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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?

JoeyB
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    This was already well answered at the question you linked: [Max Serial Cable Length?](https://electronics.stackexchange.com/questions/187633/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. – Chris Stratton Sep 15 '20 at 22:43
  • @ChrisStratton that is a similar post in my question that is clearly shown. In addition, this question is different because I trying to find out which is better, USB A, USB B or RS232. This clearly differentiates my question from the previous post. Not sure how much more clear I can be. – JoeyB Sep 15 '20 at 22:45
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    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. – Chris Stratton Sep 15 '20 at 22:47
  • @ChrisStratton then why was not the other question closed down? – JoeyB Sep 15 '20 at 22:48
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    Doing a google search for "USB cable length", I find many sites stating that USB is llimited to 5 metres/16 ft. – Peter Bennett Sep 15 '20 at 22:48
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    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. – Dave Tweed Sep 15 '20 at 22:49
  • @DaveTweed Thank you – JoeyB Sep 15 '20 at 22:49
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    You can buy a PCBs that will convert RS232 into RS485 and back. RS485 is much better suited to long distance connections like yours. – Drew Sep 15 '20 at 22:53
  • @ChrisStratton please address the other post. Clearly this is creating a lot of inconsistencies on this platform. Makes it seems that there are no rules. – JoeyB Sep 15 '20 at 22:54
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    USB A and USB B are only the connector spec. They're both the same USB on the wires. – brhans Sep 15 '20 at 22:55
  • @Drew 1220 meters is definitely enough. Thank you. – JoeyB Sep 15 '20 at 22:57
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    Is it not possible to do SSH via virtual serial port or Raspberry Pi to help you interface with your device from a distance? –  Sep 15 '20 at 23:38
  • more than 20 years ago, I was at TI Germany. The guys there told me, they just archived more than 50 meters RS232 with their best chip in laboratory conditions - and I do not remember the speed. I would consider 60m of RS232 not something practical. You want a differential bus, like RS422/485, CAN, (M-)LVDS, Ethernet. Each of them will do 60m. Or search for a glasfiber converter. They are common for EMV test chambers and also should do 60m with ease – schnedan Sep 16 '20 at 06:23

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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.

Mats Karlsson
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