SPI vs RGB vs MIPI LCD Interfaces Compared

HZY Engineering Notes · 2026-09-10

Choosing an LCD interface is one of the earliest decisions in a display project, and it shapes almost everything that follows: the host microcontroller or processor you can use, the flex cable and connector, the maximum resolution and refresh rate, and how much design effort goes into electromagnetic compatibility. This article compares the three interfaces that come up most often in small and medium TFT projects — SPI, RGB and MIPI — and briefly notes where QSPI and MCU (8080) interfaces fit.

Quick comparison at a glance

Pin count

• SPI: typically 4 to 6 signals (SCLK, MOSI, CS, DC, optionally MISO and RESET). A 4-wire SPI link needs very few host pins, which is why it is common on small panels.
• QSPI: adds two or four data lanes to the SPI clock and chip-select, so roughly 6 to 8 signals for a meaningful speed increase.
• MCU / 8080 parallel: 8 or 16 data lines plus control signals (CS, RS/DC, WR, RD), so typically 12 to 20 pins.
• RGB: 16, 18 or 24 data bits in parallel plus HSYNC, VSYNC, DE and PCLK — roughly 20 to 30 signals depending on colour depth.
• MIPI DSI: one clock lane plus one to four differential data lanes. A typical 2-lane link uses about 6 to 8 pins, and because the lanes are differential, pin count scales slowly with bandwidth.

Bandwidth and achievable resolution / frame rate

• SPI is the slowest option. It is comfortable at small resolutions — 128x160, 240x240, 240x320 — at modest frame rates, and it is often used for UI panels rather than video.
• QSPI multiplies SPI throughput by using multiple data lanes; it sits between SPI and RGB and suits small-to-mid panels that need faster refresh than plain SPI allows.
• MCU / 8080 is faster than SPI but is limited by the parallel bus width and the host's write cycles; it remains common on character and graphic modules and on older COG designs.
• RGB is a streaming interface: the host continuously feeds pixels at the pixel clock, and frame rate follows directly from resolution and clock. It handles 4.3 inch 800x480 and larger panels well.
• MIPI DSI is a packet-based, high-speed differential link. It is the natural fit for higher pixel counts — 480x480 round panels, 800x640 half-circle panels, 1080x1080 square panels and bar-type displays in the 360x960 class — where a parallel RGB bus would become wide and awkward.

Host requirements

• SPI / QSPI: almost any microcontroller works. No special display peripheral is required, and a bit-banged or peripheral-driven SPI block is enough. Initialisation is a register write sequence over the same bus.
• MCU / 8080: needs a parallel memory-style bus, common on 8/16-bit MCUs and on some MPUs with an external memory interface.
• RGB: the host must provide a continuous pixel clock and timing signals. This usually means an MCU with an LCD-TFT controller (LTDC) or an MPU/SoC with a display controller. There is no frame buffer inside the panel, so the host must supply data continuously.
• MIPI DSI: the host needs a dedicated DSI controller, which in practice means an application processor or a microcontroller with DSI support. Plain SPI-only MCUs cannot drive a MIPI panel directly.

EMI and trace length

• SPI and QSPI: single-ended signals; keep traces short and, at higher QSPI clocks, treat them as controlled-impedance lines. EMI is manageable but rises with clock rate.
• MCU / 8080: many parallel lines switching together produce broad-spectrum emissions; short flex runs are advisable.
• RGB: 16–24 data lines plus clock switching at the pixel rate create the most demanding EMI environment of the three. Flex length should be kept as short as the mechanical design allows, with ground returns and careful routing.
• MIPI DSI: differential lanes with embedded clocking; the signalling is designed for high speed over a flex, but impedance control, matched pair lengths and careful layout are still required. In practice MIPI tolerates somewhat longer, narrower interconnects than a wide RGB bus at the same pixel throughput, which is one reason it dominates in compact, high-resolution products.

SPI: the simplest path to a small TFT

SPI is the interface most engineers reach for first, and for good reason. Four wires plus power and ground are enough to bring up a small colour display. Register configuration, pixel writes and simple graphics commands all travel over the same link.

The trade-off is throughput. At small resolutions the data volume is modest, so SPI is entirely practical — a 2.4 inch 240x320 SPI TFT is a volume model for exactly this reason, pairing a well-understood resolution with a minimal host connection. Similarly, a 1.3 inch 240x240 panel using the ST7789V2 driver is a typical SPI design where board space and pin count matter more than refresh rate.

SPI panels also suit products where the display is updated occasionally rather than streamed: instrument readouts, small appliances, handheld tools and status displays. Because the interface is so widely supported, firmware porting between microcontrollers is straightforward. You can browse SPI options in our SPI TFT display range.

QSPI deserves a mention here because it is often the upgrade path when SPI is too slow but RGB is too complex. By using multiple data lanes, QSPI raises throughput while keeping the pin count and host requirements close to plain SPI. A 1.85 inch 320x386 QSPI module at 600 cd/m2 is an example of a small, bright panel that benefits from the extra bandwidth without moving to a parallel bus.

RGB: the workhorse for mid-size TFTs

RGB is a parallel, continuous-scan interface. The host outputs pixels at a fixed pixel clock, gated by HSYNC, VSYNC and DE, and the panel's driver IC streams them to the glass. There is no on-panel frame buffer to manage, so the host must keep feeding data.

That makes RGB a natural match for mid-size panels where the pixel count is high enough that SPI would be too slow, but where a MIPI host is not available or not desired. A 4.3 inch 800x480 RGB module at 600 cd/m2 is a representative example — a resolution and size band where RGB timing is well understood and display controllers with LTDC outputs are common.

RGB is available in 16, 18 and 24-bit variants, which lets a design trade colour depth against pin count. An 18-bit RGB connection is a frequent compromise for 5 inch class panels, while 24-bit is used where full colour depth is required and the host has the pins to spare. The main design constraints are the wide flex, the pin budget on the host, and EMI from many lines switching at the pixel clock. Keep the flex short, provide good ground return, and route the clock with care. Our RGB LCD display range covers the panel sizes where this interface is typically used.

MIPI DSI: high resolution in a narrow connection

MIPI DSI is a high-speed serial interface built around differential lanes. Because it is packet-based and uses a small number of lanes, it scales to higher resolutions without a proportional increase in pins or flex width. It also carries configuration commands over the same link, so no separate control bus is needed.

The cost is host complexity: a DSI controller is required. That generally means an application processor or a microcontroller with native DSI support. Once that is available, MIPI opens up panel formats that would be awkward on RGB — round displays such as a 2.1 inch 480x480, square formats such as a 7 inch 1080x1080, half-circle shapes like a 3.54 inch 800x640 for home appliances, and bar-type panels such as a 6.2 inch 360x960.

MIPI is also the practical choice when the mechanical envelope is tight. A narrow flex with two data lanes and a clock pair is easier to route through a hinge or a slim housing than a 24-bit RGB bus. See the MIPI LCD display range for panels using this interface.

Mapping size and resolution bands to interfaces

The table below is a practical guide rather than a rule; the right choice always depends on host capability, enclosure and update rate.

• Up to about 1.5 inch, up to 240x240: SPI is usually sufficient. Example: 1.3 inch 240x240 with ST7789V2 over SPI.
• Around 2 to 2.8 inch, 240x320: SPI remains common for UI panels. Example: 2.4 inch 240x320 SPI TFT, a volume model. QSPI becomes attractive if faster updates are needed.
• Small panels needing more speed: QSPI. Example: 1.85 inch 320x386 QSPI at 600 cd/m2.
• Around 3.5 to 5 inch, 320x480 to 800x480: RGB is the typical choice. Example: 4.3 inch 800x480 RGB at 600 cd/m2. Transflective TFT options in 2.4, 2.8, 3.7 and 5.0 inch are also available where readability in ambient light matters.
• Higher pixel counts and unusual shapes: MIPI. Examples: round 2.1 inch 480x480, 7 inch 1080x1080, bar-type 6.2 inch 360x960, half-circle 3.54 inch 800x640.
• Character and monochrome graphic modules: these typically use MCU/8080 parallel or SPI depending on the controller. A 128x64 COG module with the ST7567 in a 28.5x20.0 mm outline and 1602 character modules with HD44780-class controllers are long-established examples where the interface is chosen to match the host's parallel or serial capability.

Other interfaces worth knowing

MCU / 8080 parallel remains relevant for character modules 8x2, 16x2, 20x2, 16x4, 20x4 and 40x2, for monochrome graphic modules at 128x64, 192x64, 240x128 and 240x160, and for many COG assemblies. It is simple to drive from an 8-bit MCU but consumes a lot of pins.

Parallel 8080 on COG is a common way to bond a bare driver die to glass with a compact flex, especially in cost-sensitive designs.

Custom segment LCDs in TN, HTN, STN, FSTN and VA are a separate category: they use static or multiplexed drive rather than a pixel interface, and are specified by viewing direction (6h or 12h), polarizer type (transmissive, transflective or reflective), drive voltage (2.8, 3.0, 3.3 or 5 V) and connector style (metal pin, zebra or FPC), with operating range of -30 to +80 °C.

Practical selection checklist

• Start with the host. If it has no LCD controller and no DSI, SPI or QSPI is the realistic path. If it has an LTDC, RGB is open. If it has DSI, MIPI is available.
• Size the bandwidth from resolution and required refresh rate, then add margin for UI animation.
• Count pins and flex width early — connector and cable choices often constrain the enclosure more than the panel itself.
• Plan EMI: shorter flex, ground returns, controlled impedance for high-speed lanes.
• Confirm brightness and optical requirements alongside the interface; many panels are available at different brightness levels.
• Consider customisation: interface, FPC outline, touch (capacitive or resistive on selected models), brightness and size can all be adapted. Typical timelines are drawings in about three days, samples in about two weeks and mass production in about five to six weeks. Standard listed models often start at very small MOQs, and custom projects are quoted per design.

Where QSPI and MCU fit in one sentence each

QSPI is the middle ground: near-SPI simplicity with enough bandwidth for small panels that need quicker updates. MCU/8080 parallel is the traditional choice for character and monochrome graphic modules and for compact COG designs where the host already has a parallel bus.

Bringing it together

SPI, RGB and MIPI are not competing standards so much as tools for different points on the size, resolution and host-capability curve. SPI and QSPI keep pin counts low and work with almost any microcontroller, which makes them ideal for small colour panels and simple user interfaces. RGB offers high throughput and predictable timing for mid-size panels, at the cost of pin count and EMI care. MIPI delivers high resolution and unusual shapes over a narrow differential connection, provided the host has a DSI controller.

HZY's TFT LCD module range covers 0.71 inch to 10.1 inch, alongside monochrome graphic modules, character modules, custom segment LCDs and LED backlights, with interfaces including SPI, QSPI, MIPI, RGB (16/18/24-bit), MCU and parallel 8080. Common driver ICs across the range include ST7789/ST7789V2, ST7701, ST7735S, ST7365, ST7567, NV3002B and EK79001. Manufacturing is supported by ISO 9001, IATF 16949 and ISO 14001 systems, with certificates available upon request, and every module undergoes 100% functional inspection before shipment.

If you are weighing interfaces for a new design, send your panel requirements or target specification to our contact page — size, resolution, interface preference, brightness and host platform are enough for us to suggest a suitable module or a custom configuration.