Start with this checklist if the PLC has a blinking red error lamp and you suspect an IO-Link fault.
- Verify that access rights for each port are returned to PLC control.
- All field devices are connected to the IO Link master(s).
- Each field device is connected to the assigned channel.
- TIA Portal’s IO-Link master submodules are properly assigned.
Note: Log into the SIG300 using a USB cable and then point a browser to 169.254.0.1.
Figure 1: Hardware used for the IO-Link troubleshooting along with a Siemens comms error.
Access Rights Errors in the IO-Link Master
Incorrectly configured access rights are a painful source of self-induced errors. As part of troubleshooting we log into the IO-Link master, change the port to local control and then forget to return control back to the PLC.
For example, consider the SICK SIG300 Profinet IO-Link Master. The access rights are shown in Figure 2. The last four boxes in the first column must be selected for unrestricted PLC access.
Figure 2: Image of the SICK SIG300 IO-Link Master port access rights configuration.
Tech Tip: The access rights are assigned on an individual port basis! Check them all.
Physical connection Errors in the IO-Link Master
Unlike a simple Ethernet switch, IO-Link ports are not generic. Instead, each port is dedicated to a specific field device. This is no different than the physical connections to rack and slot IO such as the ET 200SP with each wire connecting to a specific I/O pin.
In the fog of 3 AM troubleshooting it is very easy to:
- Swap sensors
- Leave a sensor disconnected
- Fail to tighten an M12 connector leading to intermittent connections
Software Configuration Errors
From TIA Portal, the IO-Link master is handled using a rack and slot configuration. This is shown in Figure 3, where we see the top-level SICK SIG300 representation (left). The “modules” are shown in the device overview (right). For this configuration:
- Port S1 is configured as a digital output
- Port S2 is dedicated to the Banner SD50 display
- Port S3 unused
- Port S4 is dedicated to the SICK W10 distance sensor
- Ports S5 to S8 are unused
Note that each port is mapped to a specific (fixed) memory address within the PLC. This is why the IO-Link field devices connectors cannot be swapped. The PLC would respond with gibberish if, for example, the W10 and the SD50 were swapped.
Figure 3: Configuration of the SICK SIG300 from within Siemens TIA Portal.
Parting Thoughts
Leave a comment if you encounter a problem with your IO-Link system.
- What were the symptoms?
- How did you solve the problem?
- What were the dead ends that consumed time?
Best wishes,
APDahlen
Related Articles by this Author
If you enjoyed this article, you may also find these related articles helpful:
- Guide to Troubleshooting Industrial Control and Automation Equipment
- Understanding the IO-Link IO Device Description (IODD) File
- What is the difference between a Class A and a Class B IO-Link port?
About This Author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians.
Dahlen has returned to his Northern Minnesota home, completing a decades-long journey that began as a search for capacitors. Read his story here.