BiDexHand

Budget for the mechanism and its integration

The PWM BOM lists 16 FeeTech FT90M servos, one Servo2040 and a 6 V 5 A supply. It also calls for printed components, precision shoulder screws, bushings, springs, inserts, tendon line and PTFE tubing. Those are part of the mechanism, not incidental extras. The BOM also includes a wrist camera; this review has not established that camera as mandatory for basic direct servo commands. No complete current delivered cost was verified. [S005] [S007]

STEP and STL files establish available design artifacts, not dimensional fit or fabrication success. The README links an external Onshape design and demonstrations; those external models and videos were not inspected as an assembly qualification. Tendon routing, tension and individual joint limits still need a builder-specific check. [S001] [S013]

The quickstart and the preserved launch file differ

The README says ROS 2 Jazzy is the primary tested environment and gives rosdep/colcon build steps. Its direct-control quickstart names multi_servo_control.launch.xml, but the archived package supplies multi_servo.launch.xml and installs that filename in setup.py. This is a source-level mismatch, not a launch command verified by this publication. [S001] [S008] [S009] [S013]

The supplied launch file starts the serial-control node unconditionally and starts it again in streaming mode, using the same USB argument. That needs reconciliation before treating the launch as a ready-to-run recipe. The control node opens its port at 115200 and requires exactly 16 streamed positions, mapped to channels 0–15. A successful serial write is what its service reports; it is not measured joint feedback. [S007] [S008]

Controller capacity does not establish joint travel

The firmware initializes and enables all 18 Servo2040 outputs at startup, while the hand and streaming interface use 16. Its position labels span minus to plus 140, but the implementation maps those values linearly to 1000–2000 microsecond pulses. Those labels do not independently establish the travel of the installed servos or the assembled tendon mechanism. Startup centering is a real commanded behavior in the source and needs consideration before attaching a tensioned mechanism. [S006] [S007]

The ROS node formats positions to three decimal places, while the firmware uses integer parsing before the pulse calculation. Fractional command precision is therefore discarded on this inspected path. This finding comes from reading the two implementations; no board communication or physical positioning accuracy was measured. [S006] [S007]

Calibration and licensing are separate checks

The calibration node uses AprilTag measurement services, with configurable motor and tag mappings. The supplied configuration identifies specific MCP and PIP calibration mappings; it is not evidence that every joint in a newly built hand has already been calibrated. Camera setup, tag geometry, tendon adjustment and a complete whole-hand sequence remain unverified here. [S011] [S012]

The root repository provides MIT terms, while hand_servo_control includes an Apache-2.0 license. Package-level notices must remain part of the software assessment rather than being replaced with the root label. Purchased electronics, the alternative bus-servo route, external VR tracking and Franka integration have separate requirements. This entry covers available sources and concrete setup gaps, not a reproduced dexterity or teleoperation result. [S001] [S003] [S005] [S010]