Robotis

Driver for interfacing with Robotis Dynamixel servos.

This is a work in progress and currently supports XL320, XL330, and XM430 series servos. It only speaks Dynamixel protocol v2.

While it is possible to support GPIO-based switching for converting UART to the half-duplex signal required by Dynamixel, this library works best speaking UART over USB to another device that can do that conversion (such as and OpenR150 running the usb_to_dynamixel sketch.

Installation

def deps do
  [
    {:robotis, "~> 0.2.0"}
  ]
end

Usage

{:ok, pid} = Robotis.start_link(uart_port: "ttyAMA0", baud: 1_000_000, control_table: Robotis.ControlTable.XL330)

Robotis.ping(pid, 1) # => {:ok, %{firmware: 49, id: 1, model: :xl330_m288, model_number: 1200}}
Robotis.read(pid, 1, :present_position) # => {:ok, 14.58984375}
:ok = Robotis.write(pid, 1, :torque_enable, true)
:ok = Robotis.write(pid, 1, :goal_position, 124.293)

Control Tables

This library uses control tables to define the registers available on different Dynamixel models. Currently, the library contains the following control tables:

• Robotis.ControlTable.XL320
• Robotis.ControlTable.XL330
• Robotis.ControlTable.XM430

You can also define your own control tables by creating a module that implements the Robotis.ControlTable behaviour and defines the necessary registers.

## Write or Write-and-Wait

The `Robotis.write/5` function can work in either a write or write-and-wait manner:

```elixir
# The default, this will send the command to the servo and not wait for a
# response.
:ok = Robotis.write(pid, 1, :goal_position, 180)

# This will send the command and wait for a status packet from the servo. This
# will block until that status packet is received or a timeout occurs
:ok = Robotis.write(pid, 1, :goal_position, 180, true)

It's important to consider the setting of :status_return_level when deciding which to use. In the case that :status_return_level is set to :all, the servo will respond with a status message after the write. If the Robotis.write call is not expecting this and another command is issued, it's possible the status message and the new command will conflict and have unintended consequences.

# The following may receive no data or invalid packets when reading present_position
:ok = Robotis.write(pid, 1, :status_return_level, :all)
:ok = Robotis.write(pid, 1, :goal_position, 180)
:ok = Robotis.read(pid, 1, :present_position)

# The following will work
:ok = Robotis.write(pid, 1, :status_return_level, :ping_read)
:ok = Robotis.write(pid, 1, :goal_position, 180)
:ok = Robotis.read(pid, 1, :present_position)