Detailed Summary of SignalK Alarm Management with Node-RED

This project describes how to manage and display alarms generated by the SignalK system in a nautical environment, using Node-RED as the central platform for processing notifications. The solution includes visualization on an old Android tablet and sound alerts for critical alarms.

1. System Objective

The main objective is:

• Receive notifications from SignalK.
• Process them to determine their severity (normal, warning, alarm, emergency).
• Display them on a graphical interface on an Android tablet.
• Emit specific sounds based on the type of alarm.
• Allow the user to mark notifications as "read" or "resolved."

2. Main Components

2.1. Hardware

• Android Tablet: Used as a user interface to display notifications and allow interaction.
• Raspberry Pi (optional): Can be the device running Node-RED if no remote server is used.

2.2. Software

• SignalK: Monitoring system used to generate and send notifications based on boat data (voltage, temperature, etc.).
• Node-RED: Visual programming platform for processing and managing notifications.
• Node-RED Dashboard 2.0: For creating interactive graphical interfaces.
• Plugin PlaySound: To play audio files as alerts.
• Festival TTS: To read messages aloud (if installed on the system).

3. Workflow

3.1. Notification Reception

signalk-notification Node:

• This node receives all notifications generated by SignalK.
• Notifications can have different states: normal, alert, warn, alarm, emergency.

Subflow Manage Notification Array:

• This subflow manages a global array (flow.matrizNotificaciones) where active notifications are stored.
• If a notification already exists in the array, it is updated. If it is new, it is added.
• If a notification changes to a normal state, it is removed from the array.

3.2. Notification Processing

3.2.1. State Filtering

A switch node filters notifications based on their state:

• Non-normal state: Processed to emit sounds and display them on the interface.
• Normal state: Only updated in the notification list and removed from the array.

3.2.2. Sound Emission

The subflow Emit Appropriate Sound or Stop handles sound playback based on the type of alarm:

• Alert: Plays a soft sound.
• Warning: Plays a moderate sound.
• Alarm: Plays a loud sound.
• Emergency: Plays a critical sound.
• Stop: Stops all active sounds.

3.2.3. Voice Reading

An exec node uses the command festival --tts to read the notification message aloud.
This ensures the operator stays informed even if they are not looking at the screen.

3.3. Visualization on the Tablet

3.3.1. Notification Table

A ui-table node displays a list of up to 25 recent notifications.
Each row includes:

• Path: Unique identifier for the notification.
• Description: Message associated with the notification.
• Status: Visual indicator showing whether the notification has been read.

3.3.2. Pop-Up Notifications

A ui-notification node displays pop-up notifications when a new alarm arrives.
The user can interact with these notifications:

• Button "Received": Confirms the notification has been seen.
• Button "Resolved": Changes the notification status to normal and removes it from the array.

3.4. Updating Status in SignalK

When the user marks a notification as "read" or "resolved":

• A signal is sent to the signalk-send-notification node to update the status in SignalK.
• The notification is removed from the global array (flow.matrizNotificaciones).

4. Detailed Implementation

4.1. Initial Setup

Install Node-RED:

• Ensure Node-RED is installed on your Raspberry Pi or server.
• Install necessary packages: node-red-dashboard, node-red-contrib-play-sound, etc.

Configure SignalK:

• Set up SignalK to generate notifications based on your sensors (e.g., average battery voltage).

Prepare the Tablet:

• Install the Node-RED Dashboard app on the Android tablet.
• Connect the tablet to the same WiFi network as the Node-RED server.

4.2. Node-RED Flow

4.2.1. signalk-notification Node

• Configure this node to receive all notifications from SignalK.
• Define rules to filter specific notifications if needed.

4.2.2. Subflow Manage Notification Array

• Create a subflow to manage the global notification array.
• Use function nodes to:
  • Create or update the array.
  • Remove resolved notifications.

4.2.3. Subflow Emit Appropriate Sound or Stop

• Create a subflow to play sounds based on the type of alarm.
• Use PlaySound nodes to load specific audio files.

4.2.4. ui-table Node

• Configure this node to display the notification table.
• Customize columns to show relevant information (path, description, status).

4.2.5. ui-notification Node

• Configure this node to display pop-up notifications.
• Add buttons for user interaction:
  • "Received": Confirms the notification.
  • "Resolved": Resolves the notification.

4.2.6. exec Node

• Configure this node to use festival --tts and read messages aloud.
• Ensure the system has Festival installed and configured with Spanish support.

4.3. Optimization

Debounce for Repetitions:

• Implement a debounce mechanism to avoid annoying repeated alarms.
• Allow normal-state notifications to pass through without applying debounce.

Automatic Cleanup:

• Schedule automatic removal of old entries from the global array to keep it clean.

5. Expected Results

• Clear Visualization: All notifications are displayed on an intuitive interface on the tablet.
• Custom Sounds: Each alarm type has a specific sound for easy identification.
• Simple Interaction: Users can mark notifications as read or resolved with a single click.
• Real-Time Updates: Notifications are automatically updated in SignalK and on the tablet interface.

6. Conclusions

This system provides a robust and customizable solution for managing alarms in a nautical environment. By combining SignalK with Node-RED, a seamless integration between sensors, notifications, and user interfaces is achieved. Using an old Android tablet as the interface adds value to the project by repurposing a device that would otherwise be inactive.