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Sample Code

MATLAB Protocol 1.0

Matlab Sync Write Protocol 1.0

Sample code Parts

%
% sync_write.c
%
%  Created on: 2016. 5. 24.
%      Author: Ryu Woon Jung (Leon)
%

%
% %%%%%%%%%     Sync Write Example      %%%%%%%%%
%
%
% Available Dynamixel model on this example : All models using Protocol 1.0
% This example is designed for using two Dynamixel MX-28, and an USB2DYNAMIXEL.
% To use another Dynamixel model, such as X series, see their details in E-Manual(support.robotis.com) and edit below variables yourself.
% Be sure that Dynamixel MX properties are already set as %% ID : 1 / Baudnum : 1 (Baudrate : 1000000 [1M])
%

clc;
clear all;

% Load Libraries
if ~libisloaded('dxl_x86_c');
    [notfound, warnings] = loadlibrary('dxl_x86_c', 'dynamixel_sdk.h', 'addheader', 'port_handler.h', 'addheader', 'packet_handler.h', 'addheader', 'group_sync_write.h');
end

% Control table address
ADDR_MX_TORQUE_ENABLE       = 24;           % Control table address is different in Dynamixel model
ADDR_MX_GOAL_POSITION       = 30;
ADDR_MX_PRESENT_POSITION    = 36;

% Data Byte Length
LEN_MX_GOAL_POSITION        = 2;
LEN_MX_PRESENT_POSITION     = 2;

% Protocol version
PROTOCOL_VERSION            = 1.0;          % See which protocol version is used in the Dynamixel

% Default setting
DXL1_ID                     = 1;            % Dynamixel#1 ID: 1
DXL2_ID                     = 2;            % Dynamixel#2 ID: 2
BAUDRATE                    = 1000000;
DEVICENAME                  = 'COM1';       % Check which port is being used on your controller
                                            % ex) Windows: "COM1"   Linux: "/dev/ttyUSB0"

TORQUE_ENABLE               = 1;            % Value for enabling the torque
TORQUE_DISABLE              = 0;            % Value for disabling the torque
DXL_MINIMUM_POSITION_VALUE  = 100;          % Dynamixel will rotate between this value
DXL_MAXIMUM_POSITION_VALUE  = 4000;         % and this value (note that the Dynamixel would not move when the position value is out of movable range. Check e-manual about the range of the Dynamixel you use.)
DXL_MOVING_STATUS_THRESHOLD = 10;           % Dynamixel moving status threshold

ESC_CHARACTER               = 'e';          % Key for escaping loop

COMM_SUCCESS                = 0;            % Communication Success result value
COMM_TX_FAIL                = -1001;        % Communication Tx Failed

% Initialize PortHandler Structs
% Set the port path
% Get methods and members of PortHandlerLinux or PortHandlerWindows
port_num = portHandler(DEVICENAME);

% Initialize PacketHandler Structs
packetHandler();

% Initialize Groupsyncwrite instance
group_num = groupSyncWrite(port_num, PROTOCOL_VERSION, ADDR_MX_GOAL_POSITION, LEN_MX_GOAL_POSITION);

index = 1;
dxl_comm_result = COMM_TX_FAIL;             % Communication result
dxl_addparam_result = false;                % AddParam result
dxl_goal_position = [DXL_MINIMUM_POSITION_VALUE DXL_MAXIMUM_POSITION_VALUE];         % Goal position

dxl_error = 0;                              % Dynamixel error
dxl1_present_position = 0;                  % Present position
dxl2_present_position = 0;


% Open port
if (openPort(port_num))
    fprintf('Succeeded to open the port!\n');
else
    unloadlibrary('dxl_x86_c');
    fprintf('Failed to open the port!\n');
    input('Press any key to terminate...\n');
    return;
end


% Set port baudrate
if (setBaudRate(port_num, BAUDRATE))
    fprintf('Succeeded to change the baudrate!\n');
else
    unloadlibrary('dxl_x86_c');
    fprintf('Failed to change the baudrate!\n');
    input('Press any key to terminate...\n');
    return;
end


% Enable Dynamixel#1 Torque
write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL1_ID, ADDR_MX_TORQUE_ENABLE, TORQUE_ENABLE);
if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
    printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
    printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
else
    fprintf('Dynamixel has been successfully connected \n');
end

% Enable Dynamixel#2 Torque
write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL2_ID, ADDR_MX_TORQUE_ENABLE, TORQUE_ENABLE);
if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
    printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
    printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
else
    fprintf('Dynamixel has been successfully connected \n');
end


while 1
    if input('Press any key to continue! (or input e to quit!)\n', 's') == ESC_CHARACTER
        break;
    end

    % Add Dynamixel#1 goal position value to the Syncwrite storage
    dxl_addparam_result = groupSyncWriteAddParam(group_num, DXL1_ID, dxl_goal_position(index), LEN_MX_GOAL_POSITION);
    if dxl_addparam_result ~= true
        fprintf('[ID:%03d] groupSyncWrite addparam failed', DXL1_ID);
        return;
    end

    % Add Dynamixel#2 goal position value to the Syncwrite parameter storage
    dxl_addparam_result = groupSyncWriteAddParam(group_num, DXL2_ID, dxl_goal_position(index), LEN_MX_GOAL_POSITION);
    if dxl_addparam_result ~= true
        fprintf('[ID:%03d] groupSyncWrite addparam failed', DXL2_ID);
        return;
    end

    % Syncwrite goal position
    groupSyncWriteTxPacket(group_num);
    if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
        printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
    end

    % Clear syncwrite parameter storage
    groupSyncWriteClearParam(group_num);

    while 1
        % Read Dynamixel#1 present position
        dxl1_present_position = read2ByteTxRx(port_num, PROTOCOL_VERSION, DXL1_ID, ADDR_MX_PRESENT_POSITION);
        if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
            printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
        elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
            printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
        end

        % Read Dynamixel#2 present position
        dxl2_present_position = read2ByteTxRx(port_num, PROTOCOL_VERSION, DXL2_ID, ADDR_MX_PRESENT_POSITION);
        if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
            printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
        elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
            printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
        end

        fprintf('[ID:%03d] GoalPos:%03d  PresPos:%03d\t[ID:%03d] GoalPos:%03d  PresPos:%03d\n', DXL1_ID, dxl_goal_position(index), dxl1_present_position, DXL2_ID, dxl_goal_position(index), dxl2_present_position);

        if ~((abs(dxl_goal_position(index) - dxl1_present_position) > DXL_MOVING_STATUS_THRESHOLD) || (abs(dxl_goal_position(index) - dxl2_present_position) > DXL_MOVING_STATUS_THRESHOLD))
            break;
        end
    end

    % Change goal position
    if index == 1
        index = 2;
    else
        index = 1;
    end
end


% Disable Dynamixel#1 Torque
write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL1_ID, ADDR_MX_TORQUE_ENABLE, TORQUE_DISABLE);
if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
    printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
    printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
end

% Disable Dynamixel#2 Torque
write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL2_ID, ADDR_MX_TORQUE_ENABLE, TORQUE_DISABLE);
if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
    printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
    printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
end

% Close port
closePort(port_num);

% Unload Library
unloadlibrary('dxl_x86_c');

close all;
clear all;

Details

% Load Libraries
if ~libisloaded('dxl_x86_c');
    [notfound, warnings] = loadlibrary('dxl_x86_c', 'dynamixel_sdk.h', 'addheader', 'port_handler.h', 'addheader', 'packet_handler.h', 'addheader', 'group_sync_write.h');
end

This example uses dynamixel library imported by loadlibrary().

% Control table address
ADDR_MX_TORQUE_ENABLE       = 24;           % Control table address is different in Dynamixel model
ADDR_MX_GOAL_POSITION       = 30;
ADDR_MX_PRESENT_POSITION    = 36;

% Data Byte Length
LEN_MX_GOAL_POSITION        = 2;
LEN_MX_PRESENT_POSITION     = 2;

Dynamixel series have their own control tables: Addresses and Byte Length in each items. To control one of the items, its address (and length if necessary) is required. Find your requirements in http://support.robotis.com/.

% Protocol version
PROTOCOL_VERSION            = 1.0;          % See which protocol version is used in the Dynamixel

Dynamixel uses either or both protocols: Protocol 1.0 and Protocol 2.0. Choose one of the Protocol which is appropriate in the Dynamixel.

% Default setting
DXL1_ID                     = 1;            % Dynamixel#1 ID: 1
DXL2_ID                     = 2;            % Dynamixel#2 ID: 2
BAUDRATE                    = 1000000;
DEVICENAME                  = 'COM1';       % Check which port is being used on your controller
                                            % ex) Windows: "COM1"   Linux: "/dev/ttyUSB0"

TORQUE_ENABLE               = 1;            % Value for enabling the torque
TORQUE_DISABLE              = 0;            % Value for disabling the torque
DXL_MINIMUM_POSITION_VALUE  = 100;          % Dynamixel will rotate between this value
DXL_MAXIMUM_POSITION_VALUE  = 4000;         % and this value (note that the Dynamixel would not move when the position value is out of movable range. Check e-manual about the range of the Dynamixel you use.)
DXL_MOVING_STATUS_THRESHOLD = 10;           % Dynamixel moving status threshold

ESC_CHARACTER               = 'e';          % Key for escaping loop

Here we set some variables to let you freely change them and use them to run the example code.

As the document previously said in previous chapter, customize Dynamixel control table items, such as DXL_ID number, communication BAUDRATE, and the DEVICENAME, on your own terms of needs. In particular, BAUDRATE and DEVICENAME have systematical dependencies on your controller, so make clear what kind of communication method you will use.

The example uses two Dynamixels DXL1_ID, DXL2_ID connected with the port DEVICENAME.

Dynamixel basically needs the TORQUE_ENABLE to be rotating or give you its internal information. On the other hand, it doesn’t need torque enabled if you get your goal, so finally do TORQUE_DISABLE to prepare to the next sequence.

Since the Dynamixel has its own rotation range, it may shows malfunction if your request on your dynamixel is out of range. For example, Dynamixel MX-28 and Dynamixel PRO 54-200 has its rotatable range as 0 ~ 4028 and -250950 ~ 250950, each.

DXL_MOVING_STATUS_THRESHOLD acts as a criteria for verifying its rotation stopped.

COMM_SUCCESS                = 0;            % Communication Success result value
COMM_TX_FAIL                = -1001;        % Communication Tx Failed

Each of the variables above show the meaning of the communication result value.

% Initialize PortHandler Structs
% Set the port path
% Get methods and members of PortHandlerLinux or PortHandlerWindows
port_num = portHandler(DEVICENAME);

portHandler() function sets port path as DEVICENAME and get port_num, and prepares an appropriate functions for port control in controller OS automatically. port_num would be used in many functions in the body of the code to specify the port for use.

% Initialize PacketHandler Structs
packetHandler();

packetHandler() function initializes parameters used for packet construction and packet storing.

% Initialize Groupsyncwrite instance
group_num = groupSyncWrite(port_num, PROTOCOL_VERSION, ADDR_MX_GOAL_POSITION, LEN_MX_GOAL_POSITION);

groupSyncWrite() function initializes grouped parameters used for packet construction and packet storing. The utility functions of sync write deals simultaneously with more than one Dynamixel through #port_num port, building packets by the function which uses PROTOCOL_VERSION, and writing LEN_MX_GOAL_POSITION bytes of the values on the address ADDR_MX_GOAL_POSITION.

index = 1;
dxl_comm_result = COMM_TX_FAIL;             % Communication result
dxl_addparam_result = false;                % AddParam result
dxl_goal_position = [DXL_MINIMUM_POSITION_VALUE DXL_MAXIMUM_POSITION_VALUE];         % Goal position

dxl_error = 0;                              % Dynamixel error
dxl1_present_position = 0;                  % Present position
dxl2_present_position = 0;

index variable points the direction to where the Dynamixel should be rotated.

dxl_comm_result indicates which error has been occurred during packet communication.

dxl_addparam_result indicates the result of parameter addition used for sync/bulk related functions

dxl_goal_position stores goal points of Dynamixel rotation.

dxl_error shows the internal error in Dynamixel.

dxl1_present_position and dxl2_present_position view where now each Dynamixel points out.

% Open port
if (openPort(port_num))
    fprintf('Succeeded to open the port!\n');
else
    unloadlibrary('dxl_x86_c');
    fprintf('Failed to open the port!\n');
    input('Press any key to terminate...\n');
    return;
end

First, controller opens #port_num port to do serial communication with the Dynamixel. If it fails to open the port, the example will be terminated.

% Set port baudrate
if (setBaudRate(port_num, BAUDRATE))
    fprintf('Succeeded to change the baudrate!\n');
else
    unloadlibrary('dxl_x86_c');
    fprintf('Failed to change the baudrate!\n');
    input('Press any key to terminate...\n');
    return;
end

Secondly, the controller sets the communication BAUDRATE at #port_num port opened previously.

% Enable Dynamixel#1 Torque
write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL1_ID, ADDR_MX_TORQUE_ENABLE, TORQUE_ENABLE);
if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
    printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
    printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
else
    fprintf('Dynamixel has been successfully connected \n');
end

% Enable Dynamixel#2 Torque
write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL2_ID, ADDR_MX_TORQUE_ENABLE, TORQUE_ENABLE);
if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
    printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
    printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
else
    fprintf('Dynamixel has been successfully connected \n');
end

As mentioned in the document, above code enables each Dynamixel`s torque to set their status as being ready to move.

write1ByteTxRx() function orders to the #DXL1_ID and #DXL2_ID Dynamixels in PROTOCOL_VERSION communication protocol through #port_num port, writing 1 byte of TORQUE_ENABLE value to ADDR_MX_TORQUE_ENABLE address. The function checks Tx/Rx result and receives Hardware error. getLastTxRxResult() function and getLastRxPacketError() function get either, and then printTxRxResult() function and printRxPacketError() function show results on the console window if any communication error or Hardware error has been occurred.

while 1
    if input('Press any key to continue! (or input e to quit!)\n', 's') == ESC_CHARACTER
        break;
    end

    % Add Dynamixel#1 goal position value to the Syncwrite storage
    dxl_addparam_result = groupSyncWriteAddParam(group_num, DXL1_ID, dxl_goal_position(index), LEN_MX_GOAL_POSITION);
    if dxl_addparam_result ~= true
        fprintf('[ID:%03d] groupSyncWrite addparam failed', DXL1_ID);
        return;
    end

    % Add Dynamixel#2 goal position value to the Syncwrite parameter storage
    dxl_addparam_result = groupSyncWriteAddParam(group_num, DXL2_ID, dxl_goal_position(index), LEN_MX_GOAL_POSITION);
    if dxl_addparam_result ~= true
        fprintf('[ID:%03d] groupSyncWrite addparam failed', DXL2_ID);
        return;
    end

    % Syncwrite goal position
    groupSyncWriteTxPacket(group_num);
    if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
        printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
    end

    % Clear syncwrite parameter storage
    groupSyncWriteClearParam(group_num);

    while 1
        % Read Dynamixel#1 present position
        dxl1_present_position = read2ByteTxRx(port_num, PROTOCOL_VERSION, DXL1_ID, ADDR_MX_PRESENT_POSITION);
        if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
            printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
        elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
            printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
        end

        % Read Dynamixel#2 present position
        dxl2_present_position = read2ByteTxRx(port_num, PROTOCOL_VERSION, DXL2_ID, ADDR_MX_PRESENT_POSITION);
        if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
            printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
        elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
            printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
        end

        fprintf('[ID:%03d] GoalPos:%03d  PresPos:%03d\t[ID:%03d] GoalPos:%03d  PresPos:%03d\n', DXL1_ID, dxl_goal_position(index), dxl1_present_position, DXL2_ID, dxl_goal_position(index), dxl2_present_position);

        if ~((abs(dxl_goal_position(index) - dxl1_present_position) > DXL_MOVING_STATUS_THRESHOLD) || (abs(dxl_goal_position(index) - dxl2_present_position) > DXL_MOVING_STATUS_THRESHOLD))
            break;
        end
    end

    % Change goal position
    if index == 1
        index = 2;
    else
        index = 1;
    end
end

During while loop, the controller writes and reads each Dynamixel position through packet transmission/reception(Tx/Rx).

To continue their rotation, press any key except ESC.

groupSyncWriteAddParam() function stores the Dynamixel ID and its LEN_MX_GOAL_POSITION bytes goal position dxl_goal_position to the syncwrite target Dynamixel list.

groupSyncWriteTxPacket() function orders to the Dynamixel #DXL1_ID and #DXL2_ID at the same time through #port_num, making it possible to write same pre-listed length bytes to same pre-listed address. The function checks Tx/Rx result. getLastTxRxResult() function gets it, and then printTxRxResult() function shows result on the console window if any communication error has been occurred.

groupSyncWriteClearParam() function clears the Dynamixel list of groupsyncwrite.

read2ByteTxRx() function orders to the #DXL1_ID and #DXL2_ID Dynamixels in PROTOCOL_VERSION communication protocol through #port_num port, requesting 2 bytes of value in ADDR_MX_PRESENT_POSITION address. The function checks Tx/Rx result and receives Hardware error. getLastTxRxResult() function and getLastRxPacketError() function get either, and then printTxRxResult() function and printRxPacketError() function show results on the console window if any communication error or Hardware error has been occurred.

Reading their present position will be ended when absolute value of (dxl_goal_position[index] - dxl1_present_position) or (dxl_goal_position[index] - dxl2_present_position) becomes smaller then DXL_MOVING_STATUS_THRESHOLD.

At last, it changes their direction to the counter-wise and waits for extra key input.

% Disable Dynamixel#1 Torque
write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL1_ID, ADDR_MX_TORQUE_ENABLE, TORQUE_DISABLE);
if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
    printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
    printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
end

% Disable Dynamixel#2 Torque
write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL2_ID, ADDR_MX_TORQUE_ENABLE, TORQUE_DISABLE);
if getLastTxRxResult(port_num, PROTOCOL_VERSION) ~= COMM_SUCCESS
    printTxRxResult(PROTOCOL_VERSION, getLastTxRxResult(port_num, PROTOCOL_VERSION));
elseif getLastRxPacketError(port_num, PROTOCOL_VERSION) ~= 0
    printRxPacketError(PROTOCOL_VERSION, getLastRxPacketError(port_num, PROTOCOL_VERSION));
end

The controller frees the Dynamixels to be idle.

write1ByteTxRx() function orders to the #DXL1_ID and #DXL2_ID Dynamixels in PROTOCOL_VERSION communication protocol through #port_num port, writing 1 byte of TORQUE_DISABLE value to ADDR_MX_TORQUE_ENABLE address. The function checks Tx/Rx result and receives Hardware error. getLastTxRxResult() function and getLastRxPacketError() function get either, and then printTxRxResult() function and printRxPacketError() function show results on the console window if any communication error or Hardware error has been occurred.

% Close port
closePort(port_num);

Finally, port becomes disposed.

% Unload Library
unloadlibrary('dxl_x86_c');

Unload the library to make it reaccessible.