cec-client-mqtt-bridge

HDMI CEC-MQTT Bridge using the cec-client binary

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Description

This lets you send commands and receive answers from the cec-client binary through MQTT.

• To send commands to cec-client you publish into cec/client/tx
• To listen for cec-client output you subscribe to cec/client/rx/TRAFFIC

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Why this exists

All the existing implementations try to connect directly to CEC and interpret the messages although this is already done in cec-client and it's the most reliable implementation. Everyone checks the CEC functionality and/or their implementation with cec-client anyway.

So this project is creating a bridge between the cec-client binary and an MQTT broker placed on localhost. Basically it's creating a dual-way pipe between the services.

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How's this working

• The cec-client-mqtt-bridge binary connects to the MQTT broker
• It subscribes to cec/client/tx on a different thread
• It spills the received messages in stdout which is piped to cec-client
• It then listens for stdin input which is piped from cec-client on the main thread
• When receiving something it publishes the message on cec/client/rx/TRAFFIC

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Hardware

Make sure you have HDMI CEC capable hardware

• Raspberry PIs have this by default
• Intel NUCs usually require an additional hardware module to be installed
• Other devices can use this generic adapter

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Build

The build/dependency/run scripts are built for Apline Linux but can be easily adapted for Debian or something else.

# Install git, go & musl-dev
ash install-build-dependencies.sh

# Build binary
ash build.sh

# Remove git, go & musl-dev
ash remove-build-dependencies.sh

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Runtime dependencies

For this to work you need the cec-client binary.

To install it in Alpine Linux just run:

apk add libcec

For Debian based systems this should do the trick:

apt install cec-utils

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Run

Creates two pipes in /tmp/fifo/ which will facilitate the communication between processes and then launches the processes.

bash run.sh

Here's how run.sh looks like:

# Create pipes
mkdir -p /tmp/fifo
rm -rf /tmp/fifo/mqtt2cec /tmp/fifo/cec2mqtt
mkfifo /tmp/fifo/mqtt2cec /tmp/fifo/cec2mqtt

# Launch bridge
./cec-client-mqtt-bridge > /tmp/fifo/mqtt2cec < /tmp/fifo/cec2mqtt &

# Launch cec client
cec-client < /tmp/fifo/mqtt2cec > /tmp/fifo/cec2mqtt

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Docker

To use this in an Alpine based Docker image you could use this:

ENV CECCLIENT_MQTT_BRIDGE_PATH "/app/modules/cec-client-mqtt-bridge"
RUN echo -e "\n > INSTALL CEC-CLIENT-MQTT-BRIDGE\n" \
 && apk add --no-cache --virtual=build-dependencies \
    git \
    \
 && mkdir -p $CECCLIENT_MQTT_BRIDGE_PATH/src \
 && cd $CECCLIENT_MQTT_BRIDGE_PATH \
 && git clone https://github.com/blchinezu/cec-client-mqtt-bridge.git ./src \
 && ash src/install-build-dependencies.sh \
 && ash src/build.sh \
 \
 && echo -e "\n > CLEANUP\n" \
 && ash src/remove-build-dependencies.sh \
 && apk del --purge build-dependencies \
 && rm -rf \
    ./src \
    /root/.cache \
    /root/go \
    /tmp/* \
    /var/tmp/*