Did it really take them so long to think about a symmetric port?


closed as primarily opinion-based by Andy aka, Michel Keijzers, Dave Tweed Nov 9 '18 at 11:32

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Closed? Really? I actually thought it was quite a good question as many newer engineers forget how far we have come since 1996 when USB was first introduced. It was truly state of the art back then. \$\endgroup\$ – Jon Nov 9 '18 at 11:34
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    \$\begingroup\$ @Jon: It might be an interesting discussion, but unless somebody has some verifiable facts, it would be pure speculation, which is not what this site is about. Take it to chat. I recommend Googling "USB history" to get some perspective about what was driving the decisions in the 1994-98 timeframe when it was being developed. Symmetric connectors were simply "not a thing" at that time. \$\endgroup\$ – Dave Tweed Nov 9 '18 at 11:42

Although @jsotola has a point (never underestimate the stupidity of users - they’re so creative!), the answer is more likely to be “complexity”.

USB was a proposed solution to a problem, and to succeed needed to be adopted as quickly and broadly as possible. To facilitate this, it above all needed to be cheap. This means that it needed simple circuitry, and as few proprietary chips as possible.

There are two sides to “symmetric” (pardon the pun):

  • You can insert the connector either way around;
  • Either side can provide or demand power.

The first adds complexity in wiring; the second adds complexity in power design. Both would have added to the cost, reducing the chances of widespread acceptance.

Now that USB has gained de facto ubiquity (even Apple have gone USB-C!) you can make these sort of user-experience modifications - and have no doubt whatsoever that they’re very complex and difficult! Getting it right has eluded many suppliers for a long time. Luckily, a number of chip manufacturers have solutions to help, so they’re not as expensive as they would have been at the beginning.


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