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Parallax Serial LCD
2 rows x 16 characters, Non-backlit, with Piezospeaker (#27976)
2 rows x 16 characters, Backlit, with Piezospeaker (#27977)
4 rows x 20 characters, Backlit, with Piezospeaker (#27979)
The Parallax Serial LCDs are very functional, low-cost liquid crystal displays that can be easily interfaced
to and controlled by a microcontroller using a I/O pin. The LCD displays provide basic text wrapping so
that your text looks correct on the display. Full control over all of their advanced LCD features allows you
to move the cursor anywhere on the display with a single instruction and turn the display on and off in
any configuration. They support visible ASCII characters Dec 32-127, and in addition you may define up
to eight of your own custom characters to display anywhere on the LCD.
NOTE: If your Serial LCD Display does not have a speaker on the back, use the specifications
and information in the Product Change Notice: Revision E and Earlier section on page 11.
Features
Clear 40-pixel characters (8 H x 5 W)
Supports ASCII DEC characters 32-127
Define up to eight custom characters
Automatic text wrapping
Single command cursor placement
Single command clears the display
Define up to eight custom characters
Select 2400, 9600, or 19,200 baud with switches on
the back of the device
Display type: STN, YG, positive transflective LCD
Adjustable contrast knob on the back of the device
YG LED for backlit model displays
Key Specifications
Power requirements:
o Non-backlit: +5 VDC, 20 mA
o Backlit: +5 VDC, 20 mA (light off), ~ 80 mA typical (light on)
Communication: Selectable asynchronous serial baud rates: 2400, 9600, 19200
Operating temperature: -4 to +158 F (-20 to +70C)
Dimensions: NOTE - Board and LCD size and style may vary
o 2x16: Approx. 1.42 x 3.15 in (36 x 80 mm)
o 4x20: Approx. 2.37 x 3.86 in (60.2 x 98.1 mm)
Copyright Parallax Inc. Parallax Serial LCDs (#27976, 27977, 27979) v3.1 3/11/2013 Page 1 of 11 Quick-Start Circuit
The Serial LCDs should be powered from an external regulated 5 V power supply. Make sure the power
supply has an adequate current rating to power the Serial LCD and the BASIC Stamp, Propeller chip, or
whichever microcontroller and other devices you are using.
CAUTION
DO NOT PROVIDE A SIGNAL TO THE 'RX' PIN BEFORE APPLYING 5 VDC TO THE '5V' PIN.
Baud Rate Setup
After connecting the Serial LCD, you will need to select the baud rate at which you are going to send it
data. You have three choices: 2400, 9600, and 19,200 baud. To set the baud rate, move the dip switches
on the back of the LCD into the correct positions according to the table next to the switches, which is also
repeated below:
MODE SW1 SW2
Test OFF OFF
2,400 ON OFF
9,600 OFF ON
19,200 ON ON
As you can see from the table, there is also a fourth choice called Test. Use this Test mode to confirm
that the power and ground to the LCD are hooked up correctly before you send it any data. Move the dip
switches to the Test setting and turn on the power. The LCD display should turn on with the backlight on
(models 27977, 27979) and display the following text:
Parallax, Inc.
www.parallax.com
If you dont see the text at first, try adjusting the LCD contrast by turning the pot labeled Increase
Contrast with a screwdriver. Turn it in the direction of the arrow to make the characters show up more
clearly. If you still dont see the characters, go back and check your electrical connections and try again.
Once youve successfully completed test mode, move the dip switches to the correct positions to select
the baud rate you want to use for your application.
Copyright Parallax Inc. Parallax Serial LCDs (#27976, 27977, 27979) v3.1 3/11/2013 Page 2 of 11