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| en:examples:display:lcd_alphanumeric [2010/03/05 10:52] – priitj | en:examples:display:lcd_alphanumeric [2020/07/20 09:00] (current) – external edit 127.0.0.1 |
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| ====== Alphanumeric LCD ====== | ====== Alphanumeric LCD ====== |
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| //Vajalikud teadmised: [HW] [[en:hardware:homelab:lcd]], [LIB] [[en:software:homelab:library:module:lcd_alphanumeric]], [LIB] [[en:software:homelab:library:delay]], [PRT] [[en:examples:timer:periodic_interrupt]]// | //Necessary knowledge: [LIB] [[en:software:homelab:library:module:lcd_alphanumeric]], [LIB] [[en:software:homelab:library:delay]], [PRT] [[en:examples:timer:periodic_interrupt]]// |
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| ===== Teooria ===== | ===== Theory ===== |
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| Alphanumeric LCD is liquid crystal display, which is meant for displaying letters and numbers. In simpler LCD is used liquid crystal which is put between transparent electrodes. The crystal changes the polarization of the passing light in electrical field. The electrodes are covered by polarization filters, which make sure that only one way polarized light can pass the screen. If the liquid crystal changes its polarity due to the electrical field then the light can not pass the screen or part (segment) of it and it looks dark. | Alphanumeric LCD is liquid crystal display, with the purpose of displaying letters and numbers. In basic LCD is used liquid crystal which is placed between transparent electrodes, and which changes the polarization of the passing light in electrical field. The electrodes are covered by polarization filters, which assure that only one way polarized light can pass the screen. If the liquid crystal changes its polarity due to an electrical field, the light can not pass the screen or part (segment) of it and it looks dark. |
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| Main characteristic of alphanumerical LCD is the placing of its segments. The screen is divided into many indicators. Each indicator has either enough segments for displaying letters and numbers or it is formed from matrix of little square segments (pixels). For example, a matrix of 5x7 pixels is enough to display all numbers, and letters of Latin alphabet. There are usually 1 – 4 rows of indicators and 8 – 32 columns. Each indicator has a small difference like the letters in text have | Main characteristic of alphanumerical LCD is the placing of its segments. The screen is divided into many indicators. Each indicator has either enough segments for displaying letters and numbers or it is formed from matrix of little square segments (pixels). For example, a matrix of 5x7 pixels is enough to display all numbers, and letters of Latin alphabet. There are usually 1 – 4 rows of indicators and 8 – 32 columns. Each indicator has a small difference similar to the differences of the letters in text. |
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| [{{ :examples:display:lcd_alphanumeric:lcd_alphanumeric_abc.png?200|The text formed of alphanumerical LCD pixels' matixes.}}] | [{{ :examples:display:lcd_alphanumeric:lcd_alphanumeric_abc.png?200|The text formed of alphanumerical LCD pixels' matrixes.}}] |
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| Alphanumerical LCD has besides screen, also controller which controls the segments of the screen according to the commands from the communication interface. There is a preprogrammed card of letters in the controller, where each letter, number or symbol has its own index. Displaying the text on the screen is basically done by sending the indexes to the controller. In reality there must be more control orders sent to the controller before anything can be displayed. For using LCD-s one has to introduce their data-sheets, because there are very different LCD-s. | Besides the screen Alphanumerical LCD has also controller which controls the segments of the screen according to the commands from the communication interface. A controller has a preprogrammed card of letters, where each letter, number or symbol has its own index. Displaying the text on the screen is basically done by sending the indexes to the controller. In reality there must be more control orders sent to the controller before anything can be displayed. It is important to get familiarize with each LCD data-sheet, because there are many different types of LCDs and they all are controlled differently. |
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| Alphanumerical LCD-s are usually with passive matrix, where renewal of the electrical field of the segments is tone in turns. That is why the screens with passive matrix are slower and have not so good contrast as the active matrix screens where the charge of each segment is controlled by separate transistor. There are LCD-s with reflective back and with backlight sometimes even with several different backlights. But segment colors have alphanumerical LCD-s usually still one – black usually, but there is also screens with white and colorful writings. | Alphanumerical LCDs are usually with passive matrix, where renewal of the electrical field of the segments is tone in turns. That is why the screens with passive matrix are slower and have less contrast compared with the active matrix screens where the charge of each segment is controlled by separate transistor. Some LCDs are with reflective back and others with backlight sometimes even with several different backlights. But segment colour for alphanumerical LCDs is usually still one – which is black, however there are also screens with white and colorful writings. |
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| ===== Practice ===== | ===== Practice ===== |
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| Kodulabori digitaalse mooduli külge ühendub 2x16 märgine alfabeetiline LCD WC1602A. Ekraani juhtimiseks on 4-bitine andmesiin ja 3 juhtviiku, kuid selle suhtlusprotokoll on liiga mahukas, et siinkohal lahti seletada. Lihtsuse huvides on ekraani kasutamiseks kodulabori teegis olemas vastavad funktsioonid. | HomeLabs Digital i/o module connects a 2x16 symbol alphanumerical LCD WC 1602A. For controlling the screen, there is a 4-bit data-bus and 3 control pins, but its communication protocol is too capacious, to be explained here. For simplicity, the library of the HomeLab has corresponding functions for using the display. |
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| Esimene asi, mis ekraani kasutamiseks teha tuleb, on see seadistada. Vastavaks otstarbeks on //lcd_alpha_init//-funktsioon, millega saab määrata ekraanile ka vilkuva kursori. Ekraanil on olenemata sellest, kas seda on näha või mitte, pidevalt üks aktiivne kursori positsioon, kuhu järgmine täht sisestatakse. Seega tuleb enne teksti sisestamist viia kursor soovitud asukohale. Kursori asukoha muutmiseks on //lcd_alpha_goto_xy// ja teksti kuvamiseks //lcd_alpha_write_string//-funktsioon. Kõik alfabeetilise LCD funktsioonid on lahti seletatud selle teegis. | Before using the display it is vital to adjust its settings. For this purpose is the // lcd_alpha_init// function, which sets a blinking cursor on the screen. On screen is always only one active position for the cursor where next letter is entered, regardless whether it can be seen or not. So before entering the text, the cursor must be taken to the desired place. For changing the position of the cursor is a function lcd_alpha_goto_xy and for displaying it lcd_alpha_write_string. All the functions of the alphanumerical LCD are explained in its library. |
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| | The following program code demonstrates the usage of alphanumerical LCD as a clock. The Time begins at 00:00:00 and grows approximately in every second. Since the counting of the time is done with the delay function, it is not very precise. The inaccuracy is explained in the exercise of the periodic interruption. The program counts the seconds and converts them into minutes and seconds. For using clock time is a standard function in the C-language: //sprintf//. |
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| Järgnev programmikood demonstreerib alfabeetilise LCD kasutamist kellana. Kellaaeg algab alates 00:00:00 ja suureneb iga sekundiga (ligikaudu). Kuna aja lugemine toimub viite funktsiooniga, siis pole see päris täpne. Ebatäpsust selgitab perioodilise katkestuse harjutus. Programm loeb sekundeid ja teisendab need arvutuste abil minutiteks ja sekunditeks. Kellaaja kujule viimiseks on kasutusel C-keele standardfunktsioon //sprintf//. | |
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| <code c> | <code c> |
| // | // |
| // Kodulabori alfabeetilise LCD kasutamise näide. | // The example of using the alphanumerical LCD of the HomeLab. |
| // LCD-le kuvatakse kellaaeg programmi algusest alates. | // The clock time starting at the beginning of the program is displayed on the LCD. |
| // | // |
| #include <stdio.h> | #include <stdio.h> |
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| // | // |
| // Põhiprogramm | // Main program. |
| // | // |
| int main(void) | int main(void) |
| char text[16]; | char text[16]; |
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| // LCD ekraani seadistamine | // Set-up of the LCD. |
| lcd_alpha_init(LCD_ALPHA_DISP_ON); | lcd_alpha_init(LCD_ALPHA_DISP_ON); |
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| // LCD ekraani puhastamine | // Cleaning of the LCD. |
| lcd_alpha_clear(); | lcd_alpha_clear(); |
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| // Programmi nimi | // Name of the program. |
| lcd_alpha_write_string("Aja loendur"); | lcd_alpha_write_string("The Time Counter"); |
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| // Lõputu tsükkel | // Endless loop |
| while (true) | while (true) |
| { | { |
| // Sekundite teisendamine kellaaja kujule | // Converting the seconds to the clock form: |
| // hh:mm:ss | // hh:mm:ss |
| sprintf(text, "%02d:%02d:%02d", | sprintf(text, "%02d:%02d:%02d", |
| seconds % 60); | seconds % 60); |
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| // Kellaaja teksti kuvamine LCD teise rea alguses | // Displaying the clock text in the LCD. |
| lcd_alpha_goto_xy(0, 1); | lcd_alpha_goto_xy(0, 1); |
| lcd_alpha_write_string(text); | lcd_alpha_write_string(text); |
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| // Sekundi suurendamine 1 võrra | // Growing seconds by 1. |
| seconds++; | seconds++; |
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| // Riistvaraline paus 1000 millisekundit | // Hardware delay 1000 ms. |
| hw_delay_ms(1000); | hw_delay_ms(1000); |
| } | } |
| } | } |
| </code> | </code> |
