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As per the previous post (which was 5 years ago), I have a device that has three forms of serial communication. One is an RS232, the other is USB A and finally a USB B. So I have three options to connect my PC to this device. The device sends the scanned RFID tags through this serial connection to my PC.

I want to place the reader 60 meters away from my PC. Which type of serial communication should I use?

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    \$\begingroup\$ This was already well answered at the question you linked: Max Serial Cable Length? It should take you no more than a few seconds web search to realize that USB is a short range scheme. A explained at the link, you can try RS232 or convert it to an even longer range differential standard. \$\endgroup\$ Commented Sep 15, 2020 at 22:43
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    \$\begingroup\$ As explained above, if you'd done even the slightest bit of the required self research before posting you would have found out that USB is a short range standard compared to what you learned about RS232 at your own link. Additionally, even the topic matter of this question is off-topic: this is a usage question not an electronic design question. \$\endgroup\$ Commented Sep 15, 2020 at 22:47
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    \$\begingroup\$ USB is limited to 5 meters (about 16 feet) per link. You can extend this by using active repeater cables -- essentially 1-port hubs -- but then you run into the limit on the number of hubs (4, IIRC). So the only viable choice in your list is RS-232. \$\endgroup\$
    – Dave Tweed
    Commented Sep 15, 2020 at 22:49
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    \$\begingroup\$ You can buy a PCBs that will convert RS232 into RS485 and back. RS485 is much better suited to long distance connections like yours. \$\endgroup\$
    – Drew
    Commented Sep 15, 2020 at 22:53
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    \$\begingroup\$ USB A and USB B are only the connector spec. They're both the same USB on the wires. \$\endgroup\$
    – brhans
    Commented Sep 15, 2020 at 22:55

1 Answer 1


The solutions is not that many. But first, is it a option to move the "ALR-F800" closer to the RF reader since it is a Ethernet and PoE device?

Otherwise is the solution only RS232 and at low bit rate. And what bitrate ? It depends mainly on two factors, distance and electrical interference (EMC) from electrical and electronic devices in the proximity to the cable, thus it could be reduced with a god shielded cable.


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