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Views: 222 Author: Tina Publish Time: 2025-04-23 Origin: Site
Content Menu
● Understanding LCD Hardware and Scrolling Basics
>> Built-in Scrolling Functions
● Software Solutions for Independent Row Scrolling
● Practical Examples and Visual Demonstrations
>> Example 1: Scrolling Only the First Row
>> Example 2: Scrolling Both Rows at Different Speeds
>> 1. Can I scroll just one row on a standard 16x2 LCD?
>> 2. Why does the built-in scroll function affect all rows?
>> 3. Is there a hardware solution for independent row scrolling?
>> 4. How can I prevent flicker when updating the display?
>> 5. Can I scroll text in different directions on each row?
Liquid Crystal Displays (LCDs) are widely used in embedded systems and DIY electronics projects for their simplicity and clarity. However, one common challenge is scrolling text on individual rows independently, especially on popular character LCDs like the 16x2 or 20x4 models. This article explores the principles, limitations, and practical solutions for achieving independent row scrolling, providing a deep dive into both hardware constraints and software workarounds. Visual aids and video resources are included to enhance understanding.
Scrolling text on an LCD is a visually engaging way to display information that exceeds the screen's width. While most LCDs support scrolling the entire display, scrolling each row independently is not natively supported by common LCD controllers. This article will walk you through the underlying reasons, demonstrate practical solutions, and provide rich visual content to help you implement independent row scrolling in your projects.
Most character LCDs, such as the 16x2 or 20x4, use the HD44780 controller or a compatible chip. These controllers organize the display as a continuous block of memory, often 80 characters long, regardless of the visible rows and columns[7].
The HD44780 controller provides commands to shift the entire display left or right, but not individual rows[7][4]. Functions like `scrollDisplayLeft()` and `scrollDisplayRight()` in the Arduino LiquidCrystal library shift all rows together[4][3].
- Unified Display Memory: The LCD controller treats the display as one continuous space, not as separate rows[7].
- No Native Command: There is no command to shift only one row; all scrolling commands affect the entire display[7][1].
- Row Mapping Complexity: The second row starts at a different address in memory, complicating direct manipulation[7].
Given the hardware constraints, independent row scrolling must be simulated in software. The key idea is to maintain a buffer for each row and update the display by writing only the visible portion of each buffer to the corresponding row[1][4][7].
- Create a buffer for each row: Store the full text you want to scroll.
- Update visible text: Periodically update the display with the substring of each buffer that fits on the screen.
- Scroll independently: Move the window for each buffer as needed to simulate independent scrolling[1][4].
Figure 2: Buffer Concept for Independent Row Scrolling
1. Initialize Buffers: Fill each row buffer with the text to display, padded with spaces as needed.
2. Set Scroll Positions: Maintain an index for each row indicating the starting character to display.
3. Update Display: At regular intervals, update each row by writing the substring starting at the current index.
4. Increment Indices: Move each index independently to scroll rows at different speeds or directions.
- Row 1: "Welcome to my blog! "
- Row 2: "Static Info"
- Row 1: Scrolls left every 300ms.
- Row 2: Scrolls right every 500ms.
- Buffer Initialization: Always pad buffers with spaces to ensure smooth scrolling off the screen[1].
- Timing Control: Use timers or delays to control the speed of each row's scroll independently.
- Display Updates: Minimize flicker by only updating the parts of the display that change.
- Memory Management: For larger displays, ensure your microcontroller has enough memory for multiple buffers.
- User Interaction: Add buttons or controls to pause, reverse, or change scroll speed dynamically.
Scrolling each LCD display row independently is not directly supported by most character LCD hardware, due to the way display memory is organized and the limitations of the controller. However, by using software buffers and updating the display with carefully managed substrings, you can achieve smooth, independent scrolling on each row. This approach is flexible, scalable to larger displays, and can be customized for a variety of creative applications.
No, standard commands will scroll the entire display. To scroll a single row, you must use a software approach with buffers for each row and update the display manually[7][1][4].
The LCD controller treats the display as a single block of memory, so any shift command applies to the entire visible area, not individual lines[7][4].
Not with common HD44780-based LCDs. Some advanced graphic LCDs or OLED displays may support more flexible addressing, but for standard character LCDs, software is the only solution[7].
Update only the changed portions of the display and avoid clearing the screen unnecessarily. Use efficient timing to balance smooth scrolling with minimal flicker[1][5].
Yes, by managing the buffer indices for each row independently, you can scroll left, right, or even pause a row while others scroll[1][4].
[1] https://forum.arduino.cc/t/seperate-rows-on-character-lcd-screen-16x2/126321
[2] https://steemit.com/utopian-io/@pakganern/iic-lcd-scrolling-text-with-arduino-tutorial
[3] https://docs.arduino.cc/learn/electronics/lcd-displays/
[4] https://www.instructables.com/Scroll-a-Single-LCD-Line-In-How-to/
[5] https://forum.arduino.cc/t/very-basic-question-about-16x2-lcd-display-scrolling/1216924
[6] https://www.youtube.com/watch?v=7SjPg9GkCJo
[7] https://electronics.stackexchange.com/questions/39700/in-lcd-display-scrolling-only-one-line
[8] https://stackoverflow.com/questions/79400876/how-to-vertically-scroll-an-lcd-display
[9] https://forums.adafruit.com/viewtopic.php?t=38982
[10] https://stackoverflow.com/questions/61249989/css-grid-layout-with-independent-scrolling-boxes
[11] https://asktimgrey.com/2023/06/09/scroll-by-row/
[12] https://www.reddit.com/r/tailwindcss/comments/r42khf/possible_to_have_3_independent_scrollable/
[13] https://stackoverflow.com/questions/14759997/scrollable-row-of-images
[14] https://forum.mikroe.com/viewtopic.php?t=67454
[15] https://www.youtube.com/watch?v=m6VLpSIyIt8
[16] https://stackoverflow.com/questions/8321849/how-to-scroll-tables-tbody-independent-of-thead
[17] https://www.youtube.com/watch?v=oWfRChp_UCI
[18] https://forums.adafruit.com/viewtopic.php?t=38620
[19] https://forums.raspberrypi.com/viewtopic.php?t=238698
[20] https://stackoverflow.com/questions/68764381/how-can-i-make-my-images-responsive-aligned-in-a-scrollable-row
