Given that this is the only practical application you have to wonder why we ever had the one way plugs in the first place.
Firstly, reversible plugs are harder to make structurally resilient, they only become feasible cost-wise as stronger materials become cheaper and manufacturing grows more efficient.
Secondly, reversible plugs are a lot more complex. Compare the 4(ish) pins of USB-A to the 24 pins on USB-C. Not all of them are strictly necessary for parity with USB-A, but you could cut that number in half quite easily if the plug were not reversible! Sure, this complexity impacts manufacturing, but, less obviously, it also pushes that increased complexity onto the USB controller hardware/firmware.
Neither of these issues were necessarily dealbreakers, but... for a long time they certainly did conspire to make reversible plugs into a pipedream. I have to imagine that were always bigger problems to solve and fewer resources to work with! We're just now seeing reversible plugs really take off because we've finally crossed that magic threshold where it makes sense to try surmounting those barriers.
Meanwhile we were connecting printers, scanners, and other peripherals using a 25-pin parallel (or sometimes SCSI) plug. Granted, the DB-25 was already pretty old at that point, but I have to imagine a 24-pin reversible USB plug would have been close to that size if it had been developed in the 90s.
The physical design of FireWire was one of its many advantages, in that you could instantly tell, visually and by touch, which side was up by the beveled corners on one side of the plug. I’m guessing the answer here was again cost, that manufacturing an interconnect with two 90-degree angles and four 45-degree angles was more expensive than one with four 90-degree angles, but I’ve never seen any confirmation of this.
The sole reason as stated by Ajay Bhatt, the project lead at Intel, was cost. They wanted to encourage mass adoption of USB and every cent saved helped in that initiative.
The compromise for UX was to make the connector rectangular rather than circular, so that there was a 50% chance of getting it correctly orientated on first try.
I never ended up getting a camera or anything else that supported FW, but USB always seemed to work well enough for my (relatively light) use case.
Fun fact: USB 2 Mini/Micro connectors actually have 5 pins (hence my original 4-ish statement). The 5th pin doesn't actually go over the wire, it's just used as a signalling pin to the controller that tells it if the plugged in device is compatible with USB OTG.
Not precisely. The type C connector has four distinct USBSS pairs; the type A connector only has two. This allows the type C connector to be used to carry DisplayPort or other high-speed data alongside USB.
[0] https://upload.wikimedia.org/wikipedia/commons/thumb/0/07/US...
I'm fairly certain they are using double the number of USBSS because they're available due to the mirroring. It was the easiest way. Unlike the control channel or side band, you can actually benefit from using all the pairs for data transmission since they're already there.
Lots of cool applications using that technique.
This is misleading.
If you want to only cover the USB-A spec with USB-C, you need only 8 pins.
I have a cheap USB C on my desk that got 8pins because it do only USB and charge.
USB-C can pass HDMI signal on the other pins, which your USB-A can't do.
> Not all of them are strictly necessary for parity with USB-A, but you could cut that number in half quite easily if the plug were not reversible
Is 4 not half of 8?
Also: USB-B micro connectors might have 5 pins, but the cable itself has 4 wires. The OTG pin is grounded in the connector. This is actually why I said "4(ish)" in my original post.
Thats why USB-C have more or less the same speeds than HDMI, while the HDMI have 22 connectors.
Compare what is comparable, you can't use your USB-A to display 4K-60Hz video, but you can with your USB-C, or HDMI.
I used them for plugging into public power supplies, but they were never sold to consumers labeled for that purpose.
A one-way plug would be fine if the profile were sharply asymmetrical, to the point where one could find the right orientation by touch alone. Maybe something like an even more pronounced trapezoid than hdmi.