Overview

CEC (Consumer Electronics Control) is an HDMI feature that allows devices to send control commands over the HDMI cable. In a simple point-to-point setup, this allows a TV remote to control a connected source device.

CEC works reliably when a single source is connected to a single display. However, in a distributed HDMI over IP system, one source may be routed to multiple displays. Without proper control management, a single CEC command (such as Play or Power On) could affect multiple zones unintentionally.

To prevent this, Just Add Power devices isolate native HDMI CEC communication and instead allow CEC commands to be intentionally passed to a specific endpoint device through IP control.

CEC over IP

In a Just Add Power system, the physical CEC link between the source and display is interrupted at the Encoder and Decoder.

• CEC commands from a source stop at the Encoder.
• CEC commands from a display stop at the Decoder.

CEC is then treated similarly to IR over IP or Serial over IP. A control system sends a CEC command to a specific Just Add Power device, which then forwards the command to the connected source or display.

This ensures CEC commands are zone-specific and predictable.

Access

CEC commands are entered through the Command Line Interface (CLI) by telnetting to the IP address of the appropriate Encoder or Decoder.

All commands are case-sensitive.

Built-In Commands

The following CEC commands are built into Just Add Power devices and are supported in standard drivers:

cec_tv_on.sh

POST /command/cec/tv on

cec_tv_off.sh

POST /command/cec/tv off

cec_watch_me.sh

POST /command/cec/bytes EF 82 10 00

cec_audio_off.sh

POST /command/cec/bytes E0 72 01

cec_audio_on.sh

POST /command/cec/bytes E0 72 00

CEC Mode Behavior Modification (cec_mode)

A configurable parameter called cec_mode allows modification of how the following built-in commands behave:

• cec_tv_on.sh
• cec_tv_off.sh

This setting allows the system to automatically send an additional cec_watch_me.sh command before or after a power command. This can improve reliability on displays that require an active input selection event in addition to a power command.

Available Options

Multiple options may be applied simultaneously. When more than one is set, all selected behaviors will execute.

wake_on

watch_on

wake_off

Applying the Setting

Use the following syntax in the CLI:

Apply one option:

astparam s cec_mode wake_on

Apply two options:

astparam s cec_mode wake_on wake_off

Apply all options:

astparam s cec_mode wake_on wake_off watch_on

After applying the setting, reboot the device for changes to take effect.

Custom Commands

Any valid CEC command can be sent through Just Add Power if the correct hexadecimal sequence is known.

Format

CEC commands consist of hexadecimal byte pairs. The first pair identifies the sending and receiving logical addresses. Subsequent pairs define the command and any associated parameters.

Example:

EF 82 10 00

To send a custom command:

CEC_SEND_BYTES EF 82 10 00

Finding CEC Codes

Because CEC is part of the HDMI specification, many codes are standardized. However, manufacturer implementation varies. Always test commands before deployment.

A commonly used CEC lookup tool is:

www.cec-o-matic.com

CEC-O-Matic is published and maintained by INCYMA. All credit for that tool belongs to its respective owners.

Common Custom Codes

Begin all entries below with CEC_SEND_BYTES