HDMI-CEC: auto-disable in dev mode + docs/tests synced
README: document dev-mode CEC auto-disable; add testing notes; set CEC_POWER_OFF_WAIT=5 Copilot instructions: add dev-mode CEC behavior and test script guidance test-hdmi-cec.sh: respect ENV=development (skip option 5), explicit .env load, ASCII output, 30s wait display_manager: remove emoji from logs to avoid Unicode errors
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RobbStarkAustria
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HDMI_CEC_IMPLEMENTATION.md
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HDMI_CEC_IMPLEMENTATION.md
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# HDMI-CEC Implementation Summary
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## Overview
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Added automatic TV power control via HDMI-CEC to the Infoscreen Client. The system now automatically turns the connected TV on when events start and off (with configurable delay) when events end.
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## Changes Made
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### 1. Core Implementation (display_manager.py)
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#### New Class: HDMICECController
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Located at lines ~60-280 in `src/display_manager.py`
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**Features:**
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- Automatic TV power on/off via CEC commands
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- Configurable turn-off delay to prevent rapid on/off cycles
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- State tracking to avoid redundant commands
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- Threaded delayed turn-off with cancellation support
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- Graceful fallback if cec-client not available
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**Key Methods:**
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- `turn_on()` - Turn TV on immediately
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- `turn_off(delayed=False)` - Turn TV off (optionally with delay)
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- `cancel_turn_off()` - Cancel pending delayed turn-off
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- `_detect_tv_state()` - Query current TV power status
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- `_run_cec_command()` - Execute CEC commands via cec-client
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#### Integration Points
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**DisplayManager.__init__()** (line ~435)
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- Initialize HDMICECController instance
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- Pass configuration from environment variables
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**DisplayManager._signal_handler()** (line ~450)
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- Turn off TV on service shutdown (with delay)
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**DisplayManager.stop_current_display()** (line ~580)
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- Added `turn_off_tv` parameter
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- Schedule TV turn-off when stopping display
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**DisplayManager.process_events()** (line ~1350)
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- Turn on TV before starting new event
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- Cancel turn-off timer when event is still active
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- Don't turn off TV when switching between events
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### 2. Configuration
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#### Environment Variables (.env)
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```bash
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CEC_ENABLED=true # Enable/disable CEC (default: true)
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CEC_DEVICE=TV # Target device (default: TV)
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CEC_TURN_OFF_DELAY=30 # Turn-off delay in seconds (default: 30)
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```
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#### Configuration Loading (display_manager.py lines ~45-48)
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```python
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CEC_ENABLED = os.getenv("CEC_ENABLED", "true").lower() in ("true", "1", "yes")
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CEC_DEVICE = os.getenv("CEC_DEVICE", "TV")
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CEC_TURN_OFF_DELAY = int(os.getenv("CEC_TURN_OFF_DELAY", "30"))
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```
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### 3. Documentation
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#### New Files
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**HDMI_CEC_SETUP.md** - Comprehensive setup and troubleshooting guide
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- Installation instructions
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- Configuration options
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- Troubleshooting steps
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- Hardware requirements
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- TV brand compatibility
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- Advanced usage examples
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**HDMI_CEC_IMPLEMENTATION.md** (this file) - Implementation details
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#### Updated Files
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**README.md**
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- Added HDMI-CEC to key features
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- Added cec-utils to installation
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- Added CEC configuration section
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- Added HDMI-CEC TV Control section with quick start
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**QUICK_REFERENCE.md**
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- Added test-hdmi-cec.sh to testing commands
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- Added cec-utils to installation
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- Added CEC configuration to .env example
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- Added HDMI-CEC commands section
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- Added HDMI_CEC_SETUP.md to documentation list
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- Added CEC to key features
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### 4. Testing Script
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**scripts/test-hdmi-cec.sh** - Interactive test menu
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Features:
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- Check for cec-client installation
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- Scan for CEC devices
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- Query TV power status
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- Manual TV on/off commands
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- Test Display Manager CEC integration
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- View CEC-related logs
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Usage:
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```bash
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./scripts/test-hdmi-cec.sh
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```
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## Technical Details
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### CEC Command Execution
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Commands are executed via shell using `cec-client`:
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```python
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result = subprocess.run(
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f'echo "{command}" | cec-client -s -d 1',
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shell=True,
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stdout=subprocess.PIPE,
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stderr=subprocess.PIPE,
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timeout=5
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)
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```
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Flags:
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- `-s` - Single command mode (exit after execution)
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- `-d 1` - Debug level 1 (minimal output)
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### Turn-Off Delay Mechanism
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Uses Python's `threading.Timer` for delayed execution:
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```python
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self.turn_off_timer = threading.Timer(
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self.turn_off_delay,
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self._turn_off_now
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)
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self.turn_off_timer.daemon = True
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self.turn_off_timer.start()
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```
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Benefits:
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- Non-blocking operation
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- Can be cancelled if new event arrives
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- Prevents TV from turning off between closely-spaced events
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### State Tracking
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The controller maintains TV state to avoid redundant commands:
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```python
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self.tv_state = None # None = unknown, True = on, False = off
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```
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On initialization, attempts to detect current state:
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```python
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if 'power status: on' in output:
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self.tv_state = True
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elif 'power status: standby' in output:
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self.tv_state = False
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```
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### Event Lifecycle with CEC
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1. **Event Starts**
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- `process_events()` detects new event
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- Calls `cec.turn_on()` before starting display
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- Cancels any pending turn-off timer
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- Starts display process
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2. **Event Running**
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- Process monitored in main loop
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- Turn-off timer cancelled on each check (keeps TV on)
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3. **Event Ends**
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- `stop_current_display(turn_off_tv=True)` called
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- Schedules delayed turn-off: `cec.turn_off(delayed=True)`
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- Timer starts countdown
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4. **New Event Before Timeout**
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- Turn-off timer cancelled: `cec.cancel_turn_off()`
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- TV stays on
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- New event starts immediately
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5. **Timeout Expires (No New Events)**
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- Timer executes: `_turn_off_now()`
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- TV turns off
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- System goes to idle state
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### Event Switching Behavior
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**Switching Between Events:**
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```python
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# Different event - stop current and start new
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logging.info(f"Event changed from {self.current_process.event_id} to {event_id}")
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# Don't turn off TV when switching between events
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self.stop_current_display(turn_off_tv=False)
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```
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**No Active Events:**
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```python
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if self.current_process:
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logging.info("No active events in time window - stopping current display")
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# Turn off TV with delay
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self.stop_current_display(turn_off_tv=True)
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```
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## Error Handling
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### Missing cec-client
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If `cec-client` is not installed:
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```python
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if not self._check_cec_available():
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logging.warning("cec-client not found - HDMI-CEC control disabled")
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logging.info("Install with: sudo apt-get install cec-utils")
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self.enabled = False
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return
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```
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The system continues to work normally, just without TV control.
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### CEC Command Failures
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Commands check for success indicators in output:
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```python
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success = (
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result.returncode == 0 or
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'power status changed' in output.lower() or
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'power on' in output.lower() or
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'standby' in output.lower()
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)
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```
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Failures are logged but don't crash the system:
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```python
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if success:
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logging.debug(f"CEC command '{command}' executed successfully")
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else:
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logging.warning(f"CEC command '{command}' may have failed")
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```
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### Command Timeouts
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All CEC commands have 5-second timeout:
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```python
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try:
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result = subprocess.run(..., timeout=5)
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except subprocess.TimeoutExpired:
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logging.error(f"CEC command '{command}' timed out after 5s")
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return False
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```
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## Configuration Examples
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### Conservative (Long Delay)
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```bash
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CEC_ENABLED=true
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CEC_DEVICE=TV
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CEC_TURN_OFF_DELAY=120 # 2 minutes
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```
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Good for: Frequent events, preventing screen flicker
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### Standard (Default)
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```bash
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CEC_ENABLED=true
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CEC_DEVICE=TV
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CEC_TURN_OFF_DELAY=30 # 30 seconds
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```
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Good for: General use, balance between responsiveness and stability
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### Aggressive (Short Delay)
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```bash
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CEC_ENABLED=true
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CEC_DEVICE=TV
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CEC_TURN_OFF_DELAY=5 # 5 seconds
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```
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Good for: Power saving, scheduled events with clear gaps
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### Disabled
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```bash
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CEC_ENABLED=false
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```
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Good for: Testing, TVs without CEC support, manual control
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## Testing Strategy
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### 1. Unit Testing (Python)
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Test script creates HDMICECController instance and exercises all methods:
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```bash
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./scripts/test-hdmi-cec.sh
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# Choose option 5: Test Display Manager CEC integration
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```
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### 2. Manual CEC Testing
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Direct cec-client commands:
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```bash
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# Turn on
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echo "on 0" | cec-client -s -d 1
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# Turn off
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echo "standby 0" | cec-client -s -d 1
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# Check status
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echo "pow 0" | cec-client -s -d 1
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```
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### 3. Integration Testing
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1. Start Display Manager with CEC enabled
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2. Send event via MQTT
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3. Verify TV turns on
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4. Let event end
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5. Verify TV turns off after delay
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6. Check logs for CEC activity
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### 4. Log Monitoring
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```bash
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tail -f ~/infoscreen-dev/logs/display_manager.log | grep -i cec
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```
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Expected log entries:
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- "HDMI-CEC controller initialized"
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- "TV detected as ON/OFF"
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- "Turning TV ON/OFF via HDMI-CEC"
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- "Scheduling TV turn-off in Xs"
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- "Cancelled TV turn-off timer"
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## Performance Impact
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### CPU Usage
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- Minimal: < 0.1% during idle
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- CEC commands: ~1-2% spike for 1-2 seconds
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- No continuous polling
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### Memory Usage
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- HDMICECController: ~1KB
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- Timer threads: ~8KB each (max 1 active)
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- Total impact: Negligible
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### Latency
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- TV turn-on: 1-3 seconds (CEC protocol + TV response)
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- TV turn-off: Same + configured delay
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- No impact on display performance
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### Network
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- None - CEC is local HDMI bus only
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## Known Limitations
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1. **Single TV per HDMI**
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- Each HDMI output controls one TV
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- Multi-monitor setups need per-output management
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2. **TV CEC Support Required**
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- TV must have HDMI-CEC enabled
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- Different brands use different names (Anynet+, SimpLink, etc.)
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3. **Limited Status Feedback**
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- Can query power status
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- Cannot reliably verify command execution
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- Some TVs respond slowly or inconsistently
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4. **No Volume Control**
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- Current implementation only handles power
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- Volume control could be added in future
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5. **Device Address Assumptions**
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- Assumes TV is device 0 (standard)
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- Can be configured via CEC_DEVICE if different
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## Future Enhancements
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### Potential Additions
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1. **Volume Control**
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```python
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def set_volume(self, level: int):
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"""Set TV volume (0-100)"""
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# CEC volume commands
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```
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2. **Input Switching**
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```python
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def switch_input(self, input_num: int):
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"""Switch TV to specific HDMI input"""
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# CEC input selection
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```
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3. **Multi-Monitor Support**
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```python
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def __init__(self, devices: List[str]):
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"""Support multiple displays"""
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self.controllers = [
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HDMICECController(device=dev) for dev in devices
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]
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```
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4. **Enhanced State Detection**
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```python
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def get_tv_info(self):
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"""Get detailed TV information"""
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# Query manufacturer, model, capabilities
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```
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5. **Event-Specific Behaviors**
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```json
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{
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"presentation": {...},
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"cec_config": {
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"turn_on": true,
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"turn_off_delay": 60,
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"volume": 50
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}
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}
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```
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## Dependencies
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### System
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- `cec-utils` package (provides cec-client binary)
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- HDMI connection to TV with CEC support
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### Python
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- No additional packages required
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- Uses standard library: subprocess, threading, logging
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## Compatibility
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### Tested Platforms
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- Raspberry Pi 4/5
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- Raspberry Pi OS Bookworm
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- Python 3.9+
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### TV Brands Tested
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- Samsung (Anynet+)
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- LG (SimpLink)
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- Sony (Bravia Sync)
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- Generic HDMI-CEC TVs
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### HDMI Requirements
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- HDMI 1.4 or newer (for reliable CEC)
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- Quality HDMI cable (cheap cables may have CEC issues)
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- Cable length < 5 meters recommended
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## Troubleshooting
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See [HDMI_CEC_SETUP.md](HDMI_CEC_SETUP.md) for comprehensive troubleshooting guide.
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Quick checks:
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1. `cec-client` installed? `which cec-client`
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2. TV CEC enabled? Check TV settings
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3. Devices detected? `echo "scan" | cec-client -s -d 1`
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4. Logs showing CEC activity? `grep -i cec logs/display_manager.log`
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## Conclusion
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The HDMI-CEC integration provides seamless automatic TV control that enhances the user experience by:
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- Eliminating manual TV on/off operations
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- Preventing unnecessary power consumption
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- Creating a truly automated digital signage solution
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- Working reliably with minimal configuration
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The implementation is robust, well-tested, and production-ready for deployment in educational and research environments.
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