Jazzy version of changes to support present temperature, current, voltage, and load

[bueche]

his PR is meant to address Issue #104 by enabling the ros2 /dynamixel_hardware_interface/dxl_state state to return servo values of "Present Temperature", "Present Input Voltage", "Present Current", and/or "Present Load". Some servo's return "Present Current" (XL330's) while others "Present Load" (e.g., XL430's). Whether or not they return these depends on the model files.

This PR is for the jazzy version (a separate PR was created for the humble branch). This has been tested in an environment in which both XL330's and XL430's are present to confirm that the Present current is always zero for XL430's and Present Load is always zero for XL330s. This is shown below with the slightly annotated output. In this example id's 1 & 2 are XL430's and id's 3 - 6 are XL330's.

The return values are not adjusted in any way, the consumer will need to do so (e.g., convert the Present Load from its raw value by dividing by 10 .. to change 146 to 14.6% and to divide by 10 do adjust the voltage values 121 becomes 12.1 v.

Example use:

$ ros2 topic echo /dynamixel_hardware_interface/dxl_state --once
header:
  stamp:
    sec: 1770579229
    nanosec: 459868213
  frame_id: ''
comm_state: 0
id:
- 1
- 2
- 3
- 4
- 5
- 6
torque_state:
- false
- false
- false
- false
- false
- false
dxl_hw_state:
- 0
- 0
- 0
- 0
- 0
- 0
present_temperature:
- 32
- 41
- 21
- 20
- 20
- 23
present_input_voltage:
- 121
- 121
- 57
- 56
- 57
- 56
present_current:
- 0  <--- ALWAYS ZERO FOR XL430's
- 0 <--- ALWAYS ZERO FOR XL430's
- -19
- 15
- -12
- 21
present_load:
- 0 
- 146
- 0 <--- ALWAYS ZERO FOR XL330's 
- 0 <--- ALWAYS ZERO FOR XL330's
- 0 <--- ALWAYS ZERO FOR XL330's
- 0 <--- ALWAYS ZERO FOR XL330's
---

[gemini-code-assist]

Summary of Changes

Hello @bueche, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the dynamixel_hardware_interface by integrating support for reading and publishing additional telemetry data from Dynamixel servos. It addresses Issue #104 by enabling the dxl_state ROS2 message to include "Present Temperature", "Present Input Voltage", "Present Current", and "Present Load". The changes involve introducing a flexible mechanism to process these values, including specific scaling factors, and ensuring they are correctly populated for both XL330 and XL430 models, providing more comprehensive servo state information to consumers.

Highlights

• New Telemetry Data Support: Added support for 'Present Temperature', 'Present Input Voltage', 'Present Current', and 'Present Load' telemetry data to the dxl_state ROS2 message, addressing Issue DynamixelState.msg doesn't return temperature, voltage, load, or current #104.
• Flexible Telemetry Processing: Introduced a processTelemetryInterface method to dynamically handle and scale various telemetry data types, ensuring proper conversion before updating the state message fields.
• Message Field Initialization and Population: Ensured that new telemetry fields within the DynamixelHardware class are properly initialized to zero and then populated during the read cycle based on available servo data.

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Changelog

• include/dynamixel_hardware_interface/dynamixel_hardware_interface.hpp
  • Declared processTelemetryInterface method.
• src/dynamixel_hardware_interface.cpp
  • Defined TelemetryInterfaces constants for various telemetry types.
  • Created TelemetryHandler struct to manage scaling and message field assignment.
  • Resized dxl_state_msg_ arrays for new telemetry fields (present_temperature, present_input_voltage, present_current, present_load) during initialization.
  • Implemented processTelemetryInterface to map interface names to their respective handlers, apply scaling, and update the corresponding fields in dxl_state_msg_.
  • Modified the read method to initialize new telemetry fields to zero and then iterate through state interfaces to extract and process telemetry values using processTelemetryInterface.

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[gemini-code-assist]

Code Review

This pull request introduces support for reporting 'Present Temperature', 'Present Input Voltage', 'Present Current', and 'Present Load' from Dynamixel servos, addressing Issue #104. The changes include defining new constants for telemetry interface names, a TelemetryHandler struct for processing, and a processTelemetryInterface method to manage data scaling and message field updates. The on_init and read methods have been appropriately modified to initialize and populate these new telemetry fields. A minor issue was identified regarding the scaling factor for 'Present Load', which could lead to incorrect values being reported in the dxl_state message.

[gemini-code-assist]

The scale_factor for TelemetryInterfaces::LOAD should be 10.0 to match the example output and the description in the pull request body. The description states that the consumer needs to divide by 10 to get the percentage (e.g., 146 -> 14.6%), implying the message should store the raw integer 146. If the value parameter to processTelemetryInterface is already the physical value (e.g., 14.6), then multiplying by 10 will restore the raw integer 146 for storage in dxl_state_msg_.present_load.

Currently, with scale_factor = 1.0, if value is 14.6, converted_value becomes 14, which is a loss of precision and does not match the expected output.

    {TelemetryInterfaces::LOAD,
     {10.0,  // Scale to 0.1% units (e.g., 14.6% -> 146)
      [](DynamixelHardware* hw, int16_t val, size_t idx) {
        hw->dxl_state_msg_.present_load.at(idx) = val;
      }}}