Diagnostic Bridge Configuration

The ros2_medkit_diagnostic_bridge node converts standard ROS 2 /diagnostics messages to fault events, providing a migration path for existing diagnostic infrastructure.

Overview 

The diagnostic bridge:

Subscribes to /diagnostics (or custom topic)
Maps DiagnosticStatus names to fault codes
Reports faults to the FaultManager via ReportFault service

Status Mapping:

Diagnostic Level	Fault Event	Severity
OK	PASSED	(healing event)
WARN	FAILED	SEVERITY_WARN (1)
ERROR	FAILED	SEVERITY_ERROR (2)
STALE	FAILED	SEVERITY_ERROR (2)

Parameters 

diagnostic_bridge:
  ros__parameters:
    diagnostics_topic: "/diagnostics"   # Topic to subscribe to
    auto_generate_codes: true           # Auto-generate fault codes from names

Parameter	Default	Description
`diagnostics_topic`	`/diagnostics`	Topic to subscribe for `DiagnosticArray` messages.
`auto_generate_codes`	`true`	Automatically generate fault codes from diagnostic names when no explicit mapping exists.

Custom Fault Code Mappings 

Map specific diagnostic names to custom fault codes using the name_to_code parameter prefix:

diagnostic_bridge:
  ros__parameters:
    diagnostics_topic: "/diagnostics"
    auto_generate_codes: true
    name_to_code:
      motor_temp: "MOTOR_OVERHEAT"
      battery_level: "LOW_BATTERY"
      camera_driver: "CAMERA_FAILURE"

Or via command line:

ros2 run ros2_medkit_diagnostic_bridge diagnostic_bridge \
  --ros-args \
  -p "name_to_code.motor_temp:=MOTOR_OVERHEAT" \
  -p "name_to_code.battery_level:=LOW_BATTERY"

Auto-Generated Fault Codes 

When auto_generate_codes: true and no explicit mapping exists, fault codes are generated from the diagnostic name:

Convert to uppercase
Replace spaces, slashes, and dashes with underscores
Remove non-alphanumeric characters (except underscore)
Prepend DIAG_ prefix

Examples:

Diagnostic Name	Generated Fault Code
`motor_temp`	`DIAG_MOTOR_TEMP`
`/camera/driver`	`DIAG_CAMERA_DRIVER`
`Battery Level Monitor`	`DIAG_BATTERY_LEVEL_MONITOR`

Launch File Configuration 

Example launch file:

from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    return LaunchDescription([
        Node(
            package='ros2_medkit_diagnostic_bridge',
            executable='diagnostic_bridge_node',
            name='diagnostic_bridge',
            parameters=[{
                'diagnostics_topic': '/diagnostics',
                'auto_generate_codes': True,
                'name_to_code': {
                    'motor_temp': 'MOTOR_OVERHEAT',
                    'battery_level': 'LOW_BATTERY',
                }
            }],
        ),
    ])

Integration with FaultManager 

The diagnostic bridge requires a running FaultManager to report faults. Ensure the FaultManager is started before the bridge:

# Terminal 1: Start FaultManager
ros2 run ros2_medkit_fault_manager fault_manager_node

# Terminal 2: Start Diagnostic Bridge
ros2 run ros2_medkit_diagnostic_bridge diagnostic_bridge_node

Or use a combined launch file:

from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    return LaunchDescription([
        Node(
            package='ros2_medkit_fault_manager',
            executable='fault_manager_node',
            name='fault_manager',
        ),
        Node(
            package='ros2_medkit_diagnostic_bridge',
            executable='diagnostic_bridge_node',
            name='diagnostic_bridge',
        ),
    ])

Migration Strategy 

For transitioning from standard ROS 2 diagnostics to direct fault reporting:

Phase 1: Deploy diagnostic bridge alongside existing diagnostics infrastructure
Phase 2: Create explicit mappings for important diagnostics
Phase 3: Migrate critical nodes to direct FaultReporter usage
Phase 4: Disable auto_generate_codes, rely only on explicit mappings
Phase 5: Remove diagnostic bridge when all nodes use FaultReporter