What is the resolution of a 2.4 inch resistive TFT display?

The resolution of a standard 2.4 inch resistive TFT display is almost universally 240x320 pixels, which is a QVGA (Quarter Video Graphics Array) format. This means the display has 240 pixels horizontally and 320 pixels vertically, giving a total of 76,800 pixels. The aspect ratio is 3:4, which is portrait-oriented by default, but many controllers allow you to rotate the orientation for landscape use. This resolution is not arbitrary; it dates back to early mobile phone and PDA designs where 240x320 was the sweet spot for readability and power efficiency. For a 2.4 inch diagonal, the pixel density works out to roughly 167 pixels per inch (PPI), calculated as the diagonal resolution (sqrt(240² + 320²) = 400 pixels) divided by 2.4 inches. That 167 PPI is noticeably lower than modern smartphone displays (which often exceed 400 PPI), but for a resistive touch interface, it’s entirely adequate. The individual pixels are visible under close inspection, especially for text or fine graphics, but the trade-off is cost and simplicity. The controller chip driving this resolution is typically the ST7789V or ILI9341, both of which support 16-bit or 18-bit color depth (65,536 or 262,144 colors). The 240x320 resolution is fixed at the hardware level; you cannot change it without swapping the panel itself. This resolution is also the reason why most 2.4 inch resistive TFTs are used in embedded systems, industrial controls, and retro gaming projects—they don’t need high-definition detail, but they do need reliable touch input and low power draw. If you’re looking for a specific product example, this 2.4 inch resistive tft display from DisplayModule uses the ST7789V controller and confirms the 240x320 resolution.

Let’s break down the technical details further. The 240x320 resolution directly impacts the display’s memory requirements. Each pixel, when using 16-bit color (RGB565), consumes 2 bytes of frame buffer memory. So the total frame buffer size is 240 x 320 x 2 = 153,600 bytes, or 150 KB. For 18-bit color (RGB666), it’s 240 x 320 x 3 = 230,400 bytes, or 225 KB. Most microcontrollers like the ESP32, STM32, or Arduino Mega have enough SRAM to handle this, but you still need to manage the buffer carefully. The ST7789V controller, for instance, has a built-in GRAM (Graphics RAM) of 172,800 bytes, which is exactly enough for 240x320 pixels at 18-bit color depth. If you try to use a higher resolution, the controller simply won’t support it. The 240x320 resolution also determines the maximum refresh rate. With a typical SPI interface running at 20 MHz, you can push data at about 2.5 MB per second. That translates to roughly 16 frames per second (fps) for full-screen updates at 16-bit color, or 10 fps at 18-bit. In practice, many applications update only portions of the screen, so the effective refresh rate feels faster. But if you’re animating a video or game, those numbers are a hard limit. The resistive touch layer adds another constraint: it’s analog, not digital, so the resolution of touch detection is determined by the ADC (Analog-to-Digital Converter) in your microcontroller, not the display itself. Typical 12-bit ADCs give you 4096 x 4096 touch points, but the overlay’s physical accuracy is around 0.5 mm, which is coarser than the pixel pitch of 0.15 mm. So you can’t reliably hit a single pixel with a resistive touch, but you can easily select a button or icon that’s 10 pixels wide.

From a historical perspective, the 240x320 resolution on a 2.4 inch resistive TFT became a de facto standard because of the Nokia 3310 and early Palm PDAs. Those devices used similar displays, and the manufacturing tooling stuck. Even today, you’ll find that nearly all 2.4 inch TFT modules from major suppliers like Winstar, Newhaven, or DisplayModule share the same 240x320 resolution. The only exception is a few niche panels that use 128x128 or 160x128, but those are usually monochrome or low-cost alternatives. The 240x320 resolution is also the minimum required to display a recognizable character in a 8x8 font grid; you can fit 30 characters per row and 40 rows per screen, which is enough for a simple text interface. For graphical user interfaces, the resolution allows for 40x40 pixel icons, which are small but functional. The pixel density of 167 PPI means that at a typical viewing distance of 30 cm, the human eye can resolve individual pixels, but it’s not distracting. The resistive touch layer adds a slight haze and reduces contrast by about 10-15%, but the 240x320 resolution remains sharp enough for most industrial and hobbyist uses.

Now, let’s talk about the physical constraints. The 2.4 inch diagonal measurement is the active area, not the entire module. The active area dimensions are typically 36.72 mm x 48.96 mm for a 240x320 panel, because each pixel is 0.153 mm wide and 0.153 mm tall (square pixels). That’s a standard pixel pitch for this size. The overall module size, including the bezel and resistive touch overlay, is usually around 42 mm x 60 mm, with a thickness of 3.5 to 4 mm. The resistive touch layer is a separate glass or plastic sheet with a transparent conductive coating (ITO), and it adds about 0.5 mm to the thickness. The resolution of the touch layer is not directly related to the display resolution; it’s an analog input that your microcontroller reads via two analog pins (one for X, one for Y). The ADC resolution determines how many discrete positions you can detect, but the physical accuracy is limited by the touch layer’s construction. Most resistive touch panels have a linearity error of about 1-2%, which means at 240x320, you can expect a touch accuracy of roughly ±3 pixels. That’s fine for button presses, but not for precise drawing or handwriting recognition. The 240x320 resolution also affects the viewing angle. TFT panels have a typical viewing angle of 60 degrees in all directions (measured from the center), but the contrast ratio drops off significantly beyond that. At 240x320, the pixel structure is more visible at extreme angles, but that’s a limitation of the TFT technology itself, not the resolution.

Let’s get into the electrical and interface details. The 240x320 resolution requires a specific set of timing parameters. For the ST7789V controller, the horizontal sync pulse width is 10 pixels, the back porch is 20 pixels, and the front porch is 10 pixels, giving a total horizontal cycle of 280 pixels (240 active + 40 blanking). Vertically, the sync pulse width is 10 lines, the back porch is 20 lines, and the front porch is 10 lines, giving a total vertical cycle of 360 lines (320 active + 40 blanking). The pixel clock frequency is typically 10 MHz, which results in a frame rate of about 60 Hz when using 16-bit color. But if you’re driving the display via SPI, the effective frame rate is lower because the SPI bus is half-duplex and slower. At 20 MHz SPI, you can achieve about 30 fps for full-screen updates, but only if you use a dedicated hardware SPI controller. If you’re bit-banging the SPI, you’ll be lucky to get 10 fps. The 240x320 resolution also determines the number of pins needed. Most 2.4 inch resistive TFT modules use a 16-pin or 18-pin interface, with 8 data lines for parallel mode or 4 lines for SPI. The resistive touch layer adds 4 more pins (X+, X-, Y+, Y-). So in total, you need 20 to 22 GPIO pins on your microcontroller. That’s a significant number, but it’s manageable on most boards.

From a practical standpoint, the 240x320 resolution is ideal for displaying sensor data, simple menus, or status indicators. For example, you can display a real-time graph of temperature readings with 240 data points horizontally, which is enough for a 24-hour trend at 6-minute intervals. Or you can show a 320-pixel tall bar graph for a vertical scale. The resolution also supports basic bitmap images, but you’ll need to store them in flash memory. A full-screen 240x320 image at 16-bit color takes 150 KB, which is a lot for an Arduino with 32 KB of flash. So you’d typically use compression or store images in external SPI flash. The resistive touch layer adds a layer of complexity: you need to calibrate the touch coordinates to the display coordinates. This involves a 4-point or 5-point calibration routine that maps the ADC values (0-4095) to the 240x320 pixel grid. The calibration matrix is usually stored in EEPROM. Without calibration, the touch points will be offset by 10-20 pixels, which is unacceptable for any UI. The 240x320 resolution also affects the font rendering. For a 16x16 pixel font, you can fit 15 characters per row and 20 rows, which is plenty for a text-based interface. For a 8x8 font, you get 30 characters per row and 40 rows, which is cramped but usable.

Let’s compare the 240x320 resolution to other common TFT sizes. A 1.8 inch TFT typically uses 128x160 pixels, which is half the resolution in each dimension. A 2.8 inch TFT often uses 320x240 pixels (landscape) or 240x320 (portrait), which is the same resolution but with a larger physical size, resulting in a lower PPI of 143. A 3.5 inch TFT uses 480x320 pixels, which is double the resolution and gives a PPI of 165. So the 2.4 inch 240x320 panel sits in a sweet spot: it’s small enough to be portable, but the resolution is high enough for basic graphics. The resistive touch layer adds durability; it can withstand 1 million touches in the same spot, according to typical datasheets. The 240x320 resolution is also compatible with most graphics libraries like Adafruit GFX, TFT_eSPI, and LVGL. These libraries assume a 240x320 frame buffer and provide functions for drawing shapes, text, and images. The library overhead is minimal because the resolution is fixed. For example, the TFT_eSPI library for ESP32 uses a 240x320 pixel buffer in PSRAM, which allows for double-buffering and smooth animations. The 240x320 resolution is also the basis for many retro game emulators, like the Game Boy Advance emulator, because the GBA had a 240x160 resolution in landscape mode. By rotating the 2.4 inch display, you can get exactly 240x320, which is close enough to the GBA’s 240x160 with some scaling.

Now, let’s look at the cost implications. A 2.4 inch resistive TFT with 240x320 resolution costs between $5 and $15 in single-unit quantities, depending on the brand and whether it includes a breakout board. The resistive touch layer adds about $1 to $2 compared to a non-touch version. The 240x320 resolution is the main reason for this low cost; higher resolutions like 480x320 would require a more expensive controller and more complex manufacturing. The 240x320 resolution also means the display can be driven by low-cost microcontrollers like the Arduino Uno or ESP8266, which have limited memory and processing power. For example, the Arduino Uno has only 2 KB of SRAM, which is not enough to hold a full 150 KB frame buffer. So you’d need to use a technique called “partial buffer” or “write-only” mode, where you send data directly to the display without storing it in RAM. That works fine for static images, but for animations, you’d need a microcontroller with more RAM, like the ESP32 (520 KB) or STM32 (192 KB). The 240x320 resolution is also the reason why many 2.4 inch displays use a 4-wire SPI interface, which is slower but uses fewer pins. The SPI clock speed is typically 10-20 MHz, which is fast enough for 240x320 at 30 fps. If you try to use a higher resolution, you’d need a parallel interface, which uses more pins and is more complex to wire.

Let’s examine the optical characteristics. The 240x320 resolution on a 2.4 inch panel gives a dot pitch of 0.153 mm, which means the center-to-center distance between adjacent pixels is 0.153 mm. That’s about the thickness of a human hair. The aperture ratio (the percentage of the pixel area that actually transmits light) is typically around 60-70% for a TFT panel, which means the black matrix between pixels is visible if you look closely. The 240x320 resolution also determines the maximum readable font size. For a 12-point font (which is 16 pixels tall), the characters are about 2.4 mm tall, which is readable at arm’s length. For a 8-point font (11 pixels tall), the characters are 1.7 mm tall, which is borderline for people with normal vision. The resistive touch layer adds a slight blur, so you might need to increase font sizes by 1-2 points. The contrast ratio of a typical 2.4 inch TFT is around 300:1 to 500:1, which is lower than IPS panels (1000:1) but acceptable for indoor use. The 240x320 resolution doesn’t affect the contrast ratio directly, but the pixel density does affect the perceived sharpness. At 167 PPI, the display is considered “retina” at a viewing distance of 30 cm, because the human eye can resolve about 1 arcminute, which corresponds to 167 PPI at that distance. So in theory, the 240x320 resolution is just enough for a sharp image at normal viewing distances. But in practice, the resistive touch layer and the lower contrast make it look less sharp than a modern smartphone.

Finally, let’s talk about the future of this resolution. The 240x320 on a 2.4 inch resistive TFT is not going away anytime soon. It’s a mature technology with billions of units produced for consumer electronics, automotive, and industrial applications. The 240x320 resolution is also the baseline for many embedded systems that need a simple user interface without the complexity of a high-resolution display. For example, 3D printers, CNC machines, and medical devices often use 2.4 inch resistive TFTs because they are reliable, cheap, and easy to interface. The 240x320 resolution is also the minimum required for a functional touchscreen keyboard, where each key needs to be at least 10x10 pixels. The resistive touch layer is preferred in harsh environments because it works with gloves and is resistant to dust and moisture. The 240x320 resolution is also supported by all major display controllers, including the ILI9341, ST7789, and HX8357. So if you’re designing a product, you can be confident that the 240x320 resolution will be available for years to come. The only downside is that the 240x320 resolution is not suitable for high-definition video or detailed graphics, but that’s not the intended use case. For a 2.4 inch resistive TFT, the 240x320 resolution is the perfect balance of cost, performance, and usability.