Overview
Just Add Power Decoders monitor the HDMI Hot Plug Detect (HPD) status of the connected display. HPD indicates whether the display is presenting an active HDMI connection to the Decoder.
Checking the HPD status can help verify whether the Decoder detects a connected display. This information is useful when troubleshooting HDMI connectivity, display power behavior, or control system automation.
Applies To: Omega Series, Ultra Series, and MaxColor Series Decoders.
Note: This command reports HDMI Hot Plug Detect (HPD) status rather than the display's actual power state. Some displays continue asserting HPD while in standby, causing them to appear connected even though the screen is off.
Before You Begin
- Ensure you can access the Decoder. If needed, see How to Access a Device.
- Connect to the Decoder using Telnet. For instructions, see How to Telnet to a Device using PuTTY.
- Verify the Decoder is powered on and connected to the display.
Check HDMI Connection Status
- Open a Telnet session to the desired Decoder.
- Execute the following command:
cat /sys/devices/platform/display/monitor_info | grep "attached=y" -cThis command reads the Decoder's internal monitor_info status file and reports whether the connected display is asserting HDMI Hot Plug Detect (HPD).
Command Results
| Result | Description |
|---|---|
| 0 | No display is asserting HPD. The display may be powered off, disconnected, connected through a faulty HDMI cable, or otherwise not presenting an active HDMI connection. |
| 1 | A display is asserting HPD and an active HDMI connection has been detected. |
Example Output
user/local/bin# cat /sys/devices/platform/display/monitor_info | grep "attached=y" -c
1
The example above indicates that an active HDMI connection has been detected.
user/local/bin# cat /sys/devices/platform/display/monitor_info | grep "attached=y" -c
0
The example above indicates that no active HDMI connection has been detected.
Common Uses
This command is commonly used to:
- Verify whether a display is physically connected.
- Determine whether a display is asserting HDMI Hot Plug Detect (HPD).
- Troubleshoot HDMI cable or display connection issues.
- Confirm whether a display has responded to a power command.
- Incorporate display status into custom scripts or third-party control system logic.
Troubleshooting
If the command returns 0 unexpectedly:
- Verify the display is powered on.
- Inspect the HDMI cable between the Decoder and the display.
- Test with a known-good HDMI cable.
- Confirm the correct HDMI input is selected on the display.
- Test with another display to determine whether the issue follows the display or the Decoder.
- If an AV receiver, HDMI splitter, or other intermediary device is installed between the Decoder and display, verify that it is powered on and operating correctly.
Important: Display manufacturers implement standby behavior differently. Some displays continue asserting HPD while in standby, while others remove HPD completely. Because of this, HPD should be treated as an indication of HDMI connection status rather than an absolute indication of display power state.
Additional Information
The command returns a single numeric value, making it suitable for use in shell scripts, automation workflows, and third-party control systems that need to determine whether a display is asserting HDMI Hot Plug Detect (HPD).
