hitachi lcd display free sample
In this lesson, we revisit our Hitachi display so we can actually use a premade library and experience the ease with which we can now use complicated digital systems.
Hitachi compatible LCD displays are one of the most common character based displays around. This design is a sample program that shows how to drive such a display from a Hercules LaunchPad.
The display is showing a message in snake-like style. Text is snaking across the screen from the left bottom corner to the left top corner. The text on line 2 is backwards and moves towards the right. It then moves over to the top line, and moves right to left to give the impression that it is a long serpentine.
You"ll need a Hercules LaunchPad. We"ve tested on a TMS570, RM42 and RM46. You"ll need a 16x2 LCD display (TC1602, 44780, ...). I"m using one that"s mounted on a SainSmart board here, but there are many compatibles around. And you"ll need 8 wires. That"s it.
To drive the display, we"ll be using two libraries that I"ve published before for the Hercules family. The source code is available on GitHub so you have plain view on what"s happening inside. But let"s first look at the algorithm.
Scrolling through these three steps generates that snake-like scrolling effect. We"ll have to reset the pointer after we"ve dragged the full text serpentine across the display.
Here is how I translated this in code:while(1) {lcdSetCursor(0,0); // move to the beginning of the first linememcpy(sBuff, &(sBanner[uBannerLoop]), 16 );lcdPrint( sBuff);lcdSetCursor(0,1); // move to the beginning of the second linefor (uBackLoop = 0; uBackLoop < 16; uBackLoop++) {sBuff[15-uBackLoop] = sBanner[uBannerLoop+16+uBackLoop];}lcdPrint( sBuff);uBannerLoop++;if (uBannerLoop == 93) {uBannerLoop = 0;}for(uWaitCounter=0; uWaitCounter < 7000000; uWaitCounter++); //wait sometime.}
#include
// initialize the library with the numbers of the interface pinsLiquidCrystallcd(LCD_RS,LCD_E,LCD_D4,LCD_D5,LCD_D6,LCD_D7);voidsetup(){lcd.begin(16,2);// set up the LCD"s columns and rowslcd.print("How to Drive an");lcd.setCursor(0,1);lcd.print("HD44780 16x2 LCD");
The following fuctions are self-evident, taking no arguments:voidclear();voidhome();voidnoDisplay();voiddisplay();voidnoBlink();voidblink();voidnoCursor();voidcursor();voidscrollDisplayLeft();voidscrollDisplayRight();voidleftToRight();voidrightToLeft();voidautoscroll();voidnoAutoscroll();
#include
// initialize the library with the numbers of the interface pinsLiquidCrystallcd(LCD_RS,LCD_E,LCD_D4,LCD_D5,LCD_D6,LCD_D7);voidsetup(){lcd.begin(16,2);// set up the LCD"s columns and rowslcd.clear();lcd.print("Time:");lcd.setCursor(0,1);lcd.print("Time from reset.");}longcountTime=0;longoldTime=0;voidloop(){delay(1);countTime+=1;if(millis()-oldTime>99){// update every 99mslcd.setCursor(5,0);lcd.print(countTime,DEC);oldTime=millis();}
#include
// initialize the library with the numbers of the interface pinsLiquidCrystallcd(LCD_RS,LCD_E,LCD_D4,LCD_D5,LCD_D6,LCD_D7);// 0 is the full block character
// 4 has 4 left bars filled.voidcreateBarChars(void){bytemask=0x10;bytecurrent=0;for(intcgchar=1;cgchar<=4;cgchar++){current|=mask;mask=mask>>1;for(inti=0;i<8;i++)cc[i]=current;lcd.createChar(cgchar,cc);}for(inti=0;i<8;i++)cc[i]=0x1f;// Create full block.lcd.createChar(0,cc);
}voiddrawBar(bytex,bytey,bytepixels){inti;byteblocks=pixels/5;// 5 pixels wide per character.byterem=pixels%5;for(i=0;i
}longcountTime=0;longoldTime=0;voidloop(){staticintidxcg=0;delay(1);countTime+=1;if(millis()-oldTime>99){// update every 99mslcd.setCursor(5,0);lcd.print(countTime,DEC);oldTime=millis();if((countTime/250)%80==0){// Clear Bar Area.lcd.setCursor(0,1);lcd.print(" ");}drawBar(0,1,(countTime/250)%80);// parameter update is quarter seconds.}
The Hitachi HD44780 LCD controller is an alphanumeric dot matrix liquid crystal display (LCD) controller developed by Hitachi in the 1980s. The character set of the controller includes ASCII characters, Japanese Kana characters, and some symbols in two 28 character lines. Using an extension driver, the device can display up to 80 characters.
The Hitachi HD44780 LCD controller is limited to monochrome text displays and is often used in copiers, fax machines, laser printers, industrial test equipment, and networking equipment, such as routers and storage devices.
Compatible LCD screens are manufactured in several standard configurations. Common sizes are one row of eight characters (8×1), and 16×2, 20×2 and 20×4 formats. Larger custom sizes are made with 32, 40 and 80 characters and with 1, 2, 4 or 8 lines. The most commonly manufactured larger configuration is 40×4 characters, which requires two individually addressable HD44780 controllers with expansion chips as a single HD44780 chip can only address up to 80 characters.
Character LCDs use a 16 contact interface, commonly using pins or card edge connections on 0.1 inch (2.54 mm) centers. Those without backlights may have only 14 pins, omitting the two pins powering the light. This interface was designed to be easily hooked up to the Intel MCS-51 XRAM interface, using only two address pins, which allowed displaying text on LCD using simple MOVX commands, offering cost effective option for adding text display to devices.
Vee : Contrast adjustment. This is an analog input, typically connected to a potentiometer. The user must be able to control this voltage independent of all other adjustments, in order to optimise visibility of the display that varies i.a. with temperature, and, in some cases height above the sea level. With a wrong adjustment the display will seem to malfunction.
R/W : Read/Write. 0 = Write to display module, 1 = Read from display module (in most applications reading from the HD44780 makes no sense. In that case this pin can be permanently connected to ground and no processor pins need to be allocated to control it.)
Selecting 4-bit or 8-bit mode requires careful selection of commands. There are two primary considerations. First, with D3-D0 unconnected, these lines will always appear low (0b0000) to the HD44780. Second, the LCD may initially be in one of three states:
The execution times listed in this table are based on an oscillator frequency of 270 kHz. The data sheet indicates that for a resistor of 91 kΩ at VCC=5 V the oscillator can vary between 190 kHz and 350 kHz resulting in wait times of 52.6 µs and 28.6 µs instead of 37 µs. If a display with the recommended 91 kΩ resistor is powered from 3.3 volts the oscillator will run much slower. If the busy bit is not used and instructions are timed by the external circuitry, this should be taken into account.
The original HD44780 character generator ROM contains 208 characters in a 5×8 dot matrix, and 32 characters in a 5×10 dot matrix. More recent compatible chips are available with higher resolution, matched to displays with more pixels.
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