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How to Scroll Text on a Character Display

Application Note FAN2201

In this application note, we will discuss how to scroll text on a character display using the Arduino Uno (Rev 3). A simple demonstration featuring the C164AXBSYLY6WT 16x4 character display module is provided as an example.

 

 

 

1. Introduction

With the growing popularity of easy-to-use hardware such as the Arduino1 or Raspberry Pi2, it is easier to build systems. In this application note, a simple display project is shown wherein text is horizontally scrolled. It features the C164AXBSYLY6WT character display module (datasheet):

  • 16 pins, 87.0 mm x 60.0 mm
  • 16x4 display, STN
  • ST7066U Driver IC
  • Yellow background
  • Yellow or green backlight
  • Wide temperature (-20ºC to +70ºC)
  • Positive transreflective
  • Bottom viewing angle (6 ‘O Clock)
  • ROHS-compliant

STN (Super-twisted Nematic) provides a sharper image and wider viewing angle than TN (Twisted Nematic). The cost for STN if approximately 5% higher than TN. STN is an ideal fluid for outdoor products that need to be read at various angles.

The Transflective polarizer is a mixture of Reflective and Transmissive. It provides the ability to read the LCD with or without the backlight on. It will work for all lighting conditions from dark with backlight to direct sunlight which makes it the most common choice. There is no cost difference between Transflective, Transmissive and Reflective polarization.

arduino-uno.png

 

Figure 1: Arduino UNO

 

raspberry-pi.jpg

Figure 2: Raspberry Pi

2. What You Need

 Qty

 Description

 Store

1

Arduino UNO (Rev 3) with USB Cable

Arduino

1

C164AXBSYLY6WT Character Display Module

FocusLCDs

1

Solderless Breadboard

Adafruit

1

Male-to-Male Jumper Wires (Set)

Adafruit

1

10kΩ Potentiometer (Small)

Adafruit

1

Arduino IDE

Arduino

 


3. Instructions

           3.a Download and install the Arduino IDE (Integrated Development Environment). Or you can use the cloud-based version: “Arduino Web Editor”.

           3.b Wire up the circuit as shown in the following schematic (Figure 3). It should look similar to Figure 4. Note that Arduino pins 4 to 9 are digital I/O pins. Arduino boards also have analog I/O pins. Connect the Arduino to a PC via the USB cable.

lcd-arduino-uno-schematic.png

Figure 3: LCD and Arduino UNO Schematic

The LCD is powered from the Arduino (+5V) through its USB port. LCD contrast is varied via potentiometer R1 through pin VO. Reset (RS), Enable (E), DB4 to DB7 is controlled via the sketch. While R/W is grounded (logic LOW); this means that the program is writing to the LCD register. If it is a logic HIGH, then it is reading from the LCD register. LED+ is connected to +5V for backlighting.

 

image000.jpg

 

Figure 4: Wiring of Arduino to LCD.

           3.c Open this Arduino program (AKA Sketch): Scroll-Left-Right.ino.

arduino-ide-and-sketch.png

 

Figure 5: Arduino IDE and sketch.

The programming language used in the Arduino IDE is a derivative of C and C++ programming languages. At the heart of this sketch is LiquidCrystal library which is installed by default with the IDE. It is based on the HDD44780 LCD driver and is compatible with ST7066U.

In line 32 of the sketch, the library is initialized by associating the LCD pin to the Arduino pin it is connected to like so:

 

const int rs = 8, en = 9, d4 = 7, d5 = 6, d6 = 5, d7 = 4;

LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

 

Note that only 4 bits are needed to use the LCD (DB4 to DB7).

             3.d Specify Arduino UNO is used and select the correct PC COM port. In the IDE top menu, select Tools > “Board: Arduino / Genuino UNO”. Then again, Tools > Port.

Upload and run the sketch. The LCD should have a display like in Figure 6.

   image001.jpg

Figure 6: Sketch running on the Arduino.

4. Summary

Scrolling text in the C164AXBSYLY6WT character display module is relatively easy with the use of an Arduino and the LiquidCrystal library. Other methods are available for manipulating text: These can be found in other Focus LCDs application notes.

  • Blink()
  • AutoScroll()
  • setCursor()
  • noDisplay()

Pay attention to the initialization of the LCD library, specifically the wiring of the Arduino pin with the corresponding LCD pin. Incorrect declaration of the pins may result in a malfunction. If RS is connected to 9 and EN is connected to pin 8 of the Arduino, the initialization is:

 

LiquidCrystal lcd(9, 8, 7, 6, 5, 4);

 

Note that no variables were used. Pin numbers were directly put in as arguments which eliminates 1 line of code.

Finally, select the correct Arduino board type and PC COM port (usually COM 3) for correct operation.

 

DISCLAIMER

Buyers and others who are developing systems that incorporate FocusLCDs products (collectively, “Designers”) understand and agree that Designers remain responsible for using their independent analysis, evaluation and judgment in designing their applications and that Designers have full and exclusive responsibility to assure the safety of Designers' applications and compliance of their applications (and of all FocusLCDs products used in or for Designers’ applications) with all applicable regulations, laws and other applicable requirements.

Designer represents that, with respect to their applications, Designer has all the necessary expertise to create and implement safeguards that:

(1)     anticipate dangerous consequences of failures

(2)     monitor failures and their consequences, and

(3)     lessen the likelihood of failures that might cause harm and take appropriate actions.

Designer agrees that prior to using or distributing any applications that include FocusLCDs products, Designer will thoroughly test such applications and the functionality of such FocusLCDs products as used in such applications.

 

 

1Arduino is an open-source development platform for easily building electronics projects that can electrically sense and control other objects. Arduino boards are primarily based on the Atmel AVR (8-bit) microcontroller (Example: Arduino UNO).

2The Raspberry Pi is a single-board computer. It features the Broadcom SOC (System-on-Chip) which includes a CPU and a GPU. Similar to the Arduino, it can be used for electronics projects (professional or hobbyist).