DYNAMIXEL SDK

Python Indirect Address Protocol 2.0

Description

This example writes the goal position and LED value and repeats to read present position and moving status through the indirect data storage, rather than write directly to the their own data storages. The indirect address links between direct and indirect data storages. This makes the Syncread and the Syncwrite function accessible to the items which are far from each other’s address.
Available Dynamixel

All series using protocol 2.0

Sample code

#!/usr/bin/env python
# -*- coding: utf-8 -*-

#
# indirect_address.py
#
#  Created on: 2016. 6. 16.
#      Author: Ryu Woon Jung (Leon)
#

#
# *********     Indirect Address Example      *********
#
#
# Available Dynamixel model on this example : All models using Protocol 2.0
# This example is designed for using a Dynamixel PRO 54-200, 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 PRO properties are already set as %% ID : 1 / Baudnum : 3 (Baudrate : 1000000 [1M])
#

import os, sys, ctypes

if os.name == 'nt':
    import msvcrt
    def getch():
        return msvcrt.getch().decode()
else:
    import tty, termios
    fd = sys.stdin.fileno()
    old_settings = termios.tcgetattr(fd)
    tty.setraw(sys.stdin.fileno())
    def getch():
        return sys.stdin.read(1)

os.sys.path.append('../dynamixel_functions_py')             # Path setting

import dynamixel_functions as dynamixel                     # Uses DYNAMIXEL SDK library

# Control table address                                     # Control table address is different in Dynamixel model
ADDR_PRO_INDIRECTADDRESS_FOR_WRITE      = 49                # EEPROM region
ADDR_PRO_INDIRECTADDRESS_FOR_READ       = 59                # EEPROM region
ADDR_PRO_TORQUE_ENABLE                  = 562
ADDR_PRO_LED_RED                        = 563
ADDR_PRO_GOAL_POSITION                  = 596
ADDR_PRO_MOVING                         = 610
ADDR_PRO_PRESENT_POSITION               = 611
ADDR_PRO_INDIRECTDATA_FOR_WRITE         = 634
ADDR_PRO_INDIRECTDATA_FOR_READ          = 639

# Data Byte Length
LEN_PRO_LED_RED                         = 1
LEN_PRO_GOAL_POSITION                   = 4
LEN_PRO_MOVING                          = 1
LEN_PRO_PRESENT_POSITION                = 4
LEN_PRO_INDIRECTDATA_FOR_WRITE          = 5
LEN_PRO_INDIRECTDATA_FOR_READ           = 5

# Protocol version
PROTOCOL_VERSION            = 2                             # See which protocol version is used in the Dynamixel

# Default setting
DXL_ID                      = 1                             # Dynamixel ID: 1
BAUDRATE                    = 1000000
DEVICENAME                  = "/dev/ttyUSB0".encode('utf-8')        # 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  = -150000                       # Dynamixel will rotate between this value
DXL_MAXIMUM_POSITION_VALUE  = 150000                        # 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 = 20                            # Dynamixel moving status threshold

ESC_ASCII_VALUE             = 0x1b

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 = dynamixel.portHandler(DEVICENAME)

# Initialize PacketHandler Structs
dynamixel.packetHandler()

# Initialize Groupsyncwrite instance
groupwrite_num = dynamixel.groupSyncWrite(port_num, PROTOCOL_VERSION, ADDR_PRO_INDIRECTDATA_FOR_WRITE, LEN_PRO_INDIRECTDATA_FOR_WRITE)

# Initialize Groupsyncread Structs for Present Position
groupread_num = dynamixel.groupSyncRead(port_num, PROTOCOL_VERSION, ADDR_PRO_INDIRECTDATA_FOR_READ, LEN_PRO_INDIRECTDATA_FOR_READ)

index = 0
dxl_comm_result = COMM_TX_FAIL                              # Communication result
dxl_addparam_result = 0                                     # AddParam result
dxl_getdata_result = 0                                      # GetParam result
dxl_goal_position = [DXL_MINIMUM_POSITION_VALUE, DXL_MAXIMUM_POSITION_VALUE]         # Goal position

dxl_error = 0                                               # Dynamixel error
dxl_moving = 0                                              # Dynamixel moving status
dxl_led_value = [0x00, 0xFF]                                # Dynamixel LED value
dxl_present_position = 0                                    # Present position

# Open port
if dynamixel.openPort(port_num):
    print("Succeeded to open the port!")
else:
    print("Failed to open the port!")
    print("Press any key to terminate...")
    getch()
    quit()

# Set port baudrate
if dynamixel.setBaudRate(port_num, BAUDRATE):
    print("Succeeded to change the baudrate!")
else:
    print("Failed to change the baudrate!")
    print("Press any key to terminate...")
    getch()
    quit()


# Disable Dynamixel Torque :
# Indirect address would not accessible when the torque is already enabled
dynamixel.write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_TORQUE_ENABLE, TORQUE_DISABLE)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))
else:
    print("Dynamixel has been successfully connected")

# INDIRECTDATA parameter storages replace LED, goal position, present position and moving status storages
dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 0, ADDR_PRO_GOAL_POSITION + 0)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 2, ADDR_PRO_GOAL_POSITION + 1)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 4, ADDR_PRO_GOAL_POSITION + 2)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 6, ADDR_PRO_GOAL_POSITION + 3)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 8, ADDR_PRO_LED_RED)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 0, ADDR_PRO_PRESENT_POSITION + 0)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 2, ADDR_PRO_PRESENT_POSITION + 1)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 4, ADDR_PRO_PRESENT_POSITION + 2)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 6, ADDR_PRO_PRESENT_POSITION + 3)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 8, ADDR_PRO_MOVING)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

# Enable Dynamixel Torque
dynamixel.write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_TORQUE_ENABLE, TORQUE_ENABLE)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

# Add parameter storage for Dynamixel present position value
dxl_addparam_result = ctypes.c_ubyte(dynamixel.groupSyncReadAddParam(groupread_num, DXL_ID)).value
if dxl_addparam_result != 1:
    print("[ID:%03d] groupSyncRead addparam failed" % (DXL_ID))
    quit()


while 1:
    print("Press any key to continue! (or press ESC to quit!)")
    if getch() == chr(ESC_ASCII_VALUE):
        break

    # Add Dynamixel#1 goal position value to the Syncwrite storage
    dxl_addparam_result = ctypes.c_ubyte(dynamixel.groupSyncWriteAddParam(groupwrite_num, DXL_ID, dxl_goal_position[index], LEN_PRO_GOAL_POSITION)).value
    print(dxl_addparam_result)
    if dxl_addparam_result != 1:
        print("[ID:%03d] groupSyncWrite addparam failed" % (DXL_ID))
        quit()

    # Add Dynamixel#2 goal position value to the Syncwrite parameter storage
    dxl_addparam_result = ctypes.c_ubyte(dynamixel.groupSyncWriteAddParam(groupwrite_num, DXL_ID, dxl_led_value[index], LEN_PRO_LED_RED)).value
    if dxl_addparam_result != 1:
        print("[ID:%03d] groupSyncWrite addparam failed" % (DXL_ID))
        quit()

    # Syncwrite goal position
    dynamixel.groupSyncWriteTxPacket(groupwrite_num)
    if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
        dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))

    # Clear syncwrite parameter storage
    dynamixel.groupSyncWriteClearParam(groupwrite_num)

    while 1:
        # Syncread present position
        dynamixel.groupSyncReadTxRxPacket(groupread_num)
        if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
            dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))

        # Check if groupsyncread data of Dynamixel#1 is available
        dxl_getdata_result = ctypes.c_ubyte(dynamixel.groupSyncReadIsAvailable(groupread_num, DXL_ID, ADDR_PRO_INDIRECTDATA_FOR_READ, LEN_PRO_PRESENT_POSITION)).value
        if dxl_getdata_result != 1:
            print("[ID:%03d] groupSyncRead getdata failed" % (DXL_ID))
            quit()

        # Check if groupsyncread data of Dynamixel#2 is available
        dxl_getdata_result = ctypes.c_ubyte(dynamixel.groupSyncReadIsAvailable(groupread_num, DXL_ID, ADDR_PRO_INDIRECTDATA_FOR_READ + LEN_PRO_PRESENT_POSITION, LEN_PRO_MOVING)).value
        if dxl_getdata_result != 1:
            print("[ID:%03d] groupSyncRead getdata failed" % (DXL_ID))
            quit()

        # Get Dynamixel#1 present position value
        dxl_present_position = dynamixel.groupSyncReadGetData(groupread_num, DXL_ID, ADDR_PRO_INDIRECTDATA_FOR_READ, LEN_PRO_PRESENT_POSITION)

        # Get Dynamixel#2 present position value
        dxl_moving = dynamixel.groupSyncReadGetData(groupread_num, DXL_ID, ADDR_PRO_INDIRECTDATA_FOR_READ + LEN_PRO_PRESENT_POSITION, LEN_PRO_MOVING)

        print("[ID:%03d] GoalPos:%d  PresPos:%d  IsMoving:%d" % (DXL_ID, dxl_goal_position[index], dxl_present_position, dxl_moving))

        if not (abs(dxl_goal_position[index] - dxl_present_position) > DXL_MOVING_STATUS_THRESHOLD):
            break

    # Change goal position
    if index == 0:
        index = 1
    else:
        index = 0


# Disable Dynamixel Torque
dynamixel.write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_TORQUE_ENABLE, TORQUE_DISABLE)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))


# Close port
dynamixel.closePort(port_num)

Details

import os, sys, ctypes

if os.name == 'nt':
    import msvcrt
    def getch():
        return msvcrt.getch().decode()
else:
    import tty, termios
    fd = sys.stdin.fileno()
    old_settings = termios.tcgetattr(fd)
    tty.setraw(sys.stdin.fileno())
    def getch():
        return sys.stdin.read(1)

os.sys.path.append('../dynamixel_functions_py')             # Path setting

import dynamixel_functions as dynamixel                     # Uses DYNAMIXEL SDK library

getch() gets the input which is for example code control.

os.sys.path.append() sets paths of function reference.

This example uses dynamixel_functions library as dynamixel imported from dynamixel_functions_py package.

# Control table address                                     # Control table address is different in Dynamixel model
ADDR_PRO_INDIRECTADDRESS_FOR_WRITE      = 49                # EEPROM region
ADDR_PRO_INDIRECTADDRESS_FOR_READ       = 59                # EEPROM region
ADDR_PRO_TORQUE_ENABLE                  = 562
ADDR_PRO_LED_RED                        = 563
ADDR_PRO_GOAL_POSITION                  = 596
ADDR_PRO_MOVING                         = 610
ADDR_PRO_PRESENT_POSITION               = 611
ADDR_PRO_INDIRECTDATA_FOR_WRITE         = 634
ADDR_PRO_INDIRECTDATA_FOR_READ          = 639

# Data Byte Length
LEN_PRO_LED_RED                         = 1
LEN_PRO_GOAL_POSITION                   = 4
LEN_PRO_MOVING                          = 1
LEN_PRO_PRESENT_POSITION                = 4
LEN_PRO_INDIRECTDATA_FOR_WRITE          = 5
LEN_PRO_INDIRECTDATA_FOR_READ           = 5

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://emanual.robotis.com/.

# Protocol version
PROTOCOL_VERSION            = 2                             # 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
DXL_ID                      = 1                             # Dynamixel ID: 1
BAUDRATE                    = 1000000
DEVICENAME                  = "/dev/ttyUSB0".encode('utf-8')        # 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  = -150000                       # Dynamixel will rotate between this value
DXL_MAXIMUM_POSITION_VALUE  = 150000                        # 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 = 20                            # Dynamixel moving status threshold

ESC_ASCII_VALUE             = 0x1b

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 Dynamixel DXL_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.

Dynamixel LED has its own range of value: 1 byte red LED for Dynamixel MX-28 and 1byte each on red, green, blue LED for Dynamixel PRO 54-200.

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 = dynamixel.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
dynamixel.packetHandler()

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

# Initialize Groupsyncwrite instance
groupwrite_num = dynamixel.groupSyncWrite(port_num, PROTOCOL_VERSION, ADDR_PRO_INDIRECTDATA_FOR_WRITE, LEN_PRO_INDIRECTDATA_FOR_WRITE)

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_PRO_INDIRECTDATA_FOR_WRITE bytes of the values on the address ADDR_PRO_INDIRECTDATA_FOR_WRITE.

# Initialize Groupsyncread Structs for Present Position
groupread_num = dynamixel.groupSyncRead(port_num, PROTOCOL_VERSION, ADDR_PRO_INDIRECTDATA_FOR_READ, LEN_PRO_INDIRECTDATA_FOR_READ)

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

index = 0
dxl_comm_result = COMM_TX_FAIL                              # Communication result
dxl_addparam_result = 0                                     # AddParam result
dxl_getdata_result = 0                                      # GetParam result
dxl_goal_position = [DXL_MINIMUM_POSITION_VALUE, DXL_MAXIMUM_POSITION_VALUE]         # Goal position

dxl_error = 0                                               # Dynamixel error
dxl_moving = 0                                              # Dynamixel moving status
dxl_led_value = [0x00, 0xFF]                                # Dynamixel LED value
dxl_present_position = 0                                    # Present position

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_getdata_result indicates the result of data reception used for sync/bulk related functions

dxl_goal_position stores goal points of Dynamixel rotation.

dxl_error shows the internal error in Dynamixel.

dxl_moving views whether the Dynamixel is stopped.

dxl_led_value stores LED values of Dynamixel.

dxl_present_position view where now each Dynamixel points out.

# Open port
if dynamixel.openPort(port_num):
    print("Succeeded to open the port!")
else:
    print("Failed to open the port!")
    print("Press any key to terminate...")
    getch()
    quit()

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 dynamixel.setBaudRate(port_num, BAUDRATE):
    print("Succeeded to change the baudrate!")
else:
    print("Failed to change the baudrate!")
    print("Press any key to terminate...")
    getch()
    quit()

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

# Disable Dynamixel Torque :
# Indirect address would not accessible when the torque is already enabled
dynamixel.write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_TORQUE_ENABLE, TORQUE_DISABLE)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))
else:
    print("Dynamixel has been successfully connected")

Indirect address and Indirect data are particularly applicable to control several items far from each other in control table address simultaenously. Nth Indirect data shows one of the item on the control table that Nth Indirect Address points out, so if you want to see Dynamixel LED RED value through 1st indirect data, change value of 1st Indirect Address to ADDR_PRO_LED_RED value.

However, Dynamixel PRO has Indirect Address items on its EEPROM area. (Please see the E-Manual.) To change them, you must disable the torque at first.

Above write1ByteTxRx() function sends an instruction to the #DXL_ID Dynamixel through the port, writing 1 byte of TORQUE_DISABLE value to ADDR_PRO_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.

# INDIRECTDATA parameter storages replace LED, goal position, present position and moving status storages
dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 0, ADDR_PRO_GOAL_POSITION + 0)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 2, ADDR_PRO_GOAL_POSITION + 1)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 4, ADDR_PRO_GOAL_POSITION + 2)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 6, ADDR_PRO_GOAL_POSITION + 3)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 8, ADDR_PRO_LED_RED)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

These allocate five target address for writing (ADDR_PRO_GOAL_POSITION + 0, ADDR_PRO_GOAL_POSITION + 1, ADDR_PRO_GOAL_POSITION + 2, ADDR_PRO_GOAL_POSITION + 3 and ADDR_PRO_LED_RED) to the Indirect Addresses(ADDR_PRO_INDIRECTADDRESS_FOR_WRITE + 0 ~ 9) 2 bytes each. Now, you can change goal position value or red LED value by writing 4 byte and 1 byte each on the 1st ~ 4th and 5th Indirect Data item.

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 0, ADDR_PRO_PRESENT_POSITION + 0)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 2, ADDR_PRO_PRESENT_POSITION + 1)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 4, ADDR_PRO_PRESENT_POSITION + 2)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 6, ADDR_PRO_PRESENT_POSITION + 3)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

dynamixel.write2ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_INDIRECTADDRESS_FOR_READ + 8, ADDR_PRO_MOVING)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

These allocate five target address for writing (ADDR_PRO_PRESENT_POSITION + 0, ADDR_PRO_PRESENT_POSITION + 1, ADDR_PRO_PRESENT_POSITION + 2, ADDR_PRO_PRESENT_POSITION + 3 and ADDR_PRO_MOVING) to the Indirect Addresses(ADDR_PRO_INDIRECTADDRESS_FOR_READ + 0 ~ 9) 2 bytes each. Now, you can get present position value or moving status value by reading 4 byte and 1 byte each on the 6st ~ 9th and 10th Indirect Data item.

# Enable Dynamixel Torque
dynamixel.write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_TORQUE_ENABLE, TORQUE_ENABLE)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

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

write1ByteTxRx() function sends an instruction to the #DXL_ID Dynamixel in PROTOCOL_VERSION communication protocol through #port_num port, writing 1 byte of TORQUE_ENABLE value to ADDR_PRO_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.

# Add parameter storage for Dynamixel present position value
dxl_addparam_result = ctypes.c_ubyte(dynamixel.groupSyncReadAddParam(groupread_num, DXL_ID)).value
if dxl_addparam_result != 1:
    print("[ID:%03d] groupSyncRead addparam failed" % (DXL_ID))
    quit()

groupSyncReadAddParam() function stores the Dynamixel ID of required data to the syncread target Dynamixel list.

while 1:
    print("Press any key to continue! (or press ESC to quit!)")
    if getch() == chr(ESC_ASCII_VALUE):
        break

    # Add Dynamixel#1 goal position value to the Syncwrite storage
    dxl_addparam_result = ctypes.c_ubyte(dynamixel.groupSyncWriteAddParam(groupwrite_num, DXL_ID, dxl_goal_position[index], LEN_PRO_GOAL_POSITION)).value
    print(dxl_addparam_result)
    if dxl_addparam_result != 1:
        print("[ID:%03d] groupSyncWrite addparam failed" % (DXL_ID))
        quit()

    # Add Dynamixel#2 goal position value to the Syncwrite parameter storage
    dxl_addparam_result = ctypes.c_ubyte(dynamixel.groupSyncWriteAddParam(groupwrite_num, DXL_ID, dxl_led_value[index], LEN_PRO_LED_RED)).value
    if dxl_addparam_result != 1:
        print("[ID:%03d] groupSyncWrite addparam failed" % (DXL_ID))
        quit()

    # Syncwrite goal position
    dynamixel.groupSyncWriteTxPacket(groupwrite_num)
    if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
        dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))

    # Clear syncwrite parameter storage
    dynamixel.groupSyncWriteClearParam(groupwrite_num)

    while 1:
        # Syncread present position
        dynamixel.groupSyncReadTxRxPacket(groupread_num)
        if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
            dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))

        # Check if groupsyncread data of Dynamixel#1 is available
        dxl_getdata_result = ctypes.c_ubyte(dynamixel.groupSyncReadIsAvailable(groupread_num, DXL_ID, ADDR_PRO_INDIRECTDATA_FOR_READ, LEN_PRO_PRESENT_POSITION)).value
        if dxl_getdata_result != 1:
            print("[ID:%03d] groupSyncRead getdata failed" % (DXL_ID))
            quit()

        # Check if groupsyncread data of Dynamixel#2 is available
        dxl_getdata_result = ctypes.c_ubyte(dynamixel.groupSyncReadIsAvailable(groupread_num, DXL_ID, ADDR_PRO_INDIRECTDATA_FOR_READ + LEN_PRO_PRESENT_POSITION, LEN_PRO_MOVING)).value
        if dxl_getdata_result != 1:
            print("[ID:%03d] groupSyncRead getdata failed" % (DXL_ID))
            quit()

        # Get Dynamixel#1 present position value
        dxl_present_position = dynamixel.groupSyncReadGetData(groupread_num, DXL_ID, ADDR_PRO_INDIRECTDATA_FOR_READ, LEN_PRO_PRESENT_POSITION)

        # Get Dynamixel#2 present position value
        dxl_moving = dynamixel.groupSyncReadGetData(groupread_num, DXL_ID, ADDR_PRO_INDIRECTDATA_FOR_READ + LEN_PRO_PRESENT_POSITION, LEN_PRO_MOVING)

        print("[ID:%03d] GoalPos:%d  PresPos:%d  IsMoving:%d" % (DXL_ID, dxl_goal_position[index], dxl_present_position, dxl_moving))

        if not (abs(dxl_goal_position[index] - dxl_present_position) > DXL_MOVING_STATUS_THRESHOLD):
            break

    # Change goal position
    if index == 0:
        index = 1
    else:
        index = 0

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 goal position dxl_goal_position and LED value dxl_led_value to the syncwrite target Dynamixel list.

groupSyncWriteTxPacket() function sends an instruction to the Dynamixel #DXL_ID through the port, making it possible to write same pre-listed length bytes to same pre-listed address. The function checks Tx/Rx result. getLastTxRxResult() function get 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.

groupSyncReadTxRxPacket() function sends an instruction to the Dynamixel #DXL_ID through #port_num port, making it possible to read same pre-listed length(LEN_PRO_INDIRECTDATA_FOR_READ) of bytes to same pre-listed address(ADDR_PRO_INDIRECTDATA_FOR_READ). 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.

groupSyncReadIsAvailable() function checks if available data is in the groupsyncread data storage. The function returns false if no data is available in the storage.

groupSyncReadGetData() function pop the data received by groupSyncReadTxRxPacket() function out. In the example, it stores LEN_PRO_PRESENT_POSITION byte data and LEN_PRO_MOVING byte data got from ADDR_PRO_INDIRECTDATA_FOR_READ address of Dynamixel.

groupSyncReadClearParam() function clears the Dynamixel list of groupsyncread.

Reading their present position will be ended when absolute value of (dxl_goal_position[index] - dxl_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 Torque
dynamixel.write1ByteTxRx(port_num, PROTOCOL_VERSION, DXL_ID, ADDR_PRO_TORQUE_ENABLE, TORQUE_DISABLE)
if dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION) != COMM_SUCCESS:
    dynamixel.printTxRxResult(PROTOCOL_VERSION, dynamixel.getLastTxRxResult(port_num, PROTOCOL_VERSION))
elif dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION) != 0:
    dynamixel.printRxPacketError(PROTOCOL_VERSION, dynamixel.getLastRxPacketError(port_num, PROTOCOL_VERSION))

The controller frees the Dynamixel to be idle.

write1ByteTxRx() function sends an instruction to the #DXL_ID Dynamixel in PROTOCOL_VERSION communication protocol through #port_num port, writing 1 byte of TORQUE_DISABLE value to ADDR_PRO_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
dynamixel.closePort(port_num)

Finally, port becomes disposed.