Model support

Which servos the driver knows by model number, what "knows" gives you, and how to run a servo it does not list.

The catalog

Device::Identify() pings the servo and looks its model number up in kKnownModels (inc/dynamixel_model.hpp). Every entry is built by MakeXSeries() and shares the X-series control table (Hardware); they differ only in two flags.

Constant	Model number	Address 126 is
kXc430W150	1070	Present Load
kXc430W240	1080	Present Load
kXl430W250	1060	Present Load
kXm430W210	1030	Present Current
kXm430W350	1020	Present Current
kXh430W210	1010	Present Current
kXh430W350	1000	Present Current
kXSeriesFallback	0 (any)	treated as Present Load

The XC430-W150 is the servo the driver was validated on. The XM and XH entries set supports_current and effort_is_current; read servo.model()->effort_is_current before treating Telemetry::load as current.

What a bound model gives you

Without a model, Device's typed calls return UnsupportedRequest; ReadRegister() and WriteRegister() still work. With one:

Call	Needs
SetTorqueEnabled(), SetMotionProfile(), ReadPosition(), ReadTelemetry()	A model
SetOperatingMode()	A model, and torque off (else Busy)
SetGoalPosition()	Mode Position or Extended Position
SetGoalVelocity()	Mode Velocity
SetGoalPwm()	Mode PWM (16), and a model with supports_pwm

Identify() also reads the servo's Operating Mode and caches it; SetOperatingMode() updates the cache, and operating_mode() returns it. A register value without a typed mode (current 0, current-based position 5, or a value the control table does not define) is cached as OperatingMode::Unknown, with the raw byte in operating_mode_raw(). A goal for another mode, or any goal while the mode is Unknown, is refused before anything is sent.

A servo the catalog does not list

1. Identify() returns UnsupportedRequest with ping.value.model_number filled in: the servo answered.
2. Call BindXSeriesFallback() to use the shared X-series addresses, or bind a descriptor of your own with BindModel() before calling Identify() again. A bound descriptor survives Identify() when its model_number is 0 or matches the ping.
3. When the part is settled, add a MakeXSeries() entry to kKnownModels, with supports_current and effort_is_current from the model's e-Manual page, so Identify() binds it by itself.

Configuration shows a descriptor for the XM540-W270 (model 1120).

Out of scope

• Protocol 1.0, the MX, AX and DYNAMIXEL-P series: their control tables differ.
• Typed current control: write Goal Current (address 102) with WriteRegister() and set Operating Mode 0 or 5 yourself. OperatingMode lists only velocity (1), position (3), extended position (4) and PWM (16).
• Bulk Read and Bulk Write instructions.