What each Feetech servo can do, keyed on the model_number it reports.

These servos have no torque goal — torque_limit is a ceiling expressed as a fraction of the model's rated stall torque, so turning a Command.Effort in newton metres into a register value needs that rating, and the rating is not readable from the bus.

The numbers are approximate, and 777 is worse than that

Model number does not identify a servo. An STS3215 reports 777 whether it is a 7.4 V 1:345 (19.5 kgf·cm), a 7.4 V 1:191 (27.4 kgf·cm), or a 12 V 1:345 (30 kgf·cm) — a 1.5× spread. The figure below is the 1:345 7.4 V variant, the one on an SO-ARM100/101, because it is the most common and because under-estimating stall torque errs towards a lower ceiling. If you have one of the others, set :stall_torque on the actuator; nothing here can work it out for you.

Even for the right variant, stall torque is quoted at the recommended supply voltage and falls with it, and the servo's own overload protection winds torque_limit down under sustained load. Treat effort as a rough ceiling rather than a calibrated torque.

Coverage

Only the models below are known. An unrecognised servo still drives in position and velocity mode — neither needs anything from this table — but effort is refused unless :stall_torque says what the servo can do.

SCS0009 (1284) is deliberately absent: it is an SCSCL-family servo with a different control table, which the feetech library does not implement.