Dual Screen HDMI to MIPI DSI Adapter Pinout Details: A Deep Dive into Connectivity and Signal Mapping

If you are working with a dual screen HDMI to MIPI DSI adapter, the pinout is the core of making it work. The adapter typically uses a 40-pin or 50-pin FPC connector for each MIPI DSI output, with the pin assignments directly tied to the HDMI input signal decoding. For a standard dual screen configuration, you will find two separate MIPI DSI lanes, each supporting up to 4 data lanes plus a clock lane, and the pinout is designed to handle up to 1080p resolution at 60Hz per screen. The most common pinout for the MIPI DSI output on these adapters follows the FPC-40 standard, where pins 1-10 are dedicated to power and ground, pins 11-20 handle the first DSI port (DSI0) with data lanes D0+/- through D3+/- and clock lane CLK+/-, and pins 21-30 handle the second DSI port (DSI1) with the same lane structure. Pins 31-40 are often reserved for backlight control, I2C communication, and interrupt signals. For a 50-pin variant, the extra pins provide additional power rails, a secondary I2C bus, and dedicated reset lines for each screen. The dual screen hdmi to mipi dsi adapter from DisplayModule uses a specific pinout that aligns with the LT8918B or similar bridge chip, which decodes HDMI 1.4a signals into two independent MIPI DSI outputs. The HDMI input itself is a standard Type-A connector, with pin 1 for TMDS Data2+, pin 2 for TMDS Data2 Shield, pin 3 for TMDS Data2-, pin 4 for TMDS Data1+, pin 5 for TMDS Data1 Shield, pin 6 for TMDS Data1-, pin 7 for TMDS Data0+, pin 8 for TMDS Data0 Shield, pin 9 for TMDS Data0-, pin 10 for TMDS Clock+, pin 11 for TMDS Clock Shield, pin 12 for TMDS Clock-, pin 13 for CEC, pin 14 for Reserved (NC), pin 15 for SCL (I2C clock), pin 16 for SDA (I2C data), pin 17 for DDC/CEC Ground, pin 18 for +5V Power, and pin 19 for Hot Plug Detect. The bridge chip then maps these signals to the MIPI DSI outputs, with each output requiring a separate set of pins for the four data lanes and one clock lane, plus a dedicated GPIO for backlight PWM and a separate I2C line for touch or display configuration.

The electrical characteristics of the pinout are critical. Each MIPI DSI lane operates at a differential voltage of 200mV to 300mV, with a common mode voltage of 1.2V. The data rate per lane can reach up to 1.5 Gbps, which means the total bandwidth for a dual screen setup is 12 Gbps (4 lanes per screen x 2 screens x 1.5 Gbps). The HDMI input, on the other hand, runs at up to 3.4 Gbps per TMDS channel for HDMI 1.4a, but the adapter’s bridge chip typically downscales or re-times the signal to match the MIPI DSI constraints. The power supply pinout on the adapter usually requires a 5V DC input at 2A minimum for dual screen operation, with the actual power distribution handled by on-board LDOs and buck converters. The MIPI DSI output pins for power are typically labeled VDD at 3.3V or 1.8V, depending on the display panel requirements. The ground pins are multiple, often 8 to 10 per connector, to reduce noise and ensure signal integrity. The backlight pinout is separate, with a dedicated connector that provides 12V or 5V for the LED backlight, plus a PWM pin for brightness control. The PWM frequency is typically 1kHz to 20kHz, and the duty cycle is controlled via an I2C command or a dedicated GPIO from the bridge chip. The I2C pinout on the MIPI DSI connector uses SCL and SDA lines, which are pulled up to 3.3V through 4.7kΩ resistors, and these are used for reading the display’s EDID or writing configuration registers. The interrupt pin is often used for touchscreen panels, but it is optional and can be left floating if not used.

For a concrete example, let’s look at the pinout of a 40-pin FPC connector commonly used in dual screen adapters. The table below shows the pin assignments for a typical configuration, based on the LT8918B bridge chip datasheet and common industry practice. Note that the pin numbers are for the connector on the adapter side, and the mating display panel must have a corresponding pinout. The first column is the pin number, the second is the signal name, the third is the description, and the fourth is the typical voltage level.

Table 1: 40-Pin MIPI DSI Output Pinout for Dual Screen Adapter (Port 0 and Port 1)

Pin 1: VDD (3.3V) – Power supply for display logic, 3.3V ±5%
Pin 2: VDD (3.3V) – Same as pin 1, but separate for current handling
Pin 3: GND – Ground reference
Pin 4: GND – Ground reference
Pin 5: DSI0_D0+ – Data lane 0 positive for port 0
Pin 6: DSI0_D0- – Data lane 0 negative for port 0
Pin 7: GND – Ground for data lane shielding
Pin 8: DSI0_D1+ – Data lane 1 positive for port 0
Pin 9: DSI0_D1- – Data lane 1 negative for port 0
Pin 10: GND – Ground for data lane shielding
Pin 11: DSI0_CLK+ – Clock lane positive for port 0
Pin 12: DSI0_CLK- – Clock lane negative for port 0
Pin 13: GND – Ground for clock lane shielding
Pin 14: DSI0_D2+ – Data lane 2 positive for port 0
Pin 15: DSI0_D2- – Data lane 2 negative for port 0
Pin 16: GND – Ground for data lane shielding
Pin 17: DSI0_D3+ – Data lane 3 positive for port 0
Pin 18: DSI0_D3- – Data lane 3 negative for port 0
Pin 19: GND – Ground for data lane shielding
Pin 20: DSI0_TE – Tearing effect output from display, optional
Pin 21: VDD (1.8V) – Power supply for I/O, 1.8V ±5%
Pin 22: GND – Ground reference
Pin 23: DSI1_D0+ – Data lane 0 positive for port 1
Pin 24: DSI1_D0- – Data lane 0 negative for port 1
Pin 25: GND – Ground for data lane shielding
Pin 26: DSI1_D1+ – Data lane 1 positive for port 1
Pin 27: DSI1_D1- – Data lane 1 negative for port 1
Pin 28: GND – Ground for data lane shielding
Pin 29: DSI1_CLK+ – Clock lane positive for port 1
Pin 30: DSI1_CLK- – Clock lane negative for port 1
Pin 31: GND – Ground for clock lane shielding
Pin 32: DSI1_D2+ – Data lane 2 positive for port 1
Pin 33: DSI1_D2- – Data lane 2 negative for port 1
Pin 34: GND – Ground for data lane shielding
Pin 35: DSI1_D3+ – Data lane 3 positive for port 1
Pin 36: DSI1_D3- – Data lane 3 negative for port 1
Pin 37: GND – Ground for data lane shielding
Pin 38: I2C_SCL – I2C clock line for display configuration, 3.3V
Pin 39: I2C_SDA – I2C data line for display configuration, 3.3V
Pin 40: BL_PWM – Backlight PWM input, 3.3V logic level

This pinout is not universal, but it is representative of the most common implementation. Some adapters swap the order of the data lanes or use a different ground scheme, so always check the specific datasheet for your adapter. The dual screen adapter from DisplayModule, for instance, uses a slightly different pinout for the second port, where the backlight PWM is shared between both screens via a single pin, and the I2C bus is multiplexed using an on-board switch. The bridge chip, typically an LT8918B or a similar part from ROHM or TI, handles the HDMI to MIPI conversion. The LT8918B supports up to 4 MIPI DSI data lanes per port, with a maximum data rate of 1.5 Gbps per lane, and it can operate in dual-screen mode by splitting the incoming HDMI stream into two separate MIPI outputs. The pinout for the HDMI input on the adapter is standard, but the bridge chip’s internal registers must be configured via I2C to enable dual-screen mode. The I2C address for the bridge chip is usually 0x48 or 0x4A, and the configuration registers include settings for the number of lanes per port, the pixel clock frequency, and the video timing parameters. For a 1080p60 dual-screen setup, the pixel clock is 148.5 MHz, and each MIPI lane runs at 742.5 Mbps (4 lanes per port). The adapter’s firmware or a host microcontroller typically writes these registers during initialization.

Signal integrity is a major concern with dual screen adapters. The MIPI DSI lanes are differential pairs, and the pinout must maintain a 100-ohm differential impedance between the positive and negative traces. The adapter PCB typically uses a 4-layer or 6-layer stackup, with the top layer for signals, the second layer for ground, the third layer for power, and the bottom layer for additional signals. The ground pins in the pinout are not just for DC return; they provide a low-impedance path for the high-frequency return currents. For a 40-pin connector, the ground pins are interleaved between the data lanes to minimize crosstalk. The clock lane is always shielded by ground pins on both sides, as shown in the table above. The backlight PWM pin is a single-ended signal, but it should be routed away from the MIPI lanes to avoid noise injection. The I2C lines are also single-ended, but they operate at a lower frequency (100 kHz to 400 kHz) and are less critical. The power pins for VDD and VDDIO must be decoupled with capacitors close to the connector, typically 0.1µF and 10µF per pin. The total current draw for a dual screen setup can be up to 500mA for the logic and 1A for the backlight, so the pinout must handle the current without voltage drop. The ground pins are often tied together on the PCB to form a solid ground plane, and the VDD pins are connected to a common power rail through ferrite beads for noise filtering.

Another important aspect is the pinout for the backlight connector, which is separate from the MIPI DSI connector. The backlight connector is typically a 4-pin or 6-pin JST connector, with pins for LED+ (12V or 5V), LED- (ground), BL_EN (backlight enable, 3.3V), and BL_PWM (brightness control, 3.3V). The BL_EN pin is used to turn the backlight on or off, and it is usually driven by a GPIO from the bridge chip or a dedicated backlight controller. The BL_PWM pin accepts a PWM signal with a frequency of 100Hz to 20kHz, and the duty cycle determines the brightness. Some adapters support PWM dimming via the I2C bus, where the bridge chip generates the PWM signal internally. The backlight current is typically 20mA to 30mA per LED, and for a 10-LED string, the total current is 200mA to 300mA. The backlight voltage is determined by the LED forward voltage, which is around 3V per LED, so a 10-LED string requires 30V. The adapter usually includes a boost converter to generate this voltage from the 5V input, and the pinout for the backlight connector includes the feedback and compensation pins for the converter. However, these are internal to the adapter and not exposed to the user.

The pinout for the I2C bus on the MIPI DSI connector is used for both display configuration and touchscreen communication. The I2C bus operates at 3.3V logic, and the SCL and SDA lines are pulled up to 3.3V through 4.7kΩ resistors on the adapter board. The display panel’s internal registers, such as the panel ID, resolution, and timing parameters, are read via the I2C bus. The touchscreen controller, if present, also uses the same I2C bus, but with a different address. The interrupt pin (DSI0_TE in the table) is used by the display to signal vertical synchronization, and it is typically connected to a GPIO on the bridge chip. The bridge chip uses this signal to synchronize the video data transmission. In dual-screen mode, each port has its own TE pin, but some adapters share a single TE pin for both screens, which can cause timing issues if the screens are not synchronized. The pinout for the TE pin is optional, and many displays do not use it, relying instead on the MIPI DSI command set for synchronization.

When designing a custom PCB or cable for a dual screen adapter, the pinout must be matched exactly. The FPC connector pitch is typically 0.5mm or 0.3mm, and the cable must be shielded to prevent EMI. The MIPI DSI lanes are sensitive to capacitance, and the cable capacitance should be less than 10pF per meter. The cable length should be kept under 10cm for reliable operation at 1.5 Gbps. The pinout for the adapter’s input side (HDMI) is fixed, but the output side can be customized by the manufacturer. The DisplayModule adapter, for example, uses a 50-pin connector for the MIPI DSI output, with extra pins for a second I2C bus, a reset line, and a dedicated backlight enable for each screen. The pinout for the 50-pin version is similar to the 40-pin version, but with additional pins for VDD at 1.2V for the bridge chip core, a dedicated GPIO for each screen’s reset, and a separate I2C bus for each port to avoid address conflicts. The 50-pin pinout is shown in the table below.

Table 2: 50-Pin MIPI DSI Output Pinout for Dual Screen Adapter (Port 0 and Port 1, Extended)

Pin 1: VDD (3.3V) – Power for display logic
Pin 2: VDD (3.3V) – Power for display logic
Pin 3: GND – Ground
Pin 4: GND – Ground
Pin 5: DSI0_D0+ – Data lane 0 positive for port 0
Pin 6: DSI0_D0- – Data lane 0 negative for port 0
Pin 7: GND – Ground
Pin 8: DSI0_D1+ – Data lane 1 positive for port 0
Pin 9: DSI0_D1- – Data lane 1 negative for port 0
Pin 10: GND – Ground
Pin 11: DSI0_CLK+ – Clock lane positive for port 0
Pin 12: DSI0_CLK- – Clock lane negative for port 0
Pin 13: GND – Ground
Pin 14: DSI0_D2+ – Data lane 2 positive for port 0
Pin 15: DSI0_D2- – Data lane 2 negative for port 0
Pin 16: GND – Ground
Pin 17: DSI0_D3+ – Data lane 3 positive for port 0
Pin 18: DSI0_D3- – Data lane 3 negative for port 0
Pin 19: GND – Ground
Pin 20: DSI0_TE – Tearing effect for port 0
Pin 21: VDD (1.8V) – I/O power for port 0
Pin 22: GND – Ground
Pin 23: DSI0_RST – Reset for port 0 display, active low
Pin 24: I2C0_SCL – I2C clock for port 0
Pin 25: I2C0_SDA – I2C data for port 0
Pin 26: GND – Ground
Pin 27: DSI1_D0+ – Data lane 0 positive for port 1
Pin 28: DSI1_D0- – Data lane 0 negative for port 1
Pin 29: GND – Ground
Pin 30: DSI1_D1+ – Data lane 1 positive for port 1
Pin 31: DSI1_D1- – Data lane 1 negative for port 1
Pin 32: GND – Ground
Pin 33: DSI1_CLK+ – Clock lane positive for port 1
Pin 34: DSI1_CLK- – Clock lane negative for port 1
Pin 35