Graphic LCD Modules: 128x64 to 320x240 Guide

Why Monochrome Graphic LCD Modules Still Win Design Slots

Engineers specifying a small display for an industrial product in 2025 face a crowded field: small TFT panels, OLED modules, and the long-established monochrome graphic LCD module. Yet the graphic LCD module, particularly the familiar 128x64 LCD and dot matrix LCD families, keeps winning sockets in instrumentation, medical devices, and machine controls. The reasons are practical rather than nostalgic: predictable sunlight readability, decade-long supply commitments, low power draw, and firmware that has not changed in years. This selection guide walks through resolution choices from 128x64 to 320x240, compares the ST7565, ST7920, and RA8835 controller families, and helps you decide when a monochrome LCD display is the right call versus a small TFT.

Resolution Options and What They Mean in Practice

Resolution on a monochrome graphic display is not just a pixel count—it determines character capacity, graphic detail, and how much code space your font and icon library will consume. The common industry sizes cluster around a few standards.

The Common Graphic LCD Resolutions

128x64: The workhorse. Typically shows 4 lines of 16 characters (5x8 font) or 8 lines of 21 characters with a smaller font. Ideal for menu-driven instruments, thermostats, and handheld meters.
128x128: A square format that suits gauges, dials, and simple icons. Often used in wearable-adjacent industrial tools and portable medical devices.
160x128: A wider canvas for status bars, multi-column readouts, and waveform previews. Common in bench instruments and battery-powered analyzers.
240x128: Near half-VGA width. Enough for graphing, multi-parameter displays, and denser UI layouts without moving to color.
320x240 (QVGA): The upper end of monochrome graphic modules. Supports detailed charts, kanji/CJK fonts, and bitmap graphics. Frequently specified for medical monitors and industrial HMIs.

Resolution vs Visible Quality

More pixels do not automatically mean a better-looking display. On a monochrome LCD, visible quality depends on the ratio of active pixel area to the gap between pixels (the aperture ratio), the glass mode, and the backlight uniformity. A well-made 128x64 dot matrix LCD with tight pixel pitch can look crisper than a poorly produced 240x128 panel. When comparing samples, evaluate:

Pixel fill and contrast: Look for even dot definition, not just resolution.
Viewing angle symmetry: Check both horizontal and vertical off-axis behavior.
Backlight evenness: Hotspots and dim corners are common quality escapes on larger monochrome panels.

Controller Families Compared: ST7565, ST7920, RA8835

The controller is the interface between your MCU and the glass. It dictates command set, RAM organization, font handling, and how much firmware you must write. Three families dominate the monochrome graphic LCD market.

ST7565 LCD: The Flexible Segment-and-Graphic Workhorse

The ST7565 (and its close relatives) is a column/row driver with built-in display RAM, typically used on 128x64 and similar small panels. Key traits:

SPI or parallel interface: Usually 4-wire SPI or 8-bit parallel. SPI keeps pin count low for compact designs.
No built-in font ROM: You supply fonts and graphics in MCU flash. This is flexible but increases firmware effort.
Low power: Well suited to battery-powered and low-temperature applications.
Wide availability: Many 128x64 LCD modules ship with ST7565-compatible controllers, making second-sourcing easier.

Choose ST7565 when you want a lean BOM, a small MCU footprint, and full control over the character set.

ST7920 LCD: The Character-and-Graphic Hybrid

The ST7920 is popular on 128x64 modules that need both text and graphics. Its distinguishing feature is a built-in Chinese and ASCII font ROM, plus a graphics RAM mode. Key traits:

Parallel or serial interface: 8-bit parallel is common; serial variants exist.
Built-in font ROM: Reduces MCU flash pressure and speeds up text-heavy UIs, especially for CJK markets.
Dual mode: Operates in text mode (character addressing) or graphic mode (pixel addressing).
Trade-off: The font ROM is fixed; custom fonts require graphic mode and more RAM writes.

The ST7920 LCD is a strong fit for point-of-sale terminals, medical consoles, and any product shipping to Asia where CJK text support matters.

RA8835 LCD: The Larger-Panel Controller

The RA8835 (and compatible S1D13700-class devices) targets larger monochrome panels such as 240x128 and 320x240. Key traits:

Built-in character generator: Supports text layers with hardware scrolling and layering.
Larger display RAM: Handles bigger canvases and multiple graphic layers.
More complex initialization: Requires careful timing and register setup; datasheets are essential reading.
Better for dense UIs: Ideal when you need text windows, graphs, and status areas on one screen.

The RA8835 LCD family is the choice when your 320x240 monochrome design needs layered text and graphics without offloading everything to the MCU.

Quick Comparison

Controller	Typical Resolutions	Interface	Built-in Font	Best For
ST7565	128x64, 128x128	SPI / 8-bit parallel	No	Compact, low-power, custom UI
ST7920	128x64	8-bit parallel / serial	Yes (ASCII + CJK)	Text-heavy, multilingual
RA8835	240x128, 320x240	8-bit parallel	Yes	Dense, layered graphics

Glass Modes: STN vs FSTN, Reflective vs Transflective vs Transmissive

The glass mode determines how the display behaves under different lighting—often more important than resolution for field reliability.

STN (Super Twisted Nematic): Lower cost, but narrower viewing angle and slower response. Acceptable for static or slow-updating readouts.
FSTN (Film-compensated STN): Improved contrast and wider viewing angle. The default choice for most industrial graphic LCD modules.
Reflective: No backlight; relies on ambient light. Excellent for outdoor, ultra-low-power devices but unreadable in darkness.
Transflective: Combines reflective and transmissive modes. Readable in sunlight and with backlight. The most versatile choice for handheld and outdoor equipment.
Transmissive: Backlight-dependent; best for indoor, dim environments. Common in benchtop instruments.

For most industrial products, FSTN transflective with a white or green LED backlight is the safe default. Specify reflective only when power budget is extreme and ambient light is guaranteed.

Interfaces: SPI vs 8-bit Parallel and the Cable-Length Trade-off

Interface choice affects pin count, firmware complexity, and noise immunity.

SPI: Fewer pins (typically 4-5), simpler PCB routing, and better for compact designs. However, update rate is limited, and long cables can degrade signal integrity. Best for short traces on the same board.
8-bit parallel: Faster refresh and more robust over longer cables, but consumes more MCU pins and PCB area. Preferred when the display is panel-mounted and connected via a ribbon cable.

A practical rule: use SPI when the display sits on the main board and updates are infrequent. Use parallel when the display is remote, the UI is animation-heavy, or EMI is a concern.

Backlight and Contrast Design for Outdoor and Low-Temperature Use

Monochrome LCDs shine in harsh environments, but only if backlight and contrast are designed correctly.

LED backlight: Prefer white or green LEDs with a constant-current driver. Avoid simple resistor limiting if brightness consistency matters.
Temperature compensation: STN and FSTN contrast varies with temperature. Many controllers support software contrast adjustment; some modules include thermistors or compensation circuits.
Low-temperature operation: Standard STN panels may struggle below -20°C. Specify extended-temperature glass and heaters for cold-chain, outdoor, or automotive-adjacent products.
Sunlight readability: Transflective FSTN with a high-contrast polarizer remains readable in direct sun—an advantage monochrome retains over many small TFTs.

Mechanical Integration: Size, Zebra Connector, and FPC Bend Radius

Mechanical details cause more late-stage redesigns than electrical ones.

Module outline and viewing area: Confirm both, plus the active area offset, against your enclosure CAD.
Zebra connector vs FPC: Zebra (elastomeric) connectors suit glass-on-board designs with compression frames. FPC tail connections offer more flexibility for panel mounting but require careful bend-radius planning.
FPC bend radius: Specify a generous bend radius and strain relief; repeated flexing is a common field failure.
Mounting and bezel: Account for bezel overlap, gasket compression, and tolerance stack-up early.

Graphic LCD vs Small TFT: How to Choose

This is the decision that shapes cost, power, and firmware for years. Neither technology is universally better.

Choose a monochrome graphic LCD module when:

Sunlight readability and transflective operation are required.
Power budget is tight (battery or loop-powered devices).
The product lifecycle is long and you need stable, multi-source supply.
The UI is text, icons, and simple graphs.
Operating temperature extremes favor STN/FSTN glass.

Choose a small TFT when:

Color coding, photographic images, or rich UI are essential.
The product is indoor and power is not constrained.
You need higher pixel density in a small footprint.
Touch integration is required.

Be honest about trade-offs: TFTs offer color and density but often cost more in power, require backlight and timing tuning, and can face shorter supply longevity for niche sizes. Monochrome graphic LCDs trade color for ruggedness, simplicity, and supply stability.

Resolution options at a glance

Resolution	Typical size	Controller options	Interface	Typical use
128x64	1.8–3.2”	ST7565	SPI, 8-bit parallel	Handheld instruments
128x128	2.4–3.5”	ST7565	SPI	Compact panels
160x128	2.8–3.5”	ST7565	SPI	Meters, controllers
240x128	3.5–5.7”	ST7920, RA8835	SPI, parallel	Industrial HMI
320x240	5.7–5.9”	RA8835	parallel	Legacy equipment refresh

Options referenced above are available as graphic LCD modules and TFT LCD displays; for application context see instrument and test equipment displays.

Specification Checklist and Sample Request

Before requesting samples, assemble a specification sheet covering:

Resolution and active area dimensions.
Controller family (ST7565, ST7920, RA8835, or equivalent).
Glass mode (STN/FSTN, reflective/transflective/transmissive).
Interface (SPI, 8-bit parallel, pinout).
Backlight type, color, and current.
Operating and storage temperature range.
Viewing direction and contrast requirements.
Mechanical outline, connector type, and FPC details.
Firmware support: font ROM, command set, sample code.
Qualification needs: industrial, medical (ISO 13485 supply chain), or automotive-adjacent.

When requesting samples, include your target enclosure drawing, interface preference, and environmental conditions. Suppliers who ask about your firmware stack and lifetime volume early are usually the ones worth shortlisting.

Ready to move from specification to sample? Our engineering team can help you match resolution, controller, and glass mode to your application.

Looking for a reliable LCD module supplier for your next project? Contact Relialink today to discuss your custom graphic LCD module requirements, from 128x64 LCD samples to 320x240 production programs.

Graphic LCD Modules: 128x64 to 320x240 Selection Guide