The EROS architecture used in the RH8D exposes multiple interfaces and protocol options, such as the Seed Robotics STP protocols and the Dynamixel Protocol.
This document assumes you are familiar with the Dynamixel Protocol.

The RH8D, like all Seed Robotics products, can be connected directly to any chain of Dynamixel devices. It is compatible with TTL and RS485 devices (depending on your choice of model) and supports the Dynamixel 1.0 and 2.0 protocol.
It will operate on the bus like any other Dynamixel device, exposing its IDs and Control Table.

The RH8D ships configured with the following defaults on the main bus port (the one on the back of the unit):

Communication Settings

By default, the unit ships configured for operation at 1Mbps (8 data bits, no parity, 1 stop bit like all Dynamixel devices).

The unit operates in Half Duplex even if you have a Full Duplex electric interface: this means the host and the unit don't communicate simultaneously.
This is a feature of the Dynamixel Protocol which uses a master-slave model: the unit will only speak when the master (the host) sends a command. Once the command is received it is processed and the data requested (if any) is returned.

It is possible to change the communication speed from 9600bps up to 3Mbps. We recommend operating at 1Mbps.

Default I Ds

The RH8D exposes 9 IDs on the bus:

  • 1 ID for the main control board where you can query the high-level functionality of the system as well as get all real-time current measurements at once and readings for all sensors (Capacitive, Palm Optical Sensors and Wrist Adduction and Wrist Flexion sensors if series elastic joints are installed).
  • 8 IDs for the actuators: each actuator has its own ID and individual Control table. The Control table is a memory map where you can query READ the status of the joint (position, speed, temperature, etc.) and WRITE comands (to set a new target position for example or adjust tuning parameters such as PID).

For ease of use, we pre configure each hand with all IDs in a sequence. Furthermore, each ID is connected to a main board port that is directly related to the ID number. To get the board port, take the last digit of the ID and subtract it by 1.

For example, for ID 34, take the last digit - 4 - and subtract 1, becoming 3. This ID is connected to the main board port 3, where you will be able to find the current reading that is externally measured for the joint.

The default IDs can be changed to suit the user needs. However, for ease of use, we recommend keeping some form of relation between the ID number and the port number on the board.

Default IDs for a Left Hand

  • 40 Main board
  • 41 Wrist Rotation
  • 42 Wrist Adduction
  • 43 Wrist Flexion
  • 44 Thumb Adduction
  • 45 Thumb Flexion
  • 46 Index Flexion
  • 47 Middle finger Flexion
  • 48 4th and 5th finger flexion (with tendon tension equalization to conform to the object shape).

Default IDs for a Right Hand

  • 30 Main board
  • 31 Wrist Rotation
  • 32 Wrist Adduction
  • 33 Wrist Flexion
  • 34 Thumb Adduction
  • 35 Thumb Flexion
  • 36 Index Flexion
  • 37 Middle finger Flexion
  • 38 4th and 5th finger flexion (with tendon tension equalization to conform to the object shape).

For further information on controlling the unit, please consult the RH8D Control Tables.

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  • rh8d/dynamixelidsandcommsettings.txt
  • Last modified: 2018/02/01 13:40
  • by pedro.ramilo