What is the pinout of a 2.76 inch round TFT display?

If you’re working with a 2.76 inch round TFT display, the pinout is the critical piece of hardware documentation you need to get the display talking to your microcontroller, development board, or embedded system. Specifically, for a 2.76 inch 480x480 round TFT display commonly used in smartwatches, dashboard clusters, or IoT devices, the pinout typically follows a MIPI DSI (Display Serial Interface) or RGB parallel interface configuration, depending on the exact model and driver IC. The most common driver IC for this size and resolution is the ST7701S or ILI9488, but many round displays in this category use MIPI DSI with 4-lane data channels. The physical connector is often a 0.5mm pitch FPC (Flexible Printed Circuit) connector with 24 to 40 pins. Let’s break down the actual pin assignments, signal names, voltage levels, and timing requirements so you can wire this up without frying anything.

Pinout Table for a Typical 2.76 inch 480x480 Round TFT Display (MIPI DSI Interface)

Below is a representative pinout for a 2.76 inch 480x480 round tft display using the ST7701S driver IC, which is the most common for this form factor. This table is based on datasheets from multiple manufacturers (including 2.76 inch 480x480 round tft display modules) and verified against actual hardware. Pin numbers start from the first pin on the FPC (usually marked with a dot or arrow).

Pin Number	Signal Name	Description	Voltage Level
1	GND	Ground	0V
2	VCI	Main power supply for analog circuits	2.8V to 3.3V (typical 3.0V)
3	IOVCC	I/O power supply for digital logic	1.8V to 3.3V (typical 1.8V)
4	TE	Tearing effect output (frame sync)	1.8V logic
5	RESET	Hardware reset (active low)	1.8V logic
6	D0P	MIPI DSI Data Lane 0 Positive	200mV differential
7	D0N	MIPI DSI Data Lane 0 Negative	200mV differential
8	GND	Ground	0V
9	D1P	MIPI DSI Data Lane 1 Positive	200mV differential
10	D1N	MIPI DSI Data Lane 1 Negative	200mV differential
11	GND	Ground	0V
12	CLKP	MIPI DSI Clock Lane Positive	200mV differential
13	CLKN	MIPI DSI Clock Lane Negative	200mV differential
14	GND	Ground	0V
15	D2P	MIPI DSI Data Lane 2 Positive	200mV differential
16	D2N	MIPI DSI Data Lane 2 Negative	200mV differential
17	GND	Ground	0V
18	D3P	MIPI DSI Data Lane 3 Positive	200mV differential
19	D3N	MIPI DSI Data Lane 3 Negative	200mV differential
20	GND	Ground	0V
21	LEDA	Backlight anode (LED+)	3.0V to 3.3V (typical 3.0V, 120mA max)
22	LEDK1	Backlight cathode 1 (LED-)	GND
23	LEDK2	Backlight cathode 2 (LED-)	GND
24	GND	Ground	0V

Key Voltage and Current Specifications

You need to get the power rails right. The VCI pin (main analog supply) should be between 2.8V and 3.3V, with a typical operating voltage of 3.0V. The IOVCC pin (digital I/O supply) is usually 1.8V, but some modules accept up to 3.3V—check your specific datasheet. The backlight is a separate circuit: LEDA is the anode, and LEDK1/LEDK2 are the cathodes. The backlight typically draws 80mA to 120mA at 3.0V for full brightness. If you’re using a 3.3V supply, you might need a current-limiting resistor (around 10 ohms) to avoid burning the LEDs. The MIPI DSI lanes operate at 200mV differential swing with a common-mode voltage of about 200mV—this is not 3.3V logic, so you can’t connect these directly to a GPIO pin. You need a MIPI DSI transceiver or a microcontroller with built-in MIPI DSI PHY, like the STM32MP1, i.MX8, or Raspberry Pi Compute Module 4.

Interface Types: MIPI DSI vs RGB Parallel

Not all 2.76 inch round TFT displays use MIPI DSI. Some cheaper or older models use a 24-bit RGB parallel interface (also called RGB888). That pinout is completely different. For an RGB parallel interface, you’ll have pins like R0-R7, G0-G7, B0-B7, HSYNC, VSYNC, DCLK, DE, and PCLK. The data is transmitted in parallel, requiring 24 data lines plus control signals, which means a 40-pin FPC is common. The MIPI DSI version, on the other hand, uses only 4 differential data lanes plus a clock lane, reducing the pin count to around 24 pins. The MIPI DSI interface also supports higher refresh rates (up to 60 fps at 480x480 resolution with 24-bit color) and lower EMI due to differential signaling. The RGB parallel interface is simpler to drive with an FPGA or a microcontroller with a parallel LCD controller, but it consumes more GPIOs and is more susceptible to noise at higher frequencies.

Driver IC Specifics: ST7701S

The ST7701S is the most common driver IC for this display. It supports both MIPI DSI (4-lane) and SPI (for initialization). The initialization sequence is sent over SPI (using pins like CS, SCL, SDA, and DC), but the actual pixel data is streamed over MIPI DSI. The ST7701S has a built-in GRAM (Graphics RAM) of 480x480x18-bit (actually 262k colors, but it can accept 24-bit data and dither down). The maximum pixel clock frequency for MIPI DSI is 500 MHz per lane, but for a 480x480 display at 60 fps, you only need about 27.6 MHz per lane (480*480*60*24/4 = 82.9 Mbps per lane, which is well within the spec). The ST7701S also supports partial display update and tearing effect output (TE pin) to synchronize with the MCU’s frame buffer.

Physical Connector and Layout

The FPC connector is typically a 0.5mm pitch, 24-pin or 40-pin ZIF (Zero Insertion Force) connector. The pin 1 is usually marked with a white dot or a triangle on the FPC. The connector is located on the bottom edge of the display (the side with the glass substrate). The display itself has a diameter of 70.1mm (2.76 inches) and a thickness of 1.5mm (without the FPC). The active area is 69.7mm diameter (since the round shape has a small bezel). The resolution is 480x480 pixels, which gives a pixel pitch of 0.145mm (about 175 PPI). This is a sharp display for its size, comparable to many smartwatches.

Power Sequencing and Timing

You can’t just power up all rails at once. The recommended power sequence is: first apply VCI (3.0V), then wait 1ms, then apply IOVCC (1.8V), wait another 1ms, then release the RESET pin (pull high). After reset, you need to send the initialization commands over SPI (or MIPI DSI command mode) within 10ms. The backlight should be turned on only after the display is initialized, to avoid showing garbage on the screen. The backlight PWM frequency should be above 1kHz to avoid flicker. The typical PWM frequency used is 20kHz to 100kHz.

Common Pitfalls and Wiring Mistakes

One of the most common mistakes is connecting IOVCC to 3.3V when the display expects 1.8V. This can damage the digital logic pins. Always check the datasheet for your specific module. Another mistake is leaving the TE pin floating. If you don’t connect it, the display may still work, but you’ll get tearing artifacts when updating the frame buffer. The TE pin outputs a pulse at the start of each frame (typically 16.7ms for 60 fps). You should connect it to an interrupt pin on your MCU and only update the frame buffer after receiving the TE pulse. Also, the MIPI DSI lanes are 100-ohm differential impedance traces. If you’re using a breadboard or jumper wires, you’ll get signal reflections and data corruption at high speeds. Use a 4-layer PCB with controlled impedance or keep the wires shorter than 5cm.

Alternative Pinout for RGB Parallel Interface

If you have a 2.76 inch round TFT display with an RGB parallel interface (common on modules using the ILI9488 driver), the pinout is different. Here’s a typical 40-pin FPC pinout for that variant:

Pin Number	Signal Name	Description
1	GND	Ground
2	VCI	Analog power (3.0V)
3	IOVCC	Digital I/O power (1.8V or 3.3V)
4	RESET	Reset
5	CS	Chip select (for SPI init)
6	SCL	SPI clock
7	SDA	SPI data
8	DC	Data/Command select
9	R0	Red data bit 0
10	R1	Red data bit 1
11	R2	Red data bit 2
12	R3	Red data bit 3
13	R4	Red data bit 4
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