Serial enabled LCD backpack

The Serial Enabled LCD Backpack (SerLCD) is a product made by Sparkfun that allows control of a parallel based LCD over a single-wire serial interface. The SerLCD backpack takes care of all the HD44780 commands allowing seamless integration with any digital device that can communicate via a TTL serial line. The device is designed to handle a wide range of TTL serial baud rates, and currently supports 16 or 20 character wide screens with 2 or 4 lines of display.

Serial Enabled LCD Backpack (SerLCD)
A version 2 backpack.
General Information
Manufacturer	SparkFun Electronics
Current Version	2.5
Average Price	$17
Specifications
Input Voltage	5 V
Max Input Voltage	5.5 V
Current Draw	3 mA w/o backlight 60mA w/ backlight
Clock Speed	8 MHz
Number of Positions	16
Measurements
Length	1.75 inches
Width	0.56 inches

Communication

Communication with SerLCD requires 5V TTL serial at a default baud rate of 9600bps with 8 bits of data, 1 start bit, 1 stop bit, and no parity (8-N-1). You can adjust the baud to any standard rate between 2400 and 38400bps. The power, ground and RX pins are all broken out to a 3.5mm pitch screw terminal.

Pinout

1. Ground (VSS)
2. +5V (VDD)
3. Contrast adjustment (V0)
4. High/Low Register select signal (RS)
5. High/Low Read/Write signal (R/W)
6. High/Low Enable signal (E)
7. High/Low bus line (DB0)
8. High/Low bus line (DB1)
9. High/Low bus line (DB2)
10. High/Low bus line (DB3)
11. High/Low bus line (DB4)
12. High/Low bus line (DB5)
13. High/Low bus line (DB6)
14. High/Low bus line (DB7)
15. +4.2V for LED (A)
16. Power supply for BKL 0V (K)

Features

• New PIC 16F688 utilizes onboard UART for greater communication accuracy
• Adjustable baud rates of 2400, 4800, 9600 (default), 14400, 19200 and 38400
• Operational Backspace
• Greater processing speed at 10MHz
• Incoming buffer stores up to 80 characters
• Backlight transistor can handle up to 1A
• Pulse width modulation of backlight allows direct control of backlight brightness and current consumption
• Potentiometer to control contrast
• All surface mount design allows a backpack that is half the size of the original
• Faster boot-up time
• Boot-up display can be turned on/off via firmware
• User definable splash screen

Arduino

SerLCD works seamlessly with the Arduino with the option of using the default serial transmission port, or by creating a SoftwareSerial port.

Code

//SerialLCD Functions
void selectLine(int line) {
  serCommand(); //command flag
  
  switch( line ){
    case 0:
      lcd.print(128,BYTE); //puts the cursor at line 0 char 0
      break;
    case 1:
      lcd.print(192,BYTE); //puts the cursor at line 0 char 0
      break;
    case 2:
      lcd.print(148,BYTE); //puts the cursor at line 0 char 0
      break;
    case 3:
      lcd.print(212,BYTE); //puts the cursor at line 0 char 0
      break;
    default:
      selectLine(0); //defaults back to line 0
      break;
  }
}

void goTo(int position) { //position = line 1: 0-19, line 2: 20-39, etc, 79+ defaults back to 0
  if (position<20){ Serial.print(0xFE, BYTE);   //command flag
                Serial.print((position+128), BYTE);    //position
  }else if (position<40){Serial.print(0xFE, BYTE);   //command flag
                Serial.print((position+128+64-20), BYTE);    //position 
  }else if (position<60){Serial.print(0xFE, BYTE);   //command flag
                Serial.print((position+128+20-40), BYTE);    //position
  }else if (position<80){Serial.print(0xFE, BYTE);   //command flag
                Serial.print((position+128+84-60), BYTE);    //position              
  } else { goTo(0); }
}

void clearLCD(){
   Serial.print(0xFE, BYTE);   //command flag
   Serial.print(0x01, BYTE);   //clear command.
}

void backlightOn(){  //turns on the backlight
    Serial.print(0x7C, BYTE);   //command flag for backlight stuff
    Serial.print(157, BYTE);    //light level.
}

void backlightOff(){  //turns off the backlight
    Serial.print(0x7C, BYTE);   //command flag for backlight stuff
    Serial.print(128, BYTE);     //light level for off.
}

void backlight50(){  //sets the backlight at 50% brightness
    Serial.print(0x7C, BYTE);   //command flag for backlight stuff
    Serial.print(143, BYTE);     //light level for off.
}

void serCommand(){   //a general function to call the command flag for issuing all other commands   
  Serial.print(0xFE, BYTE);
}

See also

• HD44780
• Projects containing Serial enabled LCD backpack

External links

• SparkFun SerLCD v2.5 Datasheet