3.5 Inch Display Modules: 320 × 240, 320 × 480 or 480 × 640, SPI or RGB

By the SuccessLCD Engineering Team · Updated November 7, 2026

A 3.5 inch display in a handheld, instrument or control panel is almost always a TFT in one of three formats: 320 × 240 landscape, 320 × 480 portrait or 480 × 640 portrait. Each step doubles the pixels, and with them the frame buffer and the bandwidth the host has to find. That makes the format the first decision and the interface the second: SPI is comfortable at 320 × 240, gets slow at 320 × 480, and 480 × 640 wants a parallel RGB bus. Our catalogue has eleven 3.5-inch references, including a capacitive-touch module at 850 cd/m² and transflective panels for outdoor use.

320 × 240, 320 × 480 or 480 × 640

A 3.5-inch diagonal is 88.9 mm. How that splits into width and height depends on the aspect ratio, and the pixel pitch follows. The 320 × 240 column uses the active area from the S35001D drawing; the other two are nominal for a 3.5-inch diagonal.

At normal reading distance 116 ppi shows its pixels on small text and thin lines, but it is fine for numbers, icons and simple graphics. 165 ppi is the sweet spot for menus with real text. 229 ppi looks sharp from close up, and you pay for it with four times the pixels of 320 × 240.

The 3.5-inch references

Two body sizes cover most of the list: 76.9 × 63.9 mm for the landscape panels and 64 × 85 mm for the portrait ones. Pick the orientation early, because it fixes the enclosure. S35001D is the most fully documented: 850 cd/m² typical with an anti-glare polarizer, a 54-pin LCD FPC and a separate 10-pin touch FPC, both at 0.50 mm pitch, −20 to +70 °C operating. The compact S350MHQS, S350MLQS and the S350MPWH FOG assembly (84 × 53.25 mm) are further outlines to check if the two standard bodies do not fit.

SPI or RGB: what the host can feed

When a reference says “SPI + RGB”, the SPI port usually carries the initialization commands and the RGB bus carries the pixels. A panel can also run on SPI alone if its driver IC has frame memory. The two behave very differently once the screen starts changing.

Over RGB, the same 320 × 240 panel needs only 76,800 × 60 ≈ 4.6 MHz of active pixel clock for 60 Hz, a little more once the datasheet’s blanking is added, and the frame rate no longer depends on what changed. The price is about 20 GPIOs for a 16-bit bus, a host with an LCD controller and a frame buffer the host keeps refreshing. The frame buffer RAM calculator and the ILI9341 vs ST7789 vs ILI9488 comparison go further into this.

Rule of thumb from those numbers: SPI for 320 × 240 with partial updates, RGB for animation or for anything at 480 × 640.

Showing camera video: the CCIR656 option

S350MTQV lists CCIR656 next to RGB + SPI. CCIR656, now ITU-R BT.656, is an 8-bit YCbCr 4:2:2 video stream at 27 Mword/s with the sync codes embedded in the data, the format that standard-definition PAL and NTSC video decoders output. On a 3.5-inch screen that is useful for a reversing camera, a door camera or an inspection probe, where the picture comes from a video decoder rather than a graphics processor. Ask for the input timing in the datasheet before you assume a particular decoder will match.

Sunlight: transmissive or transflective

A transmissive panel relies entirely on its backlight, so outdoors it needs brightness: S35001D gets to 850 cd/m² typical, which is usually workable in shade and under an overcast sky. A transflective panel also reflects ambient light, so the brighter the sun, the better it reads, at the cost of colour saturation indoors. S350FPQI, S350FPQI-01 and S350FLVH-01 are our 3.5-inch transflective references. The transflective display guide and sunlight-readable TFT guide compare the two routes properly.

Touch: capacitive, resistive or none

S35001D carries a G+G capacitive panel with an FT5446 controller on I²C and a 0.70 mm chemically strengthened cover. It is the choice for a glass front and multi-touch. The resistive version of S350MLQZ works with a stylus and thick gloves and ignores water, at the price of lower light transmission and a plastic top surface that wears. Plenty of instruments need no touch at all. Capacitive vs resistive touch sets out the trade-offs.

3.5 inch Raspberry Pi and Arduino displays

Many 3.5 inch Raspberry Pi displays sold as add-ons are SPI boards. Waveshare’s 3.5inch RPi LCD (A), a typical one, is 480 × 320 with an XPT2046 resistive touch controller and plugs straight onto the 40-pin header, with the LCD and touch sharing one SPI bus. Arduino 3.5-inch shields are similar hobby boards, on SPI or a parallel MCU bus depending on the model. They are good for proving out a user interface. The SPI numbers above explain why full-screen animation on them is sluggish, and why a production design at 320 × 480 or above usually moves to an RGB panel driven by a processor with an LCD controller.

Video: 3.5 Inch Displays, 320 × 240, 320 × 480 or 480 × 640, SPI or RGB

This SuccessLCD explainer compares the three 3.5-inch formats to scale, works out the SPI frame-rate ceiling, explains when to move to RGB, and covers CCIR656 camera input, sunlight, touch and the hobby boards used for prototypes.

3.5 Inch Display FAQs

Related engineering guides: small TFT LCD comparison, 1.3 to 3.5 inches, ILI9341 vs ST7789 vs ILI9488, transflective displays and 5-inch TFT displays.