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The HDMI_CEC API defines the ability to get connected HDMI devices, send messages to those devices, and to be notified when messages are received from HDMI devices

HDMI-CEC is a protocol that provides high-level control functions between audio-visual devices connected over HDMI. CEC is a one-wire bidirectional serial bus based on industry-standard AV.Link protocol to perform control functions. All audio-visual sources are connected directly or indirectly to a display device as the ‘root’ in a tree-like structure.

Feature Summary

Hardware support for HDMI-CEC as specified in HDMI 1.4a
- CEC 4 – Electrical Specification
- CEC 5 – Signaling and Bit Timings
- CEC 6 – Frame Description
- CEC 7 – Reliable Communication Mechanisms
- CEC 8 – Protocol Extensions
- CEC 9 – CEC Arbitration
- CEC 10.1 – Physical Address Discovery
- CEC 11 – Switch Requirements

Send raw or formatted CEC messages on behalf of application
Provide received CEC messages to registered application listener
Get information about a device connected to HDMI input
Autonomously handle subset of CEC messages
Provide list of connected CEC capable device to application
Send "Feature Abort" response if message is not handled autonomously by RDK and message is not handled by application listener

Device Applicability

This feature applies to the following devices:

Hybrid
IP

Architecture Overview

RDK > HDMI CEC > image2017-10-12_19-56-27.png

Component Impacts

CEC Protocol Library

Translate application commands to CEC commands
Receive CEC commands and provide to application listeners
Autonomously respond to a subset of CEC messages

HDMI-CEC HAL

Abstract SoC CEC library from CEC Protocol Library

SoC CEC Driver

Serialize and send CEC commands
Receive CEC commands and provide to CEC Protocol Library
Send EDID to HDMI source
Provide HDMI input connect notification

Service Manager

Provide HDMI input connect notification via State Observer API.
Select select video source

Device Settings HAL

Provide HDMI event notification
Read/Modify/Write EDID
Add dsRegisterHdmiListener
Add dsSelectVideoSource
Add dsScaleVideoSource

SoC Video Pipeline

Source video from HDMI input

Design Details

RDK > HDMI CEC > image2017-10-12_20-11-51.png

Methods

Name	Parameters	Description
setEnabled	enabled : boolean	Enables or disables CEC
getEnabled	none	Returns true if CEC is enabled
setName	name : string	Sets the name of the STB device. The default name is "STB". It is recommended that the name of the device is set prior to enabling CEC.
getName	none	Returns the name of the STB device
sendMessage	message : String	The message is a base64 encoded byte array of the raw CEC bytes. The CEC message includes the device ID for the intended destination.
getCECAddresses	none	return the JSON object <CECAddresses> that is assigned to the local device. It does not contain the <CECAddresses> of other devices on the connected CEC network.
getCECAddresses	none	"CECAddresses" : { "physicalAddress": Array of 4 bytes [byte0, byte1, byte2, byte3], "logicalAddresses" : Array of <CECLogicalAddress> } "CECLogicalAddress" : { "deviceType" : <string> "logicalAddress": <integer> } The deviceType returned is part or all of devices types optionally set by XRE. A CEC device can have multiple deviceTypes, if so an array of <CECLogicalAddress> with size more than one is returned. Default deviceType is Tuner, and its logical Address is either 3, 6, 7, or 10. In messages sent by XRE, XRE can only use the logicalAddress returned from CECAddresses. Accepted deviceType are: "Tuner", "Record", "Playback", "AudioSystem", "VideoProcessor", "Switch"

Events

Name	Content	Description
onMessage	message : String	Fired when a message is sent from an HDMI device. Message is a base64 encoded byte array of the raw CEC bytes.
cecAddressesChanged	JSON object <CECAddresses>	Notify that address of the host CEC device has changed