HDMI issues like no signal, dropouts, or missing ARC/CEC often come from a wrong pin, swapped pair, or flipped plug vs receptacle view. This article explains the 19-pin Type A layout, pin numbering, and signal groups (TMDS, DDC/EDID, CEC, +5 V, HPD, grounds). It also covers Type C and Type D changes with pin tables, diagrams, and checks.
HDMI Connector Pinout Basics
HDMI connectors have small metal contacts inside them. Each contact carries a specific signal, such as video, audio, control data, or power. Most HDMI connectors use 19 pins. These 19 pins carry digital video and audio together through one cable. They also carry control signals and a small 5-volt power line.
HDMI Connector Types and Pin Counts
The Common 19-Pin HDMI Connectors
The most common HDMI connectors all use 19 pins:
• Type A - Standard HDMI
• Type C - Mini HDMI
• Type D - Micro HDMI
• Type E - Automotive HDMI
Even though these connectors are different sizes, they carry the same 19 signals. The signal functions stay the same. Only the physical shape and pin placement change. Type E is made for vehicles. It has a stronger outer shell and a locking feature to prevent vibration from loosening the connection.
Less Common HDMI Types
| HDMI Type | Pins | Description |
|---|---|---|
| Type B | 29 | The dual-link version is defined in the standard, but used |
| Type E | 19 | Automotive version with locking design |
Understanding HDMI Pin Numbering
Two-Row Staggered Pin Layout
HDMI connectors use two staggered rows of pins instead of one straight row. One row is slightly offset from the other. This makes the connector smaller but can also make the numbering pattern harder to see at first. PINs also depend on how the connector is drawn:
• Some diagrams show the front of the plug (cable end).
• Others show the front of the receptacle (panel or PCB connector).
When the view changes, the pins can seem to flip from left to right. This often confuses when reading pinout diagrams.
Plug vs Receptacle Views
Before you use an HDMI pinout diagram, check which side you are looking at:
• Front view of the receptacle
• Front view of the plug
These views can look like mirror images of each other. In one drawing, Pin 1 may be on the left; in another, it may appear on the right. To avoid mistakes, always compare the diagram with the connector’s datasheet or footprint drawing. That way you match signals to pins in the correct direction.
HDMI Pin Functions by Group
Grouping the 19 Pins Makes the Pinout Easier
Instead of treating the HDMI connector as 19 separate pins, it helps to view it as a few functional groups. This makes the pinout easier to read and verify. Grouping also reduces mistakes when matching signals, since related pins tend to sit together and work as a set.
TMDS Data Channels and TMDS Clock
• TMDS Data Channels (0, 1, 2): Three high-speed differential pairs that carry video, embedded audio, and packet-based control data.
• TMDS Clock: One high-speed differential pair that provides the timing reference for the TMDS data channels.
• TMDS Shield/Ground Pins: Each TMDS channel includes a nearby shield/ground reference pin to support a stable return path and reduce noise.
Control and Side-Band Lines
• DDC (Display Data Channel): I²C SCL and SDA lines used to read EDID, so supported modes can be identified.
• CEC (Consumer Electronics Control): Single-wire control line used for basic command signaling between connected devices.
• ARC / HEC / HEAC (optional): Features that share pins in certain HDMI versions, supporting audio return and Ethernet-related functions when implemented.
Power, Status, and Grounding Roles
• +5 V: Supplies power for EDID/DDC-related circuitry and can support some active adapters within a limited current range.
• HPD (Hot Plug Detect): Status signal that indicates a connected device is present and ready, which can trigger EDID reads and link setup.
• Grounds and Shields: Provide reference and return paths for both high-speed TMDS signals and low-speed control lines.
Power and Reference Quick Table (Type A)
| Category | Typical Pins (Type A) | Function |
|---|---|---|
| +5 V Power | Pin 18 | Provides +5 V (typically up to ~50 mA) for EDID/DDC logic and some adapters |
| Hot Plug Detect (HPD) | Pin 19 | Presence/ready signal that can trigger EDID reads and link setup |
| TMDS Shields / Grounds | Pins 2, 5, 8, 11 | Shield/return reference for TMDS differential pairs |
| Control Ground | Pin 17 | Shared ground reference for CEC, DDC, and related control functions |
Standard HDMI Type A 19-Pin Pinout
| Pin | Signal (common naming) | Brief Function |
|---|---|---|
| 1 | TMDS Data2+ | High-speed data channel 2 (positive) |
| 2 | TMDS Data2 Shield | Ground/shield reference for Data2 |
| 3 | TMDS Data2− | High-speed data channel 2 (negative) |
| 4 | TMDS Data1+ | High-speed data channel 1 (positive) |
| 5 | TMDS Data1 Shield | Ground/shield reference for Data1 |
| 6 | TMDS Data1− | High-speed data channel 1 (negative) |
| 7 | TMDS Data0+ | High-speed data channel 0 (positive) |
| 8 | TMDS Data0 Shield | Ground/shield reference for Data0 |
| 9 | TMDS Data0− | High-speed data channel 0 (negative) |
| 10 | TMDS Clock+ | Clock channel (positive) |
| 11 | TMDS Clock Shield | Ground/shield reference for clock |
| 12 | TMDS Clock− | Clock channel (negative) |
| 13 | CEC | Consumer Electronics Control bus |
| 14 | ARC/HEC/Reserved* | Role depends on HDMI version and feature support |
| 15 | DDC SCL | I²C clock for EDID/DDC |
| 16 | DDC SDA | I²C data for EDID/DDC |
| 17 | Ground (CEC/DDC/HEAC) | Control/side-band ground reference |
| 18 | +5 V | +5 V supply (limited current) |
| 19 | HPD / ARC/HEC* | Hot Plug Detect; ARC/HEC role varies by version |
Mini HDMI Type C Pinout Differences
What Stays the Same vs What Changes?
Mini HDMI (Type C) uses the same 19 HDMI signals as Type A, but the connector is smaller. To fit this smaller body, the pins are rearranged. The signal roles stay the same, but the PINs and positions change. Always check the datasheet for the exact Type C connector on your board before you assign nets.
Type C Signals by Group
| Type C Pin Range | Signal Group | Notes |
|---|---|---|
| TMDS pins (multiple) | Data2 / Data1 / Data0 pairs + shields | Same signal roles as Type A, but placed on different pins |
| TMDS clock pins | Clock differential pair + shield | Same signal role as Type A, but placed on different pins |
| Control pins | CEC + DDC (SCL/SDA) | Same functions, but PINs differ |
| Power/status pins | +5 V + HPD | Same functions, but pin numbers differ |
| Grounds | TMDS and control grounds | Grounds are still used, but their locations change |
Micro HDMI Type D Pinout Layout
Type D Is the Smallest 19-Pin HDMI Connector
Micro HDMI (Type D) is the smallest HDMI connector that still supports all 19 signals. The pins are packed close together, and the body is very small. Because of this, orientation matters a lot. When reading a Type D diagram, always check if you are seeing the plug or the receptacle so you do not flip the pin order.
Type D Signals by Group
| Pins (Type D, Grouped View) | Signal Group |
|---|---|
| TMDS groups | Data2 / Data1 / Data0 differential pairs + shields |
| TMDS clock group | Clock differential pair + shield |
| Control group | CEC, DDC SCL/SDA, control ground |
| Power/status | +5 V, HPD |
HDMI Pinout Use Cases and Troubleshooting Checklist
Applying HDMI Pinout in Real Hardware
Once you see the pins as groups, it becomes much easier to design and debug HDMI hardware: Keep TMDS pairs matched and routed as true differential pairs. Wire control and power pins to the right places so +5 V, HPD, and DDC can bring up the link. Getting the groups and orientation right prevents many “no signal” and random dropout problems.
Design and Integration Uses
Custom panels and bulkhead connectors
Match Type A, Type C, or Type D pin mapping carefully, and confirm the connector view to avoid mirrored plug vs receptacle mistakes.
Adapters and converters
Keep TMDS pairs matched and confirm the required control pins are connected to avoid no signal and missing functions.
PCB routing and test points
Keep TMDS pairs short and matched, and provide access to DDC lines to support EDID checks during debugging.
HDMI Pinout Troubleshooting Checklist
No video and no EDID detection
Check +5 V and HPD first, then confirm continuity on DDC SCL and SDA.
EDID reads but no picture
Check TMDS data and clock pairs for opens, shorts, swapped pairs, or reversed polarity.
Sparkles, snow, or dropouts
Look for weak TMDS signal quality, often linked to ground/shield problems, cable damage, or impedance breaks.
CEC or ARC fails, but the video works
Check continuity on CEC, the related ARC/HEC/HEAC pins (if used), and the control ground.
Mechanical damage signs
Bent pins or cracked joints can break one line while others still work, leading to partial or unstable operation.
Conclusion
HDMI pinouts make more sense when the 19 pins are grouped by role: TMDS pairs carry video and audio, DDC reads EDID, CEC/ARC uses side-band lines, and +5 V with HPD helps the link start. For faults, confirm the connector view first, then check +5 V/HPD, DDC SCL/SDA, and TMDS pairs for swaps, opens, or reversed polarity.
Frequently Asked Questions [FAQ]
Are DDC, CEC, and HPD 5 V signals?
No. DDC and CEC are low-voltage control lines. HPD is a status line. Only Pin 18 is +5 V power.
Can Pin 18 (+5 V) power devices?
Only small loads. Too much draw can cause no EDID, no signal, or dropouts.
Is eARC the same as ARC?
No. They are different modes, and video can work even when ARC/eARC fails.
Why do some pins say “ARC/HEC/Reserved”?
Those pins change roles based on HDMI features and version support.
What two pins should be checked first with a multimeter?
Pin 18 (+5 V) and Pin 19 (HPD).
Why does HDMI work at low resolution but fail at high resolution?
Higher modes need cleaner TMDS signaling; cable loss, bad shielding/ground, or connector issues show up first.
