VM8090 Data Packet Length

Hi. We have around 40 of the VM8090 boards in use with bespoke software. The software has been in use for over 10 years and the boards work really well but I’m looking for clarification on one thing please… the software is based around querying the boards and executing logic based on the 8 bytes received.
Over the past few months, several of the boards occasionally seem to be returning only 4 bytes which is reported by the software - it throws an error if less than 8 bytes are received from the com port.
Could you confirm is this is purely due to data corruption, such as a faulty usb cable or external interference? I guess the other possibility is a faulty board/component?
We recently installed a usb extender (over cat5) as a test due to the length of some usb cables but we still have this issue infrequently.
The worse case we have, has this issue no more than 6 times per day, sometimes one at a time and other times, several times in quick succession. It’s not causing us any major issues but I’d really like to know the reason.
Any help appreciated, thanks.


In our opinion, this is due to the USB cable being too long and causing data loss (reflections, interference). It is also possible that the USB extender cannot cope with data (incompatible). We suggest using USB cables of type 2.0 and cable lengths less than or equal to 1m and check whether this continues to work without any problem. that way, you will know for sure if it is due to the length or extender.

Also make sure that no voltage or PWM cables (example of Dimmers or switch mode power supplies) run along the USB cables or CAT5 data cables. Because voltage cables or PWM can interfere on USB cable and CAT5 cable, an so corrupting the data. Better in this case is to use a Shielded Folded Twisted PAIR cable SFTP or an SFTP CAT6. and connect the shield as well as to RJ45 connectors and Shielded extender. Or separate the Voltage and PWM cables from USB or CAT5 cable.

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