https://etwiki.sys.comcast.net/display/CE/%5bShared%5d+HDMI-CEC

https://rdkwiki.com/rdk/display/RDK/HDMI+Input

https://www.teamccp.com/confluence/display/CPE/RDK+HDMI+Input+Architecture

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

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

Application API Specification

Overall the RDK-CEC library offers 3 categories of application APIs,

HDMI-CEC Connection

• The Connection APIs allows application to transmit and receive raw data bytes (a.k.a. CEC Frame) that conforms to the HDMI-CEC specification. 
• This is the only interface that the application can use to access CEC Bus.

HDMI-CEC Message and Frame Structure

• The Messages APIs allows application to encode high-level message constructs into CECFrame raw bytes, or decode CECFrame raw bytes into high-level message constructs.

HDMI-CEC Library Interface

• The Library APIs allows application to contrl how the CEC stack operates, such as adding logical address to the stack.

The Host interface allows libCEC implementation to interact with the host environment. Such interaction includes monitoring of the Power State change, the HDMI HotPlug events, or API to change the Host State. The Host Interface is delivered as a run-time plugin to the libCEC stack. This allows the CEC stack to run in any devices that implements the Host Interface.

The Driver Component access the HDMI-CEC SoC Driver via the CEC HAL API. The vendors are responsible in delivering a SoC Driver that conforms to the HAL API (see the header file hdmi_cec_driver.h)

HDMI-CEC Applications

The relation between Application, Connection and CEC-Bus is described in the figure.

CEC Daemon

• This daemon receives Raw Bytes from the SoC Driver and dispatches them into IARM Bus via CecIARMMgr, it also receives Raw Bytes from IARM Bus and send to the SoC Driver. It controls the only access point to the physical HDMI CEC Bus.

Receiver

• This application receives Raw Bytes from IARM Bus and dispatch to Service Manager (which in turn may dispatch the bytes to Guide Application). It also receives Raw bytes from Service Manager and send to the IARM-Bus.

CECDevMgr

• This application is a "sniffer" on the CEC Bus. It monitors all messages on the bus and construct a Device Map, which depicts the topology of all connected devices on the CEC Bus. Other applications can be developed similar to Receiver or CECDevMgr where the CEC Raw bytes (in form of CECFrame) are send/receive to/from IARM Bus. This pseudo CEC Driver implemented on IARM Bus is called CEC IARM Adapter in the diagram.

Methods

"CECAddresses" : {
 "physicalAddress": Array of 4 bytes [byte0, byte1, byte2, byte3],
 "logicalAddresses" : Array of <CECLogicalAddress>
}

"CECLogicalAddress" : {
 "deviceType" : <string> 
 "logicalAddress": <integer>
}

Events