How to use the Piano Ui Class

The PianoUI class is a hybrid Qt-ROS 2 node that provides the graphical interface for MIDI-to-UR3 playback. It handles file conversion, playback state management, and real-time camera visualization.

How to Initialize the UI Node

In your main execution file (typically main.cpp), instantiate the class and add it to a ROS 2 executor to handle service calls and image subscriptions.

1. <strong>Initialize ROS 2</strong>

rclcpp::init(argc, argv);

2. <strong>Instantiate the UI</strong>

auto ui_node = std::make_shared<UI::PianoUI>();

3. <strong>Show the window and spin the node</strong>

ui_node->show();
rclcpp::spin(ui_node);

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How to Interact with the UI Features

Step 1: Processing a New MIDI File

• Action: Click the "Select A MIDI File" button.
• Result: This opens a file dialog.
• Logic: Selecting a .mid file triggers the MidiProcessor to convert it to a .mipi file.
• Storage: Processed files are automatically saved to ~/mipi_files/.

Step 2: Loading an Existing .mipi File

• Action: Use the Dropdown Menu (QComboBox).
• Scanning: This scans the ~/mipi_files/ directory.
• Automation: Selecting a file automatically populates the Channel Selector with the instruments found in that file.

Step 3: Selecting a Channel

• Action: Click a Radio Button in the Channel Selector.
• Communication: This immediately sends a /MIPI/load service request to the robot.
• Payload: It passes the .mipi filepath and the specific MIDI channel index.

Step 4: Controlling Playback

Use the playback buttons to communicate with the robot via the /MIPI/play_pause and /MIPI/direction services.

• Play/Pause Button: Toggles the robot movement state.
• Direction Toggle: Toggles between Forward (⏩) and Reverse (⏪).
• Speed Slider: Adjusts the Time Scale (0.01 to 1.0) via the /MIPI/time_scale service.

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Technical Interface Reference

Service Clients Used

The UI communicates with the robot backend using these specific service calls:

 // Sends a play or pause signal
 playback_client = this->create_client<jamc::srv::Func>("/MIPI/play_pause");
 
 // Sends a signal to reverse or go forward
 direction_client = this->create_client<jamc::srv::Func>("/MIPI/direction");
 
 // Sends a double (0.0 to 1.0) to scale robot speed
 time_scale_client = this->create_client<jamc::srv::TimeScale>("/MIPI/time_scale");
 
// Sends the filename and channel index to load onto the robot
channel_client = this->create_client<jamc::srv::Load>("/MIPI/load");

Camera Subscription

The UI displays a live feed by subscribing to the following topic:

• Topic: /camera/camera/color/image_raw
• Message Type: sensor_msgs::msg::Image