living with the lab

using a parallax serial LCD with an Arduino

Parallax 4x20 LCD (part number 27979) with Arduino Duemilanove

LCD wiring

living with the lab

RX = wire to receive serial data from Arduino5V = power wireGND = ground wire

a servo extension is handy for wiring the LCD to the Arduino

2

Arduino wiring

living with the lab

TX = wire to transmit serial data from digital I/O pin to LCD

5V power

ground

3

LCD and Arduino together

living with the lab

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Programming

living with the lab

Text: “Louisiana Tech University” is displayed, with character locations chosen to center the text on the first two lines of the LCD

Integers: The text “i=“ is printed followed by an integer that varies from 1 to 10

Floating Point Numbers: The text “x=“ is printed followed by a number with four numerals printed to the right of the decimal; the value here ranges from 0.0010 to 0.0100

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Cursor Position & Printing to the 4x20 LCD

living with the lab

128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147

148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167

168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187

188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

0

1

2

3

Serial.write(131); // move cursor to row 0 position 3 Serial.write("Louisiana Tech"); // print “Louisiana Tech” at (0,3)

row 0, position 3

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Setting the Communication Rate

living with the lab

Serial.begin(9600);

The dip switches on the back of the LCD are set to SW1=off and SW2=on. This causes the LCD to look for data arriving at a rate of 9600 bits per second. The sketch must include . . .

. . . so that the Arduino will know to send data to the LCD at a rate of 9600 bits per second.

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A Complete Sketchliving with the lab

/*****************************************************************************//* David Hall September 2012 *//* Example program using a Parallax 4x20 LCD to output text and numbers. *//* The following screen is printed: *//* *//* --------------------- *//* | Louisiana Tech | *//* | University | *//* | | *//* | i=8 x=0.0080 | where 1<=i<=10 and 0.0000<=x<=0.0100 *//* --------------------- *//* *//* The program prints out both integers and floating point numbers. The *//* floating point number is printed to four decimal places. *//* *//* A partial listing of commands recognized by the LCD is provided below. *//* See the data sheet for the LCD on the Parallax web site for more details. *//* Serial.write(8) - move cursor one space left *//* Serial.write(9) - move cursor one space right *//* Serial.write(10) - move cursor down one line */ /* Serial.write(12) - clear screen and move cursor to top left *//* Serial.write(13) - carriage return (will wrap if on last line) *//* Serial.write(17) - turn backlight on *//* Serial.write(18) - turn backlight off *//* Serial.write(21) - turn display off *//* Serial.write(22) - turn display on, cursor off, no blink *//* Serial.write(23) - turn display on, cursor off, character blink *//* Serial.write(24) - turn display on, cursor on, no blink (default) *//* Serial.write(25) - turn display on, cursor on, character blink *//* Serial.write(128) moves the cursor to row 0 and position 0 *//* row and position commands are shown below for all 80 character positions *//* ROW 0: 128=(0,0) 129=(0,1) 130=(0,2) 131=(0,3) 132=(0,4) *//* 133=(0,5) 134=(0,6) 135=(0,7) 136=(0,8) 137=(0,9) *//* 138=(0,10) 139=(0,11) 140=(0,12) 141=(0,13) 142=(0,14) *//* 143=(0,15) 144=(0,16) 145=(0,17) 146=(0,18) 147=(0,19) *//* ROW 1: 148=(1,0) 149=(1,1) 150=(1,2) 151=(1,3) 152=(1,4) *//* 153=(1,5) 154=(1,6) 155=(1,7) 156=(1,8) 157=(1,9) *//* 158=(1,10) 159=(1,11) 160=(1,12) 161=(1,13) 162=(1,14) *//* 163=(1,15) 164=(1,16) 165=(1,17) 166=(1,18) 167=(1,19) *//* ROW 2: 168=(2,0) 169=(2,1) 170=(2,2) 171=(2,3) 172=(2,4) *//* 173=(2,5) 174=(2,6) 175=(2,7) 176=(2,8) 177=(2,9) *//* 178=(2,10) 179=(2,11) 180=(2,12) 181=(2,13) 182=(2,14) *//* 183=(2,15) 184=(2,16) 185=(2,17) 186=(2,18) 187=(2,19) *//* ROW 3: 188=(3,0) 189=(3,1) 190=(3,2) 191=(3,3) 192=(3,4) *//* 193=(3,5) 194=(3,6) 195=(3,7) 196=(3,8) 197=(3,9) *//* 198=(3,10) 199=(3,11) 200=(3,12) 201=(3,13) 202=(3,14) *//* 203=(3,15) 204=(3,16) 205=(3,17) 206=(3,18) 207=(3,19) *//* *//* To print variables to the LCD, you need to use the Serial.print() *//* command instead of the Serial.write() command. For example, the command *//* Serial.print(x,4) will send variable "x" to the LCD with four digits *//* beyond the decimal point. *//*****************************************************************************/

void setup() { Serial.begin(9600); // use a baud rate of 9600 bps pinMode(1,OUTPUT); // set pin1 as an output (pin1=TX) Serial.write(12); // clear screen & move to top left position Serial.write(131); // move cursor to row 0, position 3 Serial.write("Louisiana Tech"); // print a text string starting at (0,3) Serial.write(153); // move cursor to row 1, position 5 Serial.write("University"); // print a text string starting at (1,5) Serial.write(190); // move cursor to row 3, position 2 Serial.write("i= x="); // print text string at (3,2) Serial.write(22); // turn cursor off to keep screen clean}

void loop() { float x=0.0; for (int i=1;i<=10;i++) { x=x+0.0010; // add 0.001 to variable x Serial.write(192); // move cursor to row 3, position 4 Serial.print(i); // print i at the current cursor position Serial.write(" "); // print blanks to cover previous printing Serial.write(200); // move cursor to row 3, position 12 Serial.print(x,4); // print x to 4 decimal places delay(1000); // delay 1 second between printing numbers }}

This sketch does not require a special library (only the Serial commands commonly used in sketches)

See the Parallax website (www.parallax.com) for more details. Custom characters and other features are available for this LCD.

When developing your sketch, print things to the LCD screen only once if they do not change. For example, the text in this sketch is printed once in setup(), while the variables are printed repeatedly in loop().

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living with the lab

After downloading your sketch, you may need to press the Arduino reset button to remove “gibberish” that may be printed on the LCD.

reset button

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A Complete Sketch (for old IDE)living with the lab

/*****************************************************************************//* David Hall November 2010 *//* Example program using a Parallax 4x20 LCD to output text and numbers. *//* The following screen is printed: *//* *//* --------------------- *//* | Louisiana Tech | *//* | University | *//* | | *//* | i=8 x=0.0080 | where 1<=i<=10 and 0.0000<=x<=0.0100 *//* --------------------- *//* *//* The program prints out both integers and floating point numbers. The *//* floating point number is printed to four decimal places. *//* *//* A partial listing of commands recognized by the LCD is provided below. *//* See the data sheet for the LCD on the Parallax web site for more details. *//* Serial.print(8,BYTE) - move cursor one space left *//* Serial.print(9,BYTE) - move cursor one space right *//* Serial.print(10,BYTE) - move cursor down one line */ /* Serial.print(12,BYTE) - clear screen and move cursor to top left *//* Serial.print(13,BYTE) - carriage return (will wrap if on last line) *//* Serial.print(17,BYTE) - turn backlight on *//* Serial.print(18,BYTE) - turn backlight off *//* Serial.print(21,BYTE) - turn display off *//* Serial.print(22,BYTE) - turn display on, cursor off, no blink *//* Serial.print(23,BYTE) - turn display on, cursor off, character blink *//* Serial.print(24,BYTE) - turn display on, cursor on, no blink (default) *//* Serial.print(25,BYTE) - turn display on, cursor on, character blink *//* Serial.print(128,BYTE) moves the cursor to row 0 and position 0 *//* row and position commands are shown below for all 80 character positions *//* ROW 0: 128=(0,0) 129=(0,1) 130=(0,2) 131=(0,3) 132=(0,4) *//* 133=(0,5) 134=(0,6) 135=(0,7) 136=(0,8) 137=(0,9) *//* 138=(0,10) 139=(0,11) 140=(0,12) 141=(0,13) 142=(0,14) *//* 143=(0,15) 144=(0,16) 145=(0,17) 146=(0,18) 147=(0,19) *//* ROW 1: 148=(1,0) 149=(1,1) 150=(1,2) 151=(1,3) 152=(1,4) *//* 153=(1,5) 154=(1,6) 155=(1,7) 156=(1,8) 157=(1,9) *//* 158=(1,10) 159=(1,11) 160=(1,12) 161=(1,13) 162=(1,14) *//* 163=(1,15) 164=(1,16) 165=(1,17) 166=(1,18) 167=(1,19) *//* ROW 2: 168=(2,0) 169=(2,1) 170=(2,2) 171=(2,3) 172=(2,4) *//* 173=(2,5) 174=(2,6) 175=(2,7) 176=(2,8) 177=(2,9) *//* 178=(2,10) 179=(2,11) 180=(2,12) 181=(2,13) 182=(2,14) *//* 183=(2,15) 184=(2,16) 185=(2,17) 186=(2,18) 187=(2,19) *//* ROW 3: 188=(3,0) 189=(3,1) 190=(3,2) 191=(3,3) 192=(3,4) *//* 193=(3,5) 194=(3,6) 195=(3,7) 196=(3,8) 197=(3,9) *//* 198=(3,10) 199=(3,11) 200=(3,12) 201=(3,13) 202=(3,14) *//* 203=(3,15) 204=(3,16) 205=(3,17) 206=(3,18) 207=(3,19) *//*****************************************************************************/

void setup() { Serial.begin(9600); // use a baud rate of 9600 bps pinMode(1,OUTPUT); // set pin1 as an output (pin1=TX) Serial.print(12, BYTE); // clear screen & move to top left position Serial.print(131,BYTE); // move cursor to row 0, position 3 Serial.print("Louisiana Tech"); // print a text string starting at (0,3) Serial.print(153,BYTE); // move cursor to row 1, position 5 Serial.print("University"); // print a text string starting at (1,5) Serial.print(190,BYTE); // move cursor to row 3, position 2 Serial.print("i= x="); // print text string at (3,2) Serial.print(22,BYTE); // turn cursor off to keep screen clean}

void loop() { float x=0.0; for (int i=1;i<=10;i++) { x=x+0.0010; // add 0.001 to variable x Serial.print(192,BYTE); // move cursor to row 3, position 4 Serial.print(i); // print i at the current cursor position Serial.print(" "); // print blanks to cover previous printing Serial.print(200,BYTE); // move cursor to row 3, position 12 Serial.print(x,4); // print x to 4 decimal places delay(1000); // delay 1 second between printing numbers }}

If you haven’t downloaded the Arduino Integrated Development Environment (IDE) in a while, then try program below.

See the Parallax website (www.parallax.com) for more details. Custom characters and other features are available for this LCD.

When developing your sketch, print things to the LCD screen only once if they do not change. For example, the text in this sketch is printed once in setup(), while the variables are printed repeatedly in loop().

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