Tuesday, November 19, 2019

What is serial communication?

In order to understand communication protocols we first need to understand digital systems. A digital systems communicates a message in the form of binary information. This is a flow of digital pulses sent from one point to another creating a means of data transmission.

Serial communication is a widely used medium to transfer information between various different equipment and peripherals. Data is in the form of sequential binary pulses. Binary can be represented in two states i.e: a one (1) represents a logic high or "on" status and a zero (0) represents a logic low or "off" status. 

The different modes of transmitting data over serial communication
  • Simplex transmission is a one-way communications method, with only one client present on the network. if a sender engages in transmission then a receiver is only able to accept information. examples: Radio and television transmission. 
  • Half Duplex mode have both an active sender and a receiver, however these can not be active at the same time.  if a sender transmits information then a receiver will accept, but can not transmit and vice-versa. A good example of this is PROFIBUS DP networks, these communicate over serial copper mediums (not exclusively) and when a master device communicates to slave stations, the slave will stay silent until the master has concluded the message transmission, once this is completed then the slave station will respond with the requested information.
  • Full Duplex mode is widely used when high speed transmission is required in serial communication. Both the sender and receiver can communicate at the same time as there are dedicated cable cores for transmitting and receiving data. Transmission over RS232 utilises full duplex transmission methods.

How the serial communication gets created and generated

Serial communication on a hardware level can be simply explained through the use of a micro processor and a UART (Universal Asynchronous Receiver Transmitter). The micro processor composes information and sends this in the form of bytes to the UART, which then sends this information out in a series of bits. 

The data sent out from the UART is classified as a serial frame and is arranged in a specific sequence. It comprises of a start bit, some data bits and a stop bit.

Some important factors for successful serial transmission of data
  • Baud rate which is the speed at which data bits are transferred between the transmitter and the receiver, this speed needs to be configured the same for both nodes. The transfer speed is usually specified in bits per second. There are various standard baud rates: 1200, 2400, 4800, 9600, 19200, 38400, 57600 +. PROFIBUS can run up to 12582912 bps, which is very fast for  a serial bus running over a copper medium.
  • Data bits is the number of bits composed into the serial message fame, usually 7 or 8.
  • Parity is an error checking bit used to make the message frame even or odd. The parity bit provides the receiver with  a mechanism to determine if the frame has been corrupted or changed during transmission, for example by interference from high voltage cabling running close to your serial data lines.

Some important factors for the successful use of the serial data systems
  • Understanding the protocol - Protocols and standards are what make networks and devices work together successfully. Protocols have rules set in place to enable effective communication to occur. Attending training with a protocol expert can help to bring the blurred lines into focus.
  • EndiannessWhen designing computers and embedded devices, there are two different architectures for handling memory storage. They are called big-endian and little-endian and refer to the order in which the bytes are stored in memory, i.e. Most significant bit is consumed first (big-endian), or least significant bit is consumed first (little-endian). Windows NT was designed around little-endian architecture and was not designed to be compatible with big-endian because most programs are written with some dependency on little-endian. Some protocols however require big-endian format e.g. PROFIBUS DP.
  • Data storage - There are various memory location within a serial network, the common areas are input and output memory. Serial networks are used by a number of protocols and it is essential to note the data storage and bit transfer sizes allowable on these specific networks. Considerations for memory location, memory start address, data types and length are critical for the successful use and implementation of serial communication systems.
  • Checksum - Most serial protocols features some way of verifying that the data has not been corrupted during transfer. A checksum is the result of running an algorithm on a piece of data, also known as cryptographic hash function. Comparing the checksum data received with the algorithmic equivalent for that piece of data will determine if this data is genuine and can be used or if the data has errors and should be rejected. Checking for checksum errors on your serial networks, or CRC errors is a useful way of determining if there is some underlying fault that is reducing the network health and availability. Any errors should investigated and faults corrected.

Have a serial / Ethernet network related query, require assistance with or training on your communications systems? Chat to one of our Engineers at IDX technical solutions:

Email:      info@idx.co.za
Contact:   +27 11 548 9960
Web:        www.idx.co.za

Tuesday, April 23, 2019

IDX at Africa Automation Fair 2019

JOIN IDX at the African Automation Fair

IDX in association with Reed Exhibitions invites you to join us at the Africa Automation Fair on the 4th - 6th June 2019 at the Ticketpro Dome.

IDX will be giving away the following to a few lucky individuals at the Africa Automation Fair

  • Free training vouchers for our earthing, IIoT and product specific course
  • Free PROFIBUS Network Audit (1 day travel dependent) by a Certified PCC PROFIBUS Engineer

For more information on our training course, Click HERE
IDX will be showcasing the following products:

IDX Nexus – Data Harvester

Connects disparate systems on heavy mobile machinery and other high value assets, allowing you to share real-time data between on-board systems. Compatible with common protocols such as Modbus, CAN, J1939, OPC, ASCII and more. You can log your machine data locally or transfer it in real-time to a remote server for use in real-time data systems or simply store it for trending and analysis. 

ESTABLISH connections, MAINTAIN connectivity & LEVERAGE data to work for you!

The PROCENTEC Mercury is out now!

With Industry 4.0 in mind, the Mercury accounts for mixed architecture facilities that incorporate older networks as well as Industrial Ethernet networks. 
This all-in-one mobile analyser gives you the ability to troubleshoot, maintain and monitor both PROFIBUS and Industrial Ethernet networks.

A robust tablet running the new software package (OSIRIS) offers remote and wireless connection capabilities providing you with an easy-to-interpret solution that offers mobility from anywhere.

Meet the Revolution Pi

Revolution Pi is an open, modular and inexpensive industrial PC based on the well-known Raspberry Pi. Packaged in a slim DIN-rail housing, the three available base modules can be seamlessly expanded with a variety of suitable I/O modules and fieldbus gateways.

The 24V powered modules are connected via an overhead connector in seconds and can be easily configured via a graphical configuration tool.

Harness the power of your data

Anybus IIoT solutions allow the integration of industrial systems to IIOT platforms supporting MQTT and OPC-UA. Experience a transformation in manufacturing, increase efficiency and enable predictive maintenance. The X-gateway now enables seamless connections with control systems and their connected devices to this IIoT system, whilst the Communicator connects non-networked industrial devices and equipment based on serial and CAN communication to the IIot system.

Click here to Register to visit

For more information on any courses please contact IDX on the below. 
www.idx.co.za | academy@idx.co.za | 011 548 9960

Wednesday, February 27, 2019

ProfiHubs with diagnostic capabilities

Network downtime getting you down?

Introducing PROCENTEC’s range of ProfiHubs, now with new diagnostic capabilities!

The diagnostic ProfiHub is a versatile statistics / diagnostics logger that can be used to keep track of the overall network health and inform either the PLC or DCS of any network failures. These network failures could be in the form of repeated messages, illegal messages, missing ProfiHub terminations, live list changes or power supply problems. Audible or visible feedback can also be achieved by switching the integrated alarm relay of the ProfiHub.

All ProfiHubs are now shipped with this functionality available as standard. Existing ProfiHub owners will soon be able to purchase upgrade packages to enable the diagnostic capabilities via a firmware update. The diagnostic capabilities are available for the B2+R, B5+R, D1, B2FO2, & B4FO2 and these hubs are fully compatible with PROCENTEC ComBricks providing you with a permanent monitoring solution that lets you troubleshoot your network down to the last segment. 

You can use ComBricks to display the most important diagnostics of every channel. This information can be accessed through the webpage of the connected ComBricks unit and the information is displayed as follows:

The information displayed includes the address, tag name, type, serial number and firmware version of the diagnostic slave, the connection (network, module and channel number) of the ComBricks, the redundancy and power status of the ProfiHub, the termination status, illegals and a live list of all channels and the alarm status (of the relay).

The diagnostic data is sent over PROFIBUS so the information can be easily read using the ProfiTrace software. Maintenance engineers can immediately identify the affected segment in the case of cable faults or instrument failure, which drastically decreases downtime.

The events and statistics in the table above are continuously monitored and can be transferred in the following ways so that a PLC / DCS user can be warned of any network issues that may arise:

For more information visit: https://www.idx.co.za/Protocols/PROFIBUS/Network-Components/Repeaters-Hubs

Visit the demo environment at http://combricks.idx.co.za/ to see how the diagnostic ProfiHubs can be integrated with ComBricks.

Feel free to contact the IDX team for additional details or more information on any of the topics mentioned above.

E-mail: info@idx.co.za
Phone: +27 11 548 9960 

Friday, February 22, 2019

Anybus gateway's creating secure paths for IIOT solutions

Anybus has launched a new family of gateways built to boost your Industrial IoT development demands. These devices are designed to gain secure and easy access between equipment on all major industrial networks, transforming the way your industry, manufacturing business, process factory or packaging plant operates by improving visibility. Now you can establish a foundation for better performance by leveraging this data.

The Anybus IoT X-Gateways and Communicators lets you seamlessly interconnect legacy devices and PLC control systems between industrial networks and OPC UA/MQTT. The information is controlled independently and your network remains secure and encrypted.

How does it work?

The Anybus IoT Communicator, still based on the tried and tested communicator development, will now enable users to integrate serial based RS232, RS485, Modbus RTU, DF1 and ASCII into an OPC UA or MQTT IoT data acquisition system. 

Simply connect, configure and your done!

Mount and power your device with 24VDC +-10%. Connect the device to the related two networks.

Configuration for Communicators:
  1. Configure the Industrial network side (serial side) by connecting the device to your computer via its Rj11 port (a serial to Rj11 cable is provided with your device). You may need a serial to usb converter, this can be easily obtained from your local computer accessory supplier.
  2. Download and install the free Anybus Configuration Manager software for communicators, run this software and configure the data registers or telegrams according to the device/s connected to this network (serial side). 
  3. You are required to set an IP adress for the device (IIoT side), this can be done through the use of free software provided by Anybus called IP Config tool. Connect your device to your computer through its Rj45 connection points with an Ethernet cable. run the IP Config software and run a scan, once you find your device then reassign the IP address as required. 
  4. Now configure the IIoT side through the use of its web interface and free software provided by Anybus. Download and run the Configuration manager tool for IIoT, select the type of IIoT platform you would like to use (MQTT or OPC UA) and add your tags/topics. Once this is done generate and send the config to the communicator.
  5. You can now configure the IIoT details within the web interface. log into this by inputting the IP address of the communicator into your web browser.

Configuration for X-gateways:
  1. Set the the IP address of the IIoT side by connecting your gateway to your computer via an Ethernet cable. Through the use of the IP config software provided by Anybus, scan and change your IP address as required.
  2. Configure the industrial network side by connecting your gateway to your computer via the USB cable provided. Run the Anybus Configuration manager tool for X-gateways and configure the data sizes required for your application.
  3. follow steps 4 and 5 listed above.
OPC-UA available options
  1. OPC-UA discovery server
  2. OPC-UA TCP port
MQTT available options:
  1. Broker URL
  2. Client identifier
  3. Keep alive time (s)
  4. Broker username
  5. Broker password
  6. Base topic
  7. QoS (Quality of Service)

Feel free to contact the IDX team if you would like to find out more details on any of the topics mentioned above:

+27 11 548 9960

Monday, February 11, 2019

PROFIBUS wiring error / B-line short

 PROFIBUS wiring error / B-line short

IDX attended a PROFIBUS call out for a gold mine situated in Welkom.
The client reported issues as “loss of communication and network trips”.

Using the PROCENTEC Mercury Pro Kit (A complete diagnostics tool for troubleshooting PROFIBUS and Industrial Ethernet Networks) we were able to identify the underlying issue as a short between the B-core (red wire) and the PROFIBUS cable shield.

The short in the PROFIBUS cable meant that the differential signal was significantly lower in amplitude and therefore more susceptible to earthing faults and EMI injections on the bus.
PROFIBUS makes use of a balanced signal. This means that the signal transmitted on the A and B channels have similar voltage levels, however, they have opposite polarities. The differential signal is calculated as B – ( – A).

When a short occurs on the PROFIBUS cable between either of these cores and the PROFIBUS cable shield, the shorted core will produce a flat line and the resultant differential signal will effectively be halved.
This balanced communication method, also helps to combat any noise that may be picked up on the network. The assumption is that any interference injected on the bus will be picked up on both the A and B channel which, when combined, will result in a clean differential signal.
PROFIBUS network was still running on a single core, the interference injected onto the network when certain machines or drives were started, was enough to cause communication issues and intermittent network trips.

An oscilloscope that is able to display the individual signals of each of the cores is necessary to effectively identify a “short to shield”. Both the Osiris software (Mercury Pro Kit) and the ProfiTrace software (PROFIBUS Troubleshooting Tool Kit) have this functionality built in.

By enabling the terminating resistors at certain points on the segment, we could pinpoint the exact location of the fault and replace the faulty cable.
After limited down-time for the repair work to take place, we had the network up and running. Oscilloscope measurements taken after the fault had been rectified confirmed a healthy PROFIBUS signal on both A & B channels and in turn, a much more robust differential signal.
No network trips have since been reported.
Maintaining your existing connections, in this case maintaining a healthy PROFIBUS network, is the responsibility of the on-site technical team.
As with anything, the necessary knowledge and the right tools for the job are required to ensure that your production is not affected.

Simply IDX it! If you’re looking for certified industrial communications protocol training, if you want to become a certified PROFIBUS installer and work your way up to a certified PROFIBUS engineer, if you’re looking for troubleshooting kits or permanent monitoring for your network, contact us and we’ll provide a solution.

Feel free to contact the IDX team if you would like to find out more detail on any of the topics mentioned above:

+27 11 548 9960

Thursday, January 31, 2019

How to achieve high PROFIBUS network availability

The difference between three 9's (9.99%) and four 9's (99.99%) availability on your PROFIBUS communications network could mean millions of Rands in lost production that directly affects your bottom line.
Network rigidity and availability should be the core focus of any automation engineer who is tasked with maintaining a plant's PROFIBUS communication system.

There are four main areas to focus on that will assist in improving your 9's score on any given network:

1) Training

Fundamentally important, ensuring that all personnel who work with the network have the necessary training and know-how. Your local PROFIBUS / PROFINET Training Center will have a set of certified courses to ensure that all attendees are competent to handle installations and design scenarios. The following courses should be considered for PROFIBUS networks:

  • Certified PROFIBUS Installers Course
    • Foundation PROFIBUS Training Course, imparts knowledge on the PROFIBUS specifications, installation guidelines and necessary network components.
    • This course should be attended by EVERYONE who works on / with a PROFIBUS network (plant automation engineers, artisans, cable installers, system integrators & even management responsible for plant production and uptime)
  • Certified PROFIBUS Engineers Course
    • More advanced PROFIBUS training that goes into detail on the PROFIBUS Specification, FDL analysis and advanced troubleshooting and maintenance procedures. PROFIBUS engineers are equipped to carry out network audits and conduct advanced analysis on the system. 
    • Persons responsible for troubleshooting, design and maintenance of PROFIBUS networks would benefit substantially from this course.
  • Certified PROFIBUS PA Engineers Course
    • Builds on top of the standard Certified PROFIBUS Engineers Course, giving advanced protocol specific details on PROFIBUS Process Automation (PA). Being a very hands-on course, attendees will set up a PA segment and learn advanced design, analysis and troubleshooting techniques.
    • Persons responsible for troubleshooting, design and maintenance of PROFIBUS PA networks would benefit from this course.
  • Certified PROFIBUS System Designer Course
    • Learn best practices for any industrial automation network, including PROFIBUS, Industrial Ethernet and lower level protocols such as AS-I. Achieving high network availability is discussed in detail as well as a big focus on the necessary parts and components to achieve this.
    • Persons tasked with designing, implementing and maintaining industrial automation systems would benefit substantially from this course. This course is not just limited to the PROFIBUS protocol, as most industrial fieldbus and Ethernet systems work in a similar way.

2) Network Audit

A competent certified PROFIBUS engineer can evaluate each element of your installation, ensuring that all parts comply with the latest PROFIBUS installation requirements. On completion of the system evaluation, an audit report with all recommendations and fixes completed will be issued by the PCC (PROFIBUS / PROFINET Competence Center). Should the installation be found to fully meet the requirements, a report of compliance will be issued from the Competence Center.
A comprehensive network audit will give an insight into all the problem areas within your PROFIBUS system. A scheduled network audit is an extremely effective way of preventing breakdowns and downtime from occurring, unnecessarily costing industry inordinate amounts each day. If you have a network audit carried out, this will ensure that your network gets back to the correct level of quality.

Some of the benefits that can be realized from an effective network audit include:

  • A reduction in downtime and the associated lost production and costs
  • Receiving detail on network EMI interference, risk and corrective action
  • Detailed reports issued with specific recommendations
  • A proactive approach to ensuring your network is resilient against any interference
  • Ensuring contractor installations meet PROFIBUS international guidelines
  • Receiving detailed information on network design and expansion

  • You can contact your local PCC for a list of Certified Competent PROFIBUS & PROFINET engineers to assist you with a professional network audit. 

    3) Network Testing Tools

    PROFIBUS is often referred to as a 'hardware based protocol', thus it is crucial to have the necessary testing and assessment tools to assist you in fault finding, preventative maintenance and ensuring you have high network availability overall.

    Cable Tester
    A cable tester will check the integrity and correctly implemented wiring of the cable before commissioning, ensuring that there are no wiring issues such as short circuits, open circuits, missing terminations, breaks in shield continuity, etc.

    Bus Analyser
    All users responsible for the maintenance and upkeep of an active PROFIBUS network should have access to a reliable and powerful bus analyser. A bus analyser is a hardware and software conglomerate that can read all telegrams being transmitted on the bus and generate key summary statistics of the bus operations. The analyser should also be able to measure and feedback an electrical analysis of the bus signal utilizing an integrated oscilloscope.

    Your testing tool should support the following requirements:
    • Live list overview, showing an overall health of each PROFIBUS node
    • Message recording and reporting functionality
    • High performance bus statistics with a summary view
    • Advanced oscilloscope with differential and split signal view
    • Bar graph showing all driver voltages, including a varying high and low view
    • Network topology detection and cable length measurement
    • PROFIBUS master simulator - allowing active network configuration by utilizing its built-in GSD file database

    The above specifications are based on the PROCENTEC PROFIBUS Troubleshooting Kit Ultra Pro

    For more information on useful testers for PROFIBUS, you can visit the following blog:

    For detailed specifications, please see our page for a full list of tools:

    4) Permanent Monitoring for preventative maintenance

    Implementing an early warning detection system should be able to alert users to potential faults prior to it creating a failure. Permanent monitoring solutions also monitor the network 24/7 and can provide a network engineer with the critical data and statistics needed to effectively correct any intermittent faults and faults occurring outside of maintenance shifts.

    The entire infrastructure and architecture of your network should be able to feedback error statistics and possible risks to higher level notification systems.
    An example of this infrastructure may be a SCADA that receives network diagnostic information from lower level infrastructure such as diagnostic repeaters.

    For critical systems and processes it is necessary to install an advanced permanent monitoring solution such as ComBricks. ComBricks is a modular, permanent monitoring solution for PROFIBUS networks. Each module can repeat to alternate channels to allow for full integration within the network architecture.
    Each module has an integrated oscilloscope and ties into Procentec's ProfiTrace framework to allow for in depth signal, message and statistic analysis.
    ComBricks transfers the data to the user through an on board web interface which can be accessed through the plants existing Ethernet infrastructure, additionally, it can email users on certain risk thresholds being reached.

    Feel free to contact the IDX team if you would like to find out more detail on any of the topics mentioned above:
    +27 11 548 9960

    Wednesday, January 30, 2019

    Common pitfalls when installing a Modbus RS485 network on site

    Last week IDX were called to site at a large commercial residence building in Pretoria, South Africa. Where our client was implementing an IoT solution for remote monitoring and control of various HVAC and power systems in the building. The control system the SI chose in this case was a Modbus enabled Industrial Micro PC called the Revolution PI.
    The client had Modbus sensors connected to boilers, air conditioning systems, ventilation systems and power meters.

    The Modbus communications between the controller and the sensors were intermittently failing due to various installation and implementation faults:

    1. Earthing and Shielding

    Within any fieldbus communication installation, one of the requirements to ensure uninterrupted operation is to implement adequate grounding and shielding techniques. Effective grounding and Shielding help to prevent electrostatic and electromagnetic pickup, which can lead to failed communications.

    Some of the shielding and grounding requirements for a Modbus RS485 Network:

    • Utilising twisted shielded serial cable (120Ω impedance)
    • Ensuring continuity of the shield across the entire segment
    • Grounding the shield at multiple points (preferably at each device)
    • Ensure devices are properly grounded to an appropriate functional earth within cabinets
    • Running a potential equilisation cable between cabinets where necessary

    Fig.1 No grounding / shield continuity
    The shield surrounding the communication wires will transfer any picked up noise or interference and drain it to ground. It is important to ground the shield as you enter and exit cabinets and at each device, this provides the shortest path to ground for any interference picked up on the network.

    What we found on site (Fig.1)

    1. No continuity of the cable shield
    2. No grounding of the shield within the cabinets or devices
    3. No functional earthing of devices within the cabinets

    2. Running Modbus cable close to high voltage cabling

    High voltage cable and machinery can interfere with bus communications, they do so by electrostatic and electromagnetic injection.
    One way to avoid this interference / injection on the bus is to separate your communication cable from the source of interference.

    The adequate separation distances between the communication cable (Category 1) and any high voltage cables / devices (Category 2,3 & 4) is displayed below (Fig.2).

    • Category 1 
      • Fig.2 Cable separation diagram
      • Modbus cable, LAN cables, < 25VAC, < 60VDC
    • Category 2
      • AC: 25V - 400V
      • DC: 60V - 400V
    • Category 3
      • AC & DC: >400V
    • Category 4
      • Cable at a risk from lightning strikes (e.g. cables running between buildings)

    What we found on site (Fig.3 & .4)

    Fig.3 Violation of cable separation requirements
    1. Running close to 400 VAC cables
    2. Severe noise injected on the signal bus
      • Within Figure 4 you can see two scope lines (red and green), this is your B & A lines respectively.
      • RS485 is a balanced  system and carries the same signal on both line A & B, however the exact inverses of each signal on each line. Thus any noise that is picked up should cancel out once the signal is combined.
      • This scope was taken on a Modbus installation that was silent and indicates poor implementation of RS485 protection mechanisms.
    3. Little protection from EMI due to poor earthing and shielding techniques implemented

    Fig.4 |EMI picked up on the Modbus cable due to poor shielding and
    exposure to high voltage cables

    3. Missing end terminators

    Fig.5 Installed 120Ω resistor and implemented grounded shielding
    Reflections on a fieldbus cable are caused by an impedance mismatch. One of the major contributing factors causing reflections, is at the end of the fieldbus line where the signal waveform 'bounces back' towards to transmitter and disrupts consecutive signals on the bus (Fig.6).

    To prevent these reflections, you can absorb the signal waveform at the end of each line within your Modbus network by installing a 120-ohm resistor at the beginning and end of the segment.

    As segment lengths are increased, the effect of reflections without effective terminating resistors installed becomes more severe.
    Fig.6 Normal operation (left) vs Missing termination (right) scope image

    Should you seek consulting or professional engineering services to assist you in achieving high network availability on your Modbus installation, then contact IDX Technical Support:
    +27 11 548 9960

    IDX also offers a one day Modbus overview course which covers Modbus RTU, ASCII & TCP. For more information on this course please visit our training page: