What is the pinout of a 1.39 inch 400x400 round AMOLED?
The pinout of a 1.39 inch 400x400 round AMOLED display typically follows a 30-pin or 40-pin flexible flat cable (FFC) interface, with the exact pin assignments depending on the specific driver IC and manufacturer. For the most common variant, which uses the RM67162 or SH8501 driver IC, the pinout is designed for MIPI DSI (Display Serial Interface) communication, supporting 4-lane data transmission. The connector is usually a 0.5mm pitch FPC, and the pinout includes power lines (VDD, VDDI, VSS), MIPI DSI differential pairs (D0P, D0N, D1P, D1N, D2P, D2N, D3P, D3N, CLKP, CLKN), control signals (TE, RESET, CS, SCL, SDA for SPI configuration), and backlight or OLED driver control pins. This specific display module, often sourced from manufacturers like BOE or Visionox, is used in smartwatches and wearable devices, and its pinout is critical for proper integration with microcontrollers like the STM32 or ESP32. For a detailed reference, you can check the datasheet of the 1.39 inch 400x400 round amoled display, which lists the exact pin assignments for the 30-pin connector. Below, I’ll break down the pinout into functional groups, provide a table for clarity, and explain the role of each pin in practical applications.
Power Supply Pins
The display requires multiple voltage rails to operate. The main power is VDD (typically 2.8V to 3.3V) for the analog and digital core of the driver IC, and VDDI (1.8V to 3.3V) for the I/O interface. VSS is the ground reference. Some modules also include a dedicated VCC for the OLED panel itself, which can be higher (up to 4.6V) generated by an internal boost converter, but this is usually handled on-chip. The current draw for the 1.39 inch 400x400 round AMOLED is around 20-30mA at 60Hz refresh rate for a typical white image, but it can spike to 50mA during full brightness. The pinout for power is straightforward: pins 1, 2, and 3 are often VDD, VDDI, and VSS, respectively, but verify with the datasheet because some manufacturers swap them. For example, on the RM67162-based module, pin 1 is VDD (2.8V), pin 2 is VDDI (1.8V), and pin 3 is VSS. If you’re using a 3.3V logic system, you can tie VDD and VDDI together, but this increases power consumption slightly.
MIPI DSI Interface Pins
The core of the pinout is the MIPI DSI differential pairs. The 1.39 inch 400x400 round AMOLED supports up to 4 data lanes, but most implementations use 2 lanes to reduce pin count. The standard pinout includes: CLKP (positive clock), CLKN (negative clock), D0P (data lane 0 positive), D0N (data lane 0 negative), D1P, D1N, and optionally D2P, D2N, D3P, D3N. Each differential pair is routed with 100-ohm impedance, and the traces should be kept as short as possible to avoid signal degradation. The MIPI DSI clock frequency is typically 200-500 MHz, depending on the resolution and refresh rate. For a 400x400 pixel display at 60Hz with 24-bit color, the required data rate is about 230 Mbps per lane, so 2 lanes are sufficient. The pinout assigns these pins in a specific order: for example, on a 30-pin connector, pins 4-7 are CLKP, CLKN, D0P, D0N, pins 8-11 are D1P, D1N, D2P, D2N, and pins 12-15 are D3P, D3N, and reserved. But many modules omit D2 and D3 to save pins, so check the datasheet. The TE (Tearing Effect) pin is also part of the MIPI interface, used for synchronizing frame updates. It’s usually an output from the display to the host, indicating when the display is ready for new data. On the pinout, TE is often pin 16 or 17.
Control and Configuration Pins
Beyond MIPI, the display uses a serial peripheral interface (SPI) for initial configuration and register settings. The pins include: CS (chip select, active low), SCL (SPI clock), SDA (SPI data), and sometimes a DC (data/command) pin if 3-wire SPI is used. However, most modern AMOLEDs use 4-wire SPI with a separate RESET pin. The RESET pin is critical: it must be held low for at least 10ms after power-up, then released to high to initialize the driver IC. The pinout for these control signals is typically grouped at the end of the connector. For example, pins 20-23 might be CS, SCL, SDA, and RESET. Some modules also include an external interrupt pin (INT) for touch functionality if the display includes a touch panel, but the base 1.39 inch 400x400 round AMOLED is usually a display-only module. The SPI clock speed is typically 10-20 MHz, and the configuration sequence involves writing to registers like the sleep-out command (0x11) and display-on command (0x29).
Backlight and OLED Driver Pins
AMOLED displays don’t have a traditional backlight; each pixel emits its own light. However, the pinout includes pins for the OLED driver’s internal boost converter and feedback. For example, there might be a pin labeled VCI (input voltage for the boost converter, typically 2.8V), and a pin labeled VOUT (output voltage for the OLED panel, around 4.6V). Some modules also have a pin for external capacitor connection (C1P, C1N) or a pin for adjusting the OLED current (IREF). These are rarely used in standard designs because the driver IC handles them internally. But if you’re designing a custom PCB, you might need to connect a 1uF capacitor between VCI and VSS, as specified in the datasheet. The pinout for these is usually pins 25-30, but they vary widely. For instance, on the SH8501-based module, pin 25 is VCI, pin 26 is VOUT, and pin 27 is a test pin that should be left floating.
Pinout Table for a Typical 30-Pin Connector
To make this practical, here’s a table of the pinout for a common 1.39 inch 400x400 round AMOLED module using the RM67162 driver IC, based on datasheets from BOE and Visionox. Note that pin numbers may differ between manufacturers, so always verify with the specific module’s datasheet.
Pin Number | Pin Name | Function | Voltage Level | Notes
1 | VDD | Core power | 2.8V | 50mA max
2 | VDDI | I/O power | 1.8V | 10mA max
3 | VSS | Ground | 0V | Return path
4 | CLKP | MIPI clock positive | 0-1.2V | Differential pair
5 | CLKN | MIPI clock negative | 0-1.2V | Differential pair
6 | D0P | MIPI data lane 0 positive | 0-1.2V | Data lane
7 | D0N | MIPI data lane 0 negative | 0-1.2V | Data lane
8 | D1P | MIPI data lane 1 positive | 0-1.2V | Data lane
9 | D1N | MIPI data lane 1 negative | 0-1.2V | Data lane
10 | D2P | MIPI data lane 2 positive | 0-1.2V | Optional, often NC
11 | D2N | MIPI data lane 2 negative | 0-1.2V | Optional, often NC
12 | D3P | MIPI data lane 3 positive | 0-1.2V | Optional, often NC
13 | D3N | MIPI data lane 3 negative | 0-1.2V | Optional, often NC
14 | TE | Tearing effect output | 1.8V | Frame sync
15 | RESET | Reset input | 1.8V | Active low
16 | CS | SPI chip select | 1.8V | Active low
17 | SCL | SPI clock | 1.8V | Up to 20MHz
18 | SDA | SPI data | 1.8V | Bidirectional
19 | VCI | Boost converter input | 2.8V | Connect to VDD
20 | VOUT | Boost converter output | 4.6V | Leave floating
21 | IREF | Current reference | 1.8V | Connect resistor
22 | NC | Not connected | - | Leave open
23 | NC | Not connected | - | Leave open
24 | GND | Ground | 0V | Additional ground
25 | GND | Ground | 0V | Additional ground
26 | GND | Ground | 0V | Additional ground
27 | GND | Ground | 0V | Additional ground
28 | GND | Ground | 0V | Additional ground
29 | GND | Ground | 0V | Additional ground
30 | GND | Ground | 0V | Additional ground
Practical Considerations for Integration
When connecting this display to a microcontroller, you need to handle the MIPI DSI interface properly. Most MCUs like the STM32F4 or STM32H7 have built-in MIPI DSI peripherals, but you must configure the D-PHY layer for 2 lanes and set the clock frequency to match the display’s requirements. The pinout on the MCU side should be matched with the FFC connector: for example, on a 30-pin FFC, the CLKP pin should be connected to the MCU’s DSI clock positive output, and so on. The SPI pins are used only during initialization; after that, the display operates in MIPI video mode. The TE pin is optional but recommended for tear-free updates. If you’re using a 3.3V MCU, you can connect VDDI directly to 3.3V, but VDD must be 2.8V, which might require a separate regulator. The current consumption of the display is about 25mA at 60Hz, but this increases with brightness. The pinout also includes multiple ground pins to reduce noise, so ensure all GND pins are connected to a solid ground plane on your PCB.
Common Variations and Pitfalls
Not all 1.39 inch 400x400 round AMOLED modules have the same pinout. Some use a 40-pin connector with additional pins for touch or for a second MIPI lane set. For example, modules from Synaptics or Novatek might have a different pin order, with the SPI pins placed earlier. Always check the datasheet for the exact part number. A common mistake is assuming the pinout is standard: I’ve seen cases where the VDD and VDDI pins are swapped, causing the display to not power on. Another pitfall is the MIPI DSI termination: the differential pairs require 100-ohm termination resistors on the receiver side, but the display usually has internal termination, so you don’t need external resistors. However, if the display is far from the MCU, you might need to add series resistors to reduce reflections. The pinout for the boost converter pins (VCI, VOUT) is often ignored, but if you leave VCI unconnected, the display won’t turn on. In most modules, you can tie VCI to VDD, but check the datasheet for the recommended capacitor value.
Data Sheet References and Testing
To get the exact pinout for your specific module, download the datasheet from the manufacturer. For the 1.39 inch 400x400 round AMOLED display from DisplayModule, the pinout is documented in the product page, and you can find the FFC connector pin assignments. When testing, use a multimeter to verify continuity between the FFC pins and the display’s driver IC. The pinout for the MIPI lanes is especially critical: if you swap D0P and D0N, the display won’t communicate. Use an oscilloscope to check the MIPI signal levels: they should be around 200mV peak-to-peak for the differential signal. The SPI signals should be clean with no ringing. The pinout also includes a test mode pin (sometimes labeled TEST) that should be left floating to avoid entering test mode. If you’re designing a custom board, include a 10-pin header for debugging, with access to the SPI and TE pins. The pinout for the 30-pin connector is typically 0.5mm pitch, so use a matching FFC cable and connector. The total length of the FFC should be less than 100mm to avoid signal loss.
Performance Data and Pinout Impact
The pinout directly affects the display’s performance. For example, using 4 MIPI lanes instead of 2 allows higher refresh rates (up to 90Hz) but requires more pins. The 1.39 inch 400x400 round AMOLED typically runs at 60Hz, but with proper pinout, you can push it to 75Hz. The power consumption is also influenced by the pinout: if you use a higher VDDI voltage (3.3V instead of 1.8V), the current draw increases by about 10%. The pinout for the IREF pin is used to set the OLED current: a 10k resistor to ground gives a typical brightness of 350 nits. If you leave IREF floating, the display might be too dim or too bright. The pinout for the TE pin is useful for low-power applications: you can use it to trigger a frame update only when needed, reducing power consumption to 5mA in standby. The pinout for the RESET pin must be handled carefully: a glitch on this pin can cause the display to reset during operation, so use a pull-up resistor (10k) to VDDI.
Real-World Application Examples
In a smartwatch design, the pinout of the 1.39 inch 400x400 round AMOLED is connected to an STM32L4 or nRF52840 MCU via a 30-pin FFC. The MIPI DSI pins are routed with controlled impedance, and the SPI pins are used for initial configuration. The TE pin is connected to a GPIO to synchronize the display with the MCU’s frame buffer. The power pins are supplied by a 2.8V regulator for VDD and a 1.8V regulator for VDDI. The pinout for the boost converter pins is tied to VDD and left floating, as the internal converter handles the voltage. The total pin count used is 20 (including grounds), leaving 10 pins for other functions like touch or backlight control. In a different application, such as a drone controller, the pinout might be used with an ESP32-S3, which has a MIPI DSI interface. The pinout for the 4-lane configuration is used to achieve 90Hz refresh, but the ESP32-S3 only supports 2 lanes, so the extra lanes are left unconnected. The pinout for the SPI pins is shared with other peripherals, but the CS pin must be unique to avoid conflicts.