in a grid 5 pixels wide by 8 pixels high. Once generated, custom characters can be stored in any one of eight volatile memory locations on the PhidgetTextLCD, and can be recalled with a simple API command from software. You can create a bitmap by defining a byte array of ones and zeroes. Ones are colored in, and zeroes are empty. If you put a line break after each row, it'll be easy to edit the bitmap.

In C#, this may look something like this:

Byte[] heart = 	[0,0,0,0,0,
		 0,1,0,1,0,
		 1,1,1,1,1,
		 1,1,1,1,1,
		 0,1,1,1,0,
		 0,0,1,0,0,
		 0,0,0,0,0,
		 0,0,0,0,0];

tLCD.SetCharacterBitmap(LCDFont.Dimensions_5x8,"\x8",heart);


Once stored, characters can be recalled into a text string by using the unicode value for the location as referenced in the ASCII Chart (in this example, "\x8"). For example, in C#:

tLCD.WriteText(LCDFont.Dimensions_5x8, 0, 0,"I \x8 Phidgets!");

Character Chart

The character set is JIS X 0201 with some Greek and math symbols added. It is ASCII compatible.

HD44780 Character Chart
0 1 2 3 4 5 6 7 8 9 A B C D E F
0 CC0     0 @ P ` p       α p
1 CC1   ! 1 A Q a q     ä q
2 CC2   " 2 B R b r     β θ
3 CC3   # 3 C S c s     ε
4 CC4   $ 4 D T d t     μ Ω
5 CC5   % 5 E U e u     σ ü
6 CC6   & 6 F V f v     ρ Σ
7 CC7   ' 7 G W g w     g π
8 CC0   ( 8 H X h x    
9 CC1   ) 9 I Y i y     ⁻¹ y
A CC2   * : J Z j z     j
B CC3   + ; K [ k {     ˣ
C CC4   , < L ¥ l |     ¢
D CC5   - = M ] m }     ÷
E CC6   . > N ^ n     ñ  
F CC7   / ? O _ o     ソ ö
Asciichart.png