Monochrome graphic LCDs are a practical middle ground between simple character displays and full-color TFT screens. They allow pixel-level control without the complexity, cost and power consumption of color displays.
This article explains how graphic LCDs work and compares two common controller families: ST7567 and ST7920.
What Is a Graphic LCD?
A graphic LCD allows direct control of individual pixels. Unlike character LCDs, which are limited to predefined characters, graphic LCDs can display:
Custom fonts
Icons and symbols
Graphs and waveforms
Simple user interfaces
Most graphic LCDs are monochrome, meaning each pixel is either on or off.
ST7567 Graphic LCD Displays
The ST7567 is a common controller used in smaller monochrome graphic LCD modules.
Typical features:
Common resolution: 128x64 pixels
Low power consumption
SPI or parallel interface (depending on module)
Good contrast for indoor use
ST7567 displays are often used in compact embedded systems where simple graphics are needed.
Advantages of ST7567
Low power consumption
Compact size
Sufficient resolution for small interfaces
Limitations of ST7567
No color support
Limited resolution compared with TFT displays
Requires a backlight for good visibility
ST7920 Graphic LCD Displays
The ST7920 is a popular controller used in larger monochrome graphic LCD modules.
Typical features:
Common resolution: 128x64 pixels
Larger display size compared with ST7567 modules
Parallel or serial interface (often a simplified SPI-like interface)
Built-in character and graphic modes
ST7920 displays are commonly used in industrial-style interfaces and devices such as 3D printers.
Advantages of ST7920
Larger physical display size
Flexible interface options
Widely used and well supported
Limitations of ST7920
Slower updates in serial mode
Higher power consumption due to larger backlight
More complex wiring in parallel mode
ST7567 vs ST7920 Comparison
Feature
ST7567
ST7920
Typical resolution
128x64
128x64
Display size
Small
Larger
Interface
SPI or parallel
Parallel or serial
Power consumption
Low
Medium
Typical use
Compact devices
Industrial-style interfaces
Interface Options
Both ST7567 and ST7920 displays support multiple interface modes depending on the module.
SPI (or SPI-like) for reduced pin count
Parallel for higher data throughput
ST7920 displays often use a simplified serial interface that looks similar to SPI but is not fully standard.
Performance and Memory
Graphic LCDs require more memory than character displays.
For a 128x64 display:
1024 bytes are needed for a full framebuffer
Microcontrollers must update pixel data manually
Partial updates are often used to improve speed
Compared with TFT displays, monochrome graphic LCDs require much less data, which makes them easier to drive on smaller microcontrollers.
Backlight and Contrast
Graphic LCDs depend on a backlight for visibility.
Backlight brightness affects readability
Contrast is adjustable on many modules
Viewing angle is more limited than OLED
Unlike OLED displays, graphic LCDs are harder to read in low-light conditions without a backlight.
Typical Use Cases
Measurement devices
Industrial controllers
3D printer displays
Embedded user interfaces
Battery-powered devices with moderate power constraints
These displays are often chosen when graphics are needed but color is not required.
Important Practical Notes
Most modules use 5V logic, but check before connecting
Contrast adjustment is often required during setup
Libraries differ between ST7567 and ST7920
Serial modes may be slower than expected
Backlight current can be significant
Conclusion
ST7567 and ST7920 graphic LCDs provide a practical solution for monochrome graphical displays. They are more flexible than character LCDs and simpler than color TFT displays.
ST7567 is well suited for compact, low-power designs, while ST7920 is often used for larger, more visible displays in industrial-style applications. Both are reliable choices when a project needs graphics without the complexity of full-color displays.
