Communications

The Nix Servo Drive provides the following network communication interfaces for configuration and operation:

All the interfaces can be used to connect the Nix with Ingenia Motion Lab suite or a custom application built with the supplied controller libraries. With the objective of configure and diagnostic CAN communication, CANopen and another communication interface can be used simultaneously.

USB interface

Nix Servo Drive supports Universal Serial Bus (USB), a standard interface for connecting peripheral devices to a host computer. The following table shows main USB interface specifications:

Specification

Details

USB version

USB 2.0 (full speed)

Data rate

Up to 12 Mbps

Maximum cable length

5 meters (16 feet)

USB application

USB interface is only recommended for configuration purposes. For noisy environments, CANopen interface is strongly recommended.

USB powered drive

The Nix can be powered from USB for configuration purposes without the need of an external power supply. With USB supply the Nix is not capable of driving a motor, but communications, feedbacks and IOs are fully functional. An internal switch automatically chooses the power source prioritizing the Supply and shunt connector. Please note that several functionalities will not be available when powered from USB.

USB wiring recommendations

Although USB is a widespread communication standard it has some disadvantages when operating in noisy environments. Following are some wiring recommendations. 

  • Use shielded cable with the shield connected to PC end. Shield of micro USB connector is not connected on Nix. 
  • Do not rely on an earthed PC to provide the Nix Servo Drive earth connection. The drive must be earthed through a separate circuit.
  • Avoid creating ground loops by using isolated power supplies.
  • Shortest cables are preferred. 

USB EMI sensitivity

USB is not a rugged interface, and is sensitive to EMI. For the NIX-5/170 use a good quality cable shorter than 1 m to avoid communication problems while the power stage is enabled.

RS485 interface

Nix Servo Drive supports full duplex RS-485. This means that independent differential lines are used for TX and RX, which cannot be connected together. Full-duplex RS485 is fully compatible with RS422 communication.  

Multi-point connection

Nix Servo Drive RS485 interface is not intended for bus operation, since there is no collision prevention protocol implemented. However, multiple drives can be connected to the same master using daisy chain connection.

Multiple drive connection with daisy chain must be configured using Ingenia Motion Lab suite. For allowing multi-point communication each servo drive must be allocated a unique node ID, and daisy chain option must be enabled. Please, see UART configuration section in E-Core documentation for further information.

Main specifications of Nix RS485 interface are shown in the next table:

Specification

Details

InterfaceFull duplex
Non-isolated
Self-supplied (no need for external supply) 

Communication distance

Up to 1200 m

Baud rate

100 kbps to 10 Mbps

Daisy chain

Supported

Termination resistor

Nix version 1.1.0: 120Ω on RX line included.

Nix version 1.2.0 (Release Feb 2017): Resistor 120 Ω on TX and RX lines included.

Next figure illustrates how to connect Nix Servo Drive with a host in a point to point configuration.

NixRS485point-to-point

Termination resistor

The use of termination resistors at the RX side of each differential pair (120 Ω between RX+ and RX- of both host and slave) is essential for correct operation of the RS485 communication. For long cable distances (> 10 m) a termination in the TX side is also recommended.

Nix Servo Drive version 1.1.0 includes a termination on the RX terminals. Therefore, a 120 Ω termination resistor should be placed at the end of Nix TX line (RX of the host). Nix Servo Drive version 1.2.0 includes a termination on the TX terminals too.

Suggested termination resistor: Xicon 271-120-RC.

Multi-point connection using daisy chain

Daisy chain connection is a multi-point network topology based on connecting multiple terminals in a ring. The wiring consists on connecting the TX terminals of each device to the RX terminals of the next device. An example of daisy chain wiring of multiple Nix is shown in the next figure. 

NixRS485Multiple

Termination resistor for daisy chain

In daisy chain connection, termination resistors are required in each link. For short distances, a 120 Ω termination resistor in the RX side is required. For long distances (> 10 m) a termination is required in RX and TX sides.

Nix version 1.1.0 includes a termination on the RX line allowing direct daisy chain wiring for short links. Nix Servo Drive version 1.2.0 includes a termination on the TX terminals, allowing direct daisy chain wiring for long distances.

Daisy chain clever wiring with flat cable

The Nix Servo Drive RS485 connector allows to implement a daisy chain using flat ribbon cable. This solution highly simplifies the wiring.

Note that for short distances, the flat ribbon cable with characteristic 100Ω ~ 120Ω line impedance provides good physical layer for RS485. For long distances preferably use twisted pair cable.  

NIX-RS485DaisyChainWiring

CANopen interface

Nix Servo Drive supports CANopen interface, a multi-terminal communication protocol based on CAN (Controller Area Network) bus. Nix CAN interface is isolated, and self-supplied. Main physical specifications are shown in the next table:

Specification

Details

InterfaceNon-isolated
Self-supplied (no need for external supply)

Baud rate

From 125 kbps to 1 Mbps (default value)

Maximum number of nodes

64

Common mode voltage

Up to 48 V

Termination resistor120 Ω on board (mount jumper to enable the termination)

Drive ID

When installing CANopen communication, ensure that each servo drive is allocated a unique ID. Otherwise, CANopen network may hang.

An example of CAN wiring is shown in the next figure.

NixCANbus

Termination resistor

The use of bus termination resistors (120 Ω between CAN_L and CAN_H), one at each end of the bus, is essential for correct operation of the CAN bus. Even with only one Nix connected, mount the termination resistor to ensure CAN bus operation. Do not use wirewound resistors, which are inductive.

Nix Servo Drive includes a termination resistor on board. A jumper placed next to the CAN connector allows the user to connect or disconnect the 120 Ω termination resistor. Use a standard 1.27 mm pitch jumper for this purpose.

NixCANJumper

CAN GND connection

GND line in CAN devices is used for equaling potential between master and slaves, but is not used for data transmission, as the line is fully differential. For this reason, if the host device shares supply GND with Nix it is not needed to connect CAN connector GND again, as this could cause ground loop issues.

If power supplies are isolated and flat ribbon cable is used, it is preferred to connect both GND connector pins (1 and 4), equaling the signal to GND impedance.

CAN interface for PC

The Ingenia Motion Lab suite is able to communicate with the Nix Servo Drive through CANopen interface. For this purpose, a CAN transceiver for PC is required. Motion Lab is compatible with the following CAN transceivers: Kvaser, Peak-System, IXXAT, Vector and Lawicel. Please, install the drivers you can find on the manufacturer web sites before, plugging any transceiver to the USB port. Execute Motion Lab only after the device is already installed. 

Some recommended CAN transceivers are shown below:

ManufacturerPart NumberImageDescription
Peak-systemPCAN-USB opto-decoupled (IPEH-002022)

  • USB to CAN single channel interface with 9-pin D-SUB CAN connector.
  • Enables simple connection to CAN networks.
  • Opto-decoupled with galvanic isolation of up to 500 Volts between the PC and the CAN side.
KvaserUSBcan Pro 2xHS v2

  • USB to CAN or CAN FD dual channel interface.
  • High-speed CAN channels in two separate 9-pin D-SUB CAN connectors.
IXXATUSB-to-CAN V2 Professional

  • USB to CAN dual channel interface.
  • High-speed CAN channels in two separate RJ-45 connectors.
  • Cable adapter to 9-pin D-SUB CAN.
Vector InformatikVN1630

  • USB to CAN or CAN FD four channel (two connectors) interface .
  • High-speed CAN channels in two separate 9-pin D-SUB CAN connectors.
  • Highly robust plastic housing.

CAN wiring recommendations

  • Build CAN network using cables with 2-pairs of twisted wires (2 wires/pair) as follows: one pair for CAN_H with CAN_L and the other pair for CAN_V+ with CAN_GND. 
  • Cable impedance must have an impedance of 105 to 135 Ω (120 Ω typical) and a capacitance below 30 pF/meter.
  • Whenever possible, use bus links between the CAN nodes. Avoid using stubs (a "T" connection, where a derivation is taken from the main bus). If stubs cannot be avoided keep them as short as possible. For maximum speed (1 Mbps), use a stub length lower than 0.3 meters.
  • For a total CAN bus length over 40 meters, it is mandatory to use shielded twisted cables. Connect the cable shield to protective earth at both ends. Ensure that the cable shield is connected to the connector shield, as connection to host protective earth is usually soldered inside the connector.

EtherCAT interface

Nix Servo Drive with EtherCAT (NIX-x/xx-E-z) variant provides access to the EtherCAT fieldbus system. EtherCAT is an isolated bus suitable for hard and soft real-time requirements in automation technology, test and measurement and many other applications. 

Next table summarizes the features of the Nix EtherCAT interface.

EtherCAT specific features

Ports available

2

LED SignalsStatus LED
Link/Act LED

Supported Mailbox

CoE

SDO info

Not supported

Segmented SDO

Supported

SDO complete access

Not supported

Synchronization modesFree Run

Distributed clock (Cyclic modes)

Process data object

Configurable, up to 64 objects

Next figure shows a wiring diagram of an EtherCAT bus.

NixEtherCATbus