Understanding the Most Common TFT Interfaces Used with STM32 MCUs

TFT displays are a fundamental part of modern embedded systems, from compact wearable devices and consumer products to industrial control panels and smart home interfaces. STM32 microcontrollers remain one of the most popular MCU families for driving TFT LCDs due to their performance range, abundant peripherals, and flexible interface support.

However, STM32 chips come in many variants, and not all support the same display interfaces. Choosing the correct TFT interface is crucial for achieving smooth UI performance, predictable refresh rates, and an efficient hardware design.

This article provides a clear overview of the most commonly used TFT interfaces on STM32 MCUs—SPI, 8080/6800 parallel, RGB (LTDC), and MIPI DSI—along with their strengths, limitations, and best-fit applications.

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Why TFT Interface Selection Matters for STM32 Designs

A TFT display interface determines:

• The achievable frame rate
• Maximum display resolution
• How smooth the UI feels
• How much RAM the system needs
• PCB complexity and connector size
• System cost and power consumption

Even the best TFT display will perform poorly if paired with the wrong interface. For example, an SPI connection may be fine for a small wearable screen but will be unusable for a 480×272 HMI. Conversely, using an LTDC interface for a tiny 1.3-inch display is unnecessary overhead.

Selecting the correct interface ensures the UI behaves as expected and the overall system remains stable and cost-effective.

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1. SPI Interface (3-wire / 4-wire SPI)

SPI is the simplest and most commonly used TFT interface with STM32 MCUs. It is widely supported across STM32 families, including F0, G0, F1, L0, and others.

How SPI TFT Works

The MCU sends pixel data serially. Most SPI TFT displays include an onboard controller such as:

• ST7735
• ST7789
• ILI9341
• GC9A01 (round displays)

These controllers manage GRAM (framebuffer) internally, so the MCU only sends update regions, not full frames.

Advantages

• Very low pin count (4–6 pins)
• Works on nearly all STM32 models
• Simple PCB design
• Low cost
• Good for small UIs

Limitations

• Limited bandwidth due to serial transfer
• Not suitable for high-resolution full-screen updates
• UI animations may appear slow without heavy optimization

Best Use Cases

• Wearable devices
• Tiny HMIs
• Round displays
• Sensor interfaces
• Small UI with partial refresh
• Battery-powered devices

Ideal for ≤ 240×240 resolution.

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2. 8080/6800 Parallel Interface (8-bit / 16-bit, with FSMC/FMC)

Many mid- to high-performance STM32 MCUs include the FSMC or FMC peripheral, enabling fast parallel communication with TFT controllers.

How the Parallel TFT Interface Works

Pixel data is sent over 8 or 16 data lines, plus control lines such as WR, RD, and CS. Many displays with controllers like ILI9488, HX8347, or RA8875 support this bus.

Advantages

• Much faster than SPI
• Supports 480×272 and 800×480 displays smoothly
• Good for medium-sized HMIs
• Works well with UI libraries (LVGL, TouchGFX)

Limitations

• High pin count (20–30 pins)
• Requires more PCB space
• Not available on low-end STM32 MCUs
• Ribbon cable length must be short to avoid noise

Best Use Cases

• Smart appliances
• Industrial instruments
• 3.5" to 7" HMIs
• Medium-resolution displays (320×240 – 800×480)

Most commonly used in STM32F407, F429, F767, H743 designs.

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3. RGB Interface (Driven by LTDC Peripheral)

The LTDC (LCD-TFT Display Controller) found in STM32F429+, F7, and H7 enables direct driving of TFT panels with RGB pixel data—similar to how video interfaces operate.

How RGB TFT Works

The LTDC sends continuous pixel streams over:

• 16-bit / 18-bit / 24-bit RGB lines
• Sync signals (HSYNC, VSYNC)
• Pixel Clock

The panel itself typically has no internal display controller.

Advantages

• High bandwidth
• Excellent for 480×272 up to 1280×800
• Smooth animations and responsive UI
• Works well with TouchGFX or LVGL

Limitations

• Requires an external framebuffer (SDRAM)
• High pin count
• More challenging PCB layout
• Higher power consumption
• Not supported by low-end STM32

Best Use Cases

• Medical devices
• Industrial HMI
• Automotive dashboards
• Smart home control panels
• Large or high-resolution screens
• 4.3", 5", 7", 10.1" TFT panels

Suitable when you need video-grade UI performance.

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4. MIPI DSI Interface (High-Speed Serial)

MIPI DSI is the modern interface used by smartphones. Only a few advanced STM32 MCUs support it, such as:

• STM32H7A3
• STM32H7B3
• STM32H7B0

Advantages

• Very high bandwidth
• Uses very few pins
• Supports high-resolution panels (720p and beyond)
• Enables slim device designs

Limitations

• Available only on select STM32 models
• Complex initialization
• High-speed PCB design required
• Display panels require careful matching of DSI timings

Best Use Cases

• High-end UI products
• Smart home hubs
• Portable industrial displays
• Mobile-grade screens
• Compact designs needing high resolution

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5. Comparison Summary

Interface	Max Usable Resolution	Bandwidth	Pin Count	STM32 Support	Typical Use Case
SPI	≤240×240	Low	Very low	All STM32	Wearables, small screens
8080/6800 (FSMC/FMC)	480×272 – 800×480	Medium	High	F4 / F7 / H7	Medium-size HMIs
RGB (LTDC)	480×272 – 1280×800	High	Very high	F429+ / F7 / H7	Industrial / Medical HMI
MIPI DSI	720p+	Very high	Very low	Select H7 MCUs	High-end modern UI

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6. How to Choose the Right TFT Interface for Your STM32 Project

Choose SPI if:

• Your device is small
• UI updates are simple
• You want low power and low cost

Choose 8080/6800 Parallel if:

• You want a responsive medium-size HMI
• Your MCU supports FSMC/FMC
• Screen size is between 2.8" and 7"

Choose RGB (LTDC) if:

• You need fluid UI animations
• You require 480×272 and above
• You can add external SDRAM

Choose MIPI DSI if:

• You need a smartphone-class display
• Space is limited
• Your MCU is an H7 with DSI peripheral

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Conclusion

STM32 microcontrollers provide versatile options for driving TFT displays of all sizes and performance levels. From simple SPI screens for compact devices to high-end RGB and MIPI-DSI panels for advanced HMIs, the STM32 ecosystem can support nearly any product requirement.

Selecting the right interface early helps ensure smoother UI performance, a stable system design, and a reliable user experience. By understanding the strengths and limitations of each TFT interface, developers can confidently choose the best option for their embedded display project.