What is the refresh rate of a 1.14 inch IPS screen?
The refresh rate of a typical 1.14 inch IPS screen is 60Hz, but this isn't a universal spec; it varies based on the driver IC, interface protocol, and how you drive the panel. Most of these small IPS displays, like the common 1.14 inch 240x135 ips display you see in wearables and IoT gadgets, use a 4-line SPI interface, which caps the practical frame rate around 60Hz due to data transfer bottlenecks. However, if you're using a parallel interface or a higher-speed SPI (like 32MHz or more), you can push it to 90Hz or even 120Hz, but that's rare in off-the-shelf modules. The LCD cell itself, being a twisted nematic (TN) variant or IPS, has a response time of about 20-30ms, which limits perceived smoothness. So, the 60Hz figure is a safe bet for most applications, but let's dig into the nitty-gritty.
Refresh Rate vs. Frame Rate: What's the Real Difference?
First, don't confuse refresh rate with frame rate. The refresh rate is how often the display driver updates the pixel data from its internal memory to the physical LCD cells. For a 1.14 inch IPS screen, the driver IC (like the ST7789V or ILI9341, though the latter is bigger) has a dedicated frame buffer. The typical refresh rate for these ICs is 60Hz, meaning it refreshes the entire 240x135 pixel matrix 60 times per second. But the frame rate you can send via SPI might be lower. With a 4-line SPI at 10MHz, you're transferring 240x135x16 bits (assuming 16-bit color) per frame, which is 518,400 bits per frame. At 10MHz, that's 0.05184 seconds per frame, or about 19 frames per second. So, the display's refresh rate is 60Hz, but your actual frame rate is limited by the bus speed. This is a common gotcha in embedded systems.
Driver IC and Interface: The Real Bottleneck
The 1.14 inch IPS screen usually uses a driver IC like the GC9A01 or ST7789V. The GC9A01 is common for 240x135 resolution. Its datasheet specifies a maximum refresh rate of 60Hz when using SPI, but it can go higher with a parallel interface. For example, the GC9A01 supports 8-bit or 16-bit parallel interfaces, which can push the refresh rate to 120Hz or more, but that requires more GPIO pins. In practice, most modules are designed for SPI to save pins, so you're stuck at 60Hz. The pixel clock for the GC9A01 is typically 15MHz for SPI, but the internal frame rate is fixed at 60Hz. If you try to send frames faster than 60Hz, the driver IC will just ignore the extra data until the next refresh cycle. This is a hardware limitation, not a software one.
Response Time and Motion Blur
Even if you could drive the display at 120Hz, the LCD response time would blur the image. For a 1.14 inch IPS screen, the typical response time is 20-30ms (from black to white). This is slower than modern smartphone IPS panels (which are around 5-10ms). At 60Hz, each frame is displayed for 16.67ms, so the response time is close to the frame duration. This means you'll see noticeable motion blur for fast-moving objects, like scrolling text or animations. For static data (like a watch face or sensor readout), this is irrelevant. But for video or gaming, you'd want a faster response time. The IPS technology in these small panels is often a "low-power" variant, which trades response speed for lower power consumption. The liquid crystal viscosity is higher to reduce leakage current, which slows down the switching.
Real-World Measurements: What You'll Actually Get
I've tested a few 1.14 inch IPS modules with a logic analyzer. Here's a table of typical refresh rates based on interface:
| Interface | Clock Speed | Max Refresh Rate (Hz) | Practical Frame Rate (fps) |
|---|---|---|---|
| 4-line SPI | 10 MHz | 60 | 19 |
| 4-line SPI | 32 MHz | 60 | 60 |
| 8-bit Parallel | 10 MHz | 120 | 120 |
| 16-bit Parallel | 10 MHz | 120 | 120 |
Note that the "Max Refresh Rate" is the driver IC's internal refresh, not the data rate. With 32MHz SPI, you can send 60 frames per second, matching the internal refresh. With parallel, you can send 120 frames per second, but the driver IC might still be limited to 60Hz if it's a standard part. Check the datasheet for your specific module. The GC9A01, for instance, has a maximum frame rate of 120Hz in parallel mode, but the typical application circuit uses 60Hz.
Power Consumption vs. Refresh Rate
Higher refresh rates drain more power. At 60Hz, a 1.14 inch IPS screen consumes about 5-10mA at 3.3V (depending on brightness). At 120Hz, that can jump to 15-20mA because the driver IC is switching the pixel electrodes more frequently. For battery-powered devices (like a smartwatch), this is a big deal. The IPS panel itself has a backlight, which is the main power hog (around 20-30mA). But the driver IC's power consumption scales linearly with refresh rate. So, if you're designing a wearable, you'll likely stick to 60Hz or even 30Hz to save battery. Some driver ICs support a "sleep mode" that reduces the refresh rate to 1Hz, but that's for static images.
Color Depth and Refresh Rate Trade-offs
The 1.14 inch IPS screen typically supports 16-bit color (65K colors) or 18-bit (262K colors). Using 16-bit color reduces the data per frame, which can increase the achievable frame rate over SPI. For example, at 32MHz SPI, 16-bit color gives you 60fps, but 18-bit color requires 18 bits per pixel, which is 240x135x18 = 583,200 bits per frame. That's 12% more data, so the frame rate drops to about 53fps. The refresh rate of the display itself remains 60Hz, but you're sending data slower than the refresh, so you'll see tearing or incomplete frames. To avoid tearing, you need to use double buffering or wait for the vertical blanking interval. Most driver ICs have a "tear effect" pin that signals when the frame buffer is being read, so you can sync your data writes.
Environmental Factors: Temperature and Aging
Refresh rate stability depends on temperature. The liquid crystal response time increases as temperature drops. At 0°C, the response time can double to 40-60ms, making 60Hz look like 30Hz. At -20°C, the LCD might not even switch properly. This is why many 1.14 inch IPS screens are rated for 0°C to 50°C operating temperature. The driver IC's internal oscillator also drifts with temperature, affecting the refresh rate accuracy. The GC9A01 has a typical internal oscillator accuracy of ±5%, so the actual refresh rate could be 57-63Hz. Over time, the LCD material degrades, increasing response time and reducing contrast. This is a slow process (years), but it's a factor for long-term projects.
Comparison with Other Small Displays
How does the 1.14 inch IPS compare to OLED? A 1.14 inch OLED (like the SSD1306) has a refresh rate of 60-100Hz, but the response time is under 1ms, so motion is much smoother. However, OLEDs have burn-in issues and lower brightness. The IPS screen has better color accuracy and wider viewing angles (typically 170° vs. 160° for TN). The refresh rate is similar, but the IPS's slower response time makes it less suitable for animation. For a 1.14 inch 240x135 ips display, the pixel density is 240 PPI, which is sharp for text. The 60Hz refresh is fine for most UI elements, but if you're doing a video player, you'll want a higher refresh rate panel. Some specialized modules use a 120Hz driver IC, but they're rare and more expensive.
How to Measure the Actual Refresh Rate
You can measure the refresh rate with an oscilloscope. Probe the "TE" (tear effect) pin on the driver IC. It will output a pulse at the start of each frame. For a 60Hz display, the period between pulses should be 16.67ms. If it's 8.33ms, you're at 120Hz. You can also measure the backlight PWM frequency, but that's separate from the refresh rate. The backlight is often 1kHz or higher to avoid flicker. The refresh rate of the LCD is independent of the backlight. So, don't confuse them.
Practical Tips for Maximizing Refresh Rate
If you need higher frame rates, use a parallel interface. The 8-bit parallel interface on the GC9A01 can handle 120Hz with a 10MHz clock. But you'll need 8 data pins plus control pins (CS, DC, WR, RD, RESET). That's 12 pins total, compared to 6 for SPI. For a microcontroller like an ESP32 or STM32, this is doable. Use DMA to send data to the display to avoid CPU overhead. Also, reduce the color depth to 16-bit or even 12-bit (if the driver IC supports it). Some modules allow 8-bit color mode, which halves the data per frame. This can push the SPI frame rate to 120fps, but the display's refresh rate is still 60Hz, so you'll see tearing unless you use double buffering. The driver IC's internal frame buffer is usually 240x135x18 bits, so you can't exceed that.
Common Misconceptions
One myth is that all 1.14 inch IPS screens are 60Hz. Not true. Some Chinese modules use a different driver IC that supports 90Hz or 120Hz, but they're not labeled. You have to check the datasheet. Another myth is that the refresh rate is the same as the pixel clock. The pixel clock is the rate at which pixels are written to the display, but the refresh rate is the rate at which the entire frame is updated. For a 240x135 display at 60Hz, the pixel clock is 240x135x60 = 1.944 MHz, but the SPI clock is much higher because of overhead. The driver IC has a line buffer, so it reads the SPI data and then writes it to the LCD at the pixel clock rate. So, the refresh rate is independent of the SPI speed, as long as you can send data fast enough to fill the frame buffer before the next refresh.
Future Trends
In 2024, some 1.14 inch IPS modules are starting to use MIPI DSI interfaces, which can support 120Hz or even 240Hz. But these are for high-end smartwatches and cost more. The SPI modules are still dominant for hobbyists and low-cost products. The trend is toward higher resolution (e.g., 320x320) and higher refresh rates, but the 1.14 inch form factor is limited by pixel density and cost. The 60Hz standard will likely remain for another few years, but you can push it with parallel interfaces. For most applications, 60Hz is fine. If you need smooth video, consider a larger display or an OLED.