is fairly broad (what isn't serial nowadays...), and most of the current tags are really referring to UARTs (), but a (scant) few questions are using it more generally.

Cleanup from that rename would be pretty easy, but probably more annoying would be the maintenance burden it places on the site, as naive most Arduino users will just tag and probably not know what a UART is, so it will need to be fixed again, and again, and again...

Or we could leave it as is...but that hurts me inside.


5 Answers 5


I think the problem is more complicated than that. For example, you can have:

  • Asynchronous Serial
    • logic level
    • RS232
    • RS485
      • CAN bus
  • Synchronous Serial
    • SPI
    • I2C
  • High-speed Serial
    • USB
    • Digital Video

And this is not a complete list.

I don't like the idea of using UART as a tag for all traditional asynchronous serial topics. To extend your perl analogy, it would be like tagging all perl questions [perl.exe] instead of [perl]. Most people, when they say they are using a serial connection, are using a logic level (0-3.3/5V) asynchronous serial protocol: 8 data bits, no parity, and one stop bit (8N1). I think a better retagging target would be [asynchronous-serial], but that's still a bit amorphous and vague.

The other problem is that manufacturers start adding additional letters to the "UART", twisting the meaning of the tag. I've seen things like USARTs and EUSARTs, which have replaced the simple traditional UART. Manufacturers like these extended functionality ports because they support so many protocols - extending way beyond the original connotation of UART.

  • \$\begingroup\$ I've only ever seen the additional letters on the actual hardware, so there how you configure and use it will determine how you would tag a question about it. What would fall under [uart] that wouldn't fall under [async-serial]? \$\endgroup\$
    – Nick T
    Feb 13, 2011 at 18:20
  • \$\begingroup\$ excellent comment. I added "logic level" under async serial, because RS232 specifies certain voltages. \$\endgroup\$
    – markrages
    Feb 14, 2011 at 1:56
  • \$\begingroup\$ @nick here's an example of async decoding that doesn't use a uart: vivara.net/blog/?p=24 \$\endgroup\$
    – markrages
    Feb 14, 2011 at 1:57
  • \$\begingroup\$ @mark That's backwards \$\endgroup\$
    – Nick T
    Feb 14, 2011 at 2:24
  • \$\begingroup\$ hm, I've made "ATs" in firmware many times. No "U", no "R". And sometimes I've made "ARs". No UART hardware was involved. Does that count? \$\endgroup\$
    – markrages
    Feb 14, 2011 at 2:42
  • \$\begingroup\$ I would think that UART limits itself to the configuration of a hardware transceiver. Discussions about topology, hard-wired hardware (not Universal), and protocol would be a stretch under the [uart] tag. It would be nice if we could use [rs232], but as @mark mentioned, that excludes many common use cases because of different voltage requirements. \$\endgroup\$
    – W5VO
    Feb 14, 2011 at 12:55
  • 1
    \$\begingroup\$ UART doesn't necessarily imply any particular hardware transceiver. TTL, various RS's (232, 422, 423, 485, 530), MIL-STD-188, etc could all be driven from a UART. Some of these are interoperable and some are not, and some are under certain conditions only. You could even make up your own physical layer, drive it from a micro, and it'd be "UART" and "serial". \$\endgroup\$
    – John Lopez
    Feb 15, 2011 at 0:02
  • \$\begingroup\$ @John I think we're confusing terminology here. When I say "transceiver", I'm referring to the hardware/software that interprets the logical values present on the physical medium. A Driver+Receiver, or a level shifter would be what I call the actual hardware driving a voltage protocol like RS232. Of course, I also recall "transceiver" being used to describe a chip that does the voltage encoding of a protocol, so I might be confusing the situation. \$\endgroup\$
    – W5VO
    Feb 15, 2011 at 1:43

Well, you can also set up a synonym, but I have to admit -- I hear serial a lot more. Is the distinction that important? Will people want to discuss but not ?

In other words, is there a meaningful difference between the tags at all?

  • \$\begingroup\$ Within the world of electronics, uart is fairly specific but still common. Yes, an unqualified "serial" generally implies that someone is talking about a UART, but if we're sorting and classifying things with tags, I'd think being proper should win out over colloquial usage that is reliant on context. \$\endgroup\$
    – Nick T
    Feb 7, 2011 at 3:49
  • 5
    \$\begingroup\$ Not sure what you know of the topic, but a rough translation of your question into web-dev speak might give something like: Will people want to discuss [perl (or some language people write scripts in)] but not [scripts]? \$\endgroup\$
    – Nick T
    Feb 7, 2011 at 3:56

The distinction can be important. All UARTs are serial, but not all serial interfaces are UARTs.

For example, this ER question should not be tagged UART because a UART interface (5 to 9 data bits, 1 to 2 start/stop bits, etc) will not work for the application.

  • \$\begingroup\$ Yes, as I mentioned, some questions will need to be fixed after such a change. Having a mod do it, however, would remove the need for I or someone else to bump ~40 questions to the front. \$\endgroup\$
    – Nick T
    Feb 12, 2011 at 23:18
  • \$\begingroup\$ Well, this example should probably be tagged spi or ssp. \$\endgroup\$
    – W5VO
    Feb 13, 2011 at 17:16
  • \$\begingroup\$ SPI? No, just because it's synchronous doesn't mean it's SPI. SSP? Maybe, but that's hardly a common acronym - you lose clarity to save 2 chars in the tag. \$\endgroup\$
    – John Lopez
    Feb 14, 2011 at 23:51

I like the tag . It is about as useful as the tags or , which, while valid tags, need to be used sparingly, only when better, more specific tags are not possible. Unfortunately this hasn't happened: 180 questions have been tagged (only 26 have been tagged , which, for a site that isn't supposed to be about software other than DSP, I still think is high).

There are currently 40 questions tagged -- a large chunk considering the relatively small question base. Many of them can be more appropriately tagged something else, or additionally, but not all (or even most) to . Change the ones that don't fit. If someone doesn't like your edit, they can edit in turn.

I think those of us that edit often will go through a period where users will disagree with many our choices and make changes on their own. It is important that we don't take this personally, instead embracing the exchange as a debate between peers. Reminds me of Wikipedia... if someone is a regular from that community, please provide tips!


For me as a beginner serial is very common but uart is not.


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