Rethink IO-Link Components Selection: Start with the Devices, Not the Gateway/Master
Most people approach IO-Link component selection in the wrong order by starting with the Gateway/Master.
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Most people approach IO-Link component selection in the wrong order, starting with the Gateway/Master. A smarter approach is to think backward – begin with the IO-Link devices that fit your application.
The three key components of an IO-Link system
An IO-Link system typically consists of the following components, in the order most people discuss them:
The IO-Link Gateway/Master unit is a device that converts the IO-Link protocol/packets into the upper-level protocol/packets like EtherNet/IP, Profinet, EtherCAT or Modbus TCP.
IO-Link devices are intelligent devices that connect to the Gateway/Master and provide process data in engineering units, as well as higher-level diagnostics and warning/error events.
Standard Sensor/patch cables (M12-to-M12) typically connect IO-Link devices to the Gateway/Master.
Where to start and why
Are these components easy to choose? Yes, but only if we take the time to plan our architecture carefully. Now, let’s revisit the three components, this time in a different order of priority.
1. IO-Link devices – start here! Your IO-Link implementation begins with the devices required for your application. Once you’ve identified these, they will dictate your cable and Gateway/Master selection.
2. Standard Sensor/Patch cables. Your choice of cables depends on the pinout and connector style of the IO-Link device. Consider these two factors:
Connector style – Even though many IO-Link devices use the M12 style of connectors, some require M8 and M5 connectors.
Number of conductors – While many of us focus on the general terms of IO-Link and use three conductors for IO-Link communication, others on the market require four or even five. Class A devices may need three or four conductors, and Class B devices need five.
Before purchasing cables, ask your IO-Link device vendor to confirm the device's port pinout.
3. IO-Link Gateway/Master – choose last! Why might this be the last component to choose? It's easy – at this stage, you know what IO-Link devices and cables your application requires. You will also determine the necessary cable specifications, including the number of conductors and whether Class A or B ports are needed.
With this information, you can narrow your selection to the appropriate Gateway/Master. At this point, you need to determine what you require.
A Master with all Class A ports (keeping in mind that not all Class A Gateways/Masters use Pin 2 of the IO-Link port for output).
A Gateway/Master with all Class B ports
A Gateway/Master with a mix of Class A and B ports.
Once you’ve determined these factors, you can ask your Gateway/Master vendor to find the correct part number that meets these requirements, including the necessary upper-level network protocol (EtherNet/IP, Profinet, EtherCAT, etc.) and IO-Link port styles. Luckily, many IO-Link Gateway/Masters now support multi-protocol communication, so one part number can communicate on multiple networks.
My advice: Take your time. First, pick your IO-Link devices. Next, determine the required cables. Finally, choose the Gateway/Master that provides the needed IO-Link ports and network protocols.
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