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Troubleshooting inability to read tags

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Overview 

This article will cover various techniques to help you overcome the challenge of not being able to read tags in your application when tags are clearly in the antenna's field of view. 

 

Use the Latest Software Releases

Please ensure you're working with our latest releases of firmware, software (e.g. ItemTest), and development libraries.  Bug fixes and enhancements are only applied to our latest releases.

Upgrade the Reader Firmware

Please start by upgrading to the latest firmware version on all readers and gateways.  You can get this firmware from the Impinj Partner you purchased your hardware from.  If you are an Impinj Partner, please login to the support portal and download the latest version.

Upgrade the Software

Please upgrade to the latest versions of ItemTest, Speedway Connect, and/or ItemSense.

Upgrade the Development Libraries

Please upgrade to the latest versions of the SDK, LTK, or ETK libraries.

Capture Reader Configurations

The reader/gateway configurations play a critical role in determining whether a setting is causing the reader to miss tags. Additionally, you will need to provide Impinj Support (should they need to get involved) this information.  Please follow the instructions at https://support.impinj.com/hc/en-us/articles/202756208-How-do-I-send-you-my-reader-config-and-settings- for acquiring the reader/gateway configuration and settings.

Compare Configurations

In situations where the tags are being read on one reader but not by another, we suggest comparing the configurations of the two readers to find differences that could be causing this issue.

Application Changes

If none of the above items work, try making application-based changes to help figure out what is going on.

Test with a different application

Try another application if your application is not reading tags.  Our ItemTest software (https://support.impinj.com/hc/en-us/articles/208589707-Impinj-ItemTest-Software) is a great tool for doing just that.  Alternatively, you can try one of our Octane SDK examples or Speedway Connect.

Test with different application settings

Try enabling antennas, disabling start triggers, removing filters, changing Reader modes, changing reader search mode and session, and/or testing different Transmit Power and Receive Sensitivities.

Antennas

Disabled antennas will not read any tags  Ensure the antennas are enabled in your application.

GPI Start Triggers

If GPI start triggers are set to something other than Immediate, the reader may not be running. Check the status lights on the front of the reader or the WebUI to see if the reader is running or not.

Filters

Filters could prevent tags from being reported. There are two types of filters that should be disabled: Gen2 and software filters.

Disable Gen2 Filters in ItemTest

Under Reader Settings -> Configure, you will see Optional Settings for setting a filter at a specific place in tag memory.  If you aren’t getting any tags reported, make sure this filter is empty

Disable Gen2 and Software Filters in Speedway Connect

Disable filters in Speedway Connect by

       - Disabling “Filtering: Software” and
       - Disabling “Filtering Gen2 (HW Select)”
NOTE: we have a separate Speedway Connect Troubleshooting Guide located here: https://support.impinj.com/hc/en-us/articles/115001233464 for additional troubleshooting information.

Reader Modes

A more sensitive reader mode such as Dense Reader M8 may help read those hard-to-reach tags. 

Reader Search Mode and Session

If using Single Target Session 2 or 3 or Single Target w/ Suppression, the persistence may be causing the tag to not be reported. If using the Single Target Reset search mode, tags will not be reported unless already energized. Change the configuration to Dual Target or Single Target Session 0 and try to read tags again.

Reader Transmit Power and Receive Sensitivity 

Reader transmit power may be too low and receive sensitivity may be too high.  To help determine the right settings, perform a Margin Test.

Change Sequence Stop Trigger of Tag Op Sequence

If you set Target Tag Data to NULL passed it to ImpinjReader.AddOpSequence(TagOpSequence sequence) you will end up only reading one tag.  The default behavior for a TagOpSequence is to have an execution count of 1. Thus only one operation happens. You will need to set the SequenceStopTrigger to the "None" enum value to overcome this.

Perform a Margin Test

A margin test will perform a power sweep and tell you what minimum amount of transmit power is needed in order to read tags.  Make sure to run multiple tests.  Here is an article with more details for how to conduct the Margin Test: https://support.impinj.com/hc/en-us/articles/202756388-Performing-a-Margin-Test-using-Impinj-ItemTest-software.

Verify Application is Connected to the Reader

You will no longer get tag reads if your application is no longer connected to the Impinj Reader.  We recommend using Keep Alives and LinkMonitorMode features when writing your own software applications with our libraries.  These features will help in determining whether the connection is still active and when it is not, that is a sign your application needs to reconnect.

Disable the on-reader application

If you have an on-reader application running, disable or remove it and check to see if tags can be read with a different application like ItemTest.

Hardware Changes

If software is not the problem, here are some hardware related changes you can make.

Consider tag usage

Occasionally, tags can get damaged and cease to function.  This damage may or may not always be visible to the naked eye.  Check the tag and replace with a known-good one to eliminate this potential problem.

Tag sensitivity continues to increase with new generations of Monza products.  Additionally, the size and mounting location can affect how well a tag is able to be read.  Having a mixed population of tags (both chip and inlay size) can make it appear that some tags are not able to be read.  When possible, select tags with the same Monza chip family (e.g. all Monza 6) as well as same inlay size.  If your use case allows, control tag placement and ensure tags are not being blocked by other objects or stacked directly on top of each other.

Ensure the tag you're using is compatible with the item that you're trying to track.  For example, special metal-mount tags are essential when applying a tag directly to a metal object.

Replace the cables and peripherals

There could have been a loose cable, bad antenna or hub, or under-performing power adapter or switch.

Change the power source

Please change the power source.  The hardware may act differently when connected via 802.3af POE vs wall power (brick).  Make sure to use the Impinj-supplied power adapter.  Otherwise, regulatory compliance is customer’s responsibility.

Change to a different POE Switch port and/or disable POE on the switch.

Replace the reader/gateway with another reader/gateway

Changing out the reader/gateway will help determine whether we have a reader/gateway issue or what the reader/gateway is connected too is the issue.

Environmental/System Considerations

Analyze the environment where tags need to be read.  Take pictures or video of the space and use case.  Identify any sources of metal in the area.  Metal causes reflections which result in unpredictable “hot spots” (areas with enhanced readability) and “nulls” (areas where no tags can be read).  Check for other sources of interference in the area (e.g. fluorescent lighting).  The best method for determining this is to conduct a RF survey with a spectrum analyzer.

When multiple readers are covering the same area, ensure the readers are running the same reader modes and are configured to reduce interference.  To manage tag populations that need to respond to multiple readers, set adjacent readers to different reader sessions.  In the ETSI region, assign complementary RF channels to adjacent readers.

As part of the RF site survey, identify other systems that use wireless spectrum in the same band as the readers and gateways are operating in.  For example, here are example systems we've encountered that share similar operating frequencies:

  • RFID handhelds
  • Wireless phone systems
  • Wireless overhead crane/lift systems

Capture Reader/Gateway Logs

It is possible there is an error in the log files that explains why something is not working.  Additionally, you will need to provide Impinj support (should they need to get involved) this information.  Please follow the instructions at: https://support.impinj.com/hc/en-us/articles/202756238-How-do-I-capture-logging-events-from-my-reader- to collect the reader/gateway logs.

 

Increase the logging level

Additional information provided by logs may help identify problems the reader may be experiencing.

How to do it

1) SSH to the Reader with a tool like putty
2) Login as user root
3) Issue RShell commands:
    • config logging rfid debug
    • config logging management debug
    • config logging system debug

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Impinj (NASDAQ: PI) wirelessly connects billions of everyday items such as apparel, medical supplies, and automobile parts to consumer and business applications such as inventory management, patient safety, and asset tracking. The Impinj platform uses RAIN RFID, delivering information about items to the digital world and enabling the Internet of Things.