HDMI CEC~

This feature is experimental and still under development. It has only been tested on ESP8266.

This feature is not included in standard Tasmota builds.

When compiling your build add the following flag to the build environment or user_config_override.h:

#define USE_HDMI_CEC

What is HDMI CEC?~

HDMI CEC is a feature of HDMI designed to control HDMI connected devices by using only one remote controller; so, individual CEC enabled devices can command and control each other without user intervention, for up to 15 devices.

This features enables a simple Tasmota device plugged to any HDMI port of your home equipment, to control the TV and other equipments, with a protocol more standard and robust than Infra-Red.

Hardware needed~

HDMI CEC needs only 3 GPIOs to be connected to an HDMI port. You can use a simple ESP8266 Wemos D1 Mini plugged with Dupont cables to an HDMI pass-through like these devices from Alix

The GPIOs from ESP devices are electrically compatible with HDMI specifications, so you can simply connect GPIOs with no additional harware components:

HDMI_CEC_template

Wemos D1 Mini	Configuration	HDMI
GPIO 2	HDMI CEC	HDMI Pin 13 GPIO 2 on Wemos D1 Mini is connected to a blue Led which is a visual indicator of CEC traffic
GPIO 4	I2C SDA	HDMI Pin 16
GPIO 5	I2C SCL	HDMI Pin 15
Ground		HDMI Pin 17
+5V		HDMI Pin 18 If another device is present on the same HDMI port, it provides +5V with enough power for ESP8266. In such case you don't need an external power (tested with AppleTV).

Below is the template:

Template {"NAME":"HDMI CEC","GPIO":[1,1,9824,1,640,608,1,1,1,1,1,1,1,1],"FLAG":0,"BASE":18}

Quick start and quick tour~

HDMI CEC auto-detects all parameters and does not need specific configuration, although you may override the default configuration if needed. By default, Tasmota announces itself as a "Playback Device" on the HDMI bus.

Logs during boot:

00:00:00.002 HDW: ESP8266EX
00:00:00.005 UFS: FlashFS mounted with 1992 kB free
00:00:00.063 CFG: Loaded from File, Count 422
00:00:00.118 QPC: Reset
00:00:00.130 Project tasmota - Tasmota Version 13.1.0.2(tasmota-4M)-2_7_4_9(2023-09-01T20:20:26)
00:00:00.247 CEC: HDMI CEC initialized on GPIO 2, Logical address 8, Physical address 0x1000

Extra logs when Weblog 3:

00:00:00.001 HDW: ESP8266EX
00:00:00.007 UFS: FlashFS mounted with 1992 kB free
00:00:00.066 CFG: Loaded from File, Count 426
00:00:00.072 QPC: Count 1
00:00:00.074 CFG: CR 342/699, Busy 0
00:00:00.082 SRC: Restart
00:00:00.083 Project tasmota - Tasmota Version 13.1.0.2(tasmota-4M)-2_7_4_9(2023-09-01T20:20:26)
00:00:00.084 CEC: trying to read physical address
00:00:00.110 CEC: successfully read EDID 256 bytes, extensions count 1
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
00:00:00.111 CEC: physical address found: 0x1000
00:00:00.152 CEC: Packet sent: 44 ACK
00:00:00.199 CEC: Packet sent: 88 NAK
00:00:00.200 CEC: HDMI CEC initialized on GPIO 2, Logical address 8, Physical address 0x1000
00:00:00.678 CEC: Packet sent: 8F84100004 ACK

In the above example, the first part probes I2C to get EDID data and compute the physical address. Tasmota sends 44 message to check if Logical address 4 is in use. Since the message is ACKed it is in use (here by an AppleTV plugged on the same HDMI port). It tries address 8 with packet 88. NAK indicates that the address is free, so it is claimed by Tasmota. The message 8F84100004 indicates to the bus that logical device 8 has the physical address 0x1000, i.e. connected the HDMI port 1 of TV.

Commands~

Command Parameters

HdmiType : set the CEC device type (0..15 as per CEC specs)
The default value is 4 (Playback Device). Changes require a restart to renegociate a new HDMI logical address.
Possible values are:
0: TV
1: Recording Device
2: Reserved
3: Tuner
4: Playback Device
5: Audio System

HdmiSend Send a payload to the TV or to any device
HdmiSend <hex>: sends the <hex> payload to the TV
HdmiSend { ["To": <to>, ] "Data":"<hex>"} gives more control about the target.
<to> is the logical address of the targer, default is 0 which is the TV
<hex> is the payload
Examples:
HdmiSend 8F or HdmiSend {"Data":"8F"} - ask the power status of the TV
HdmiSend {"To":4,"Data":"8C} - ask its vendor id to logical address 4

Receiving and parsing payloads~

Currently payloads are passed as HEX data without any encoding/decoding.

Whenever a message is received on the CEC bus, a payload using the following syntax is triggered and can be matched with a Rule. Only messages addressed to Tasmota are published as payloads in MQTT, all messages not adressed to Tasmota are masked to avoid generating too much traffic. Note: the total traffic can be monitored with loglevel 3.

Received payloads generate an Rule event as follows:

{"HdmiReceived":{"From":<from>,"To":<to>,"Data":"<hex>"}}

Example: command HdmiSend 8F

20:07:59.449 CMD: HdmiSend 8F
20:07:59.454 RSL: RESULT = {"HdmiSend":"Done"}
20:07:59.632 RSL: SENSOR = {"HdmiReceived":{"From":0,"To":8,"Data":"9001"}}

In the above, Tasmota sends command 8F (Give Device Power Status) to query the power status of the TV. The response 9001 (Report Power Status) indicates that the TV is in Standby mode.

Turning the TV on~

Command: HdmiSend 04

Turning the TV on~

Command: HdmiSend 36

Advanced usage~

When setting loglevel 3 (ex: WebLog 3), you see all messages being published in the CEC bus. They all generate an internal JSON event HdmiReceived that can be used by a rule.

The following commands are for advanced users or specific use-cases:

Command	Parameters
HdmiSendRaw	`<hex>`: send a raw payload to the HDMI CEC bus This gives full control over messages and allows to impersonate another device `HdmiSendRaw 408F` pretend that device at logical address `4` asks TV for its power status.
HdmiAddr	: set the default HDMI Physical Address in case it cannot be discovered. The default value is `0x1000` which is HDMI Port 1 on the TV This value is only used if the I2C port is not connected or if the discovery failes. If no argumant, this command returns the current physical adress.

The CEC-O-MATIC tool is handy to decode and encode payloads.