Cord Failure – Case 1
Things most prone to fail are those that are physically moved, twisted, bumped, connected, power cycled, and so on. In my particular world that means cables and ports. This failure example is a 15ft USB 3.0 Tether Tools cable. It’s basically a generic USB A to USB Micro-B cable in bright orange with copper internals that are just as prone to the physical constraints of the environmental abuse as any other cable1.
In this example we caught the connection would interface but immediately disconnect. We had been operating outside in ~30-40f weather and thin metal cables are prone to breaking. After a day of successful shooting with the cable, we experienced a random failure. Which after a quick inspection, revealed to be the issue of a missing/broken pin.
Below we see the pin-out diagram of a USB 3.0 Micro-B connector. For the sake of brevity we don’t need to understand the pins or their role except for the fact that the legacy/important connection is the USB 2.0 Connector. Cameras will operate—albeit at a slower speed—without the additional USB 3.0 Portion of the connector.
Back home we’ve taken a cursory glance at the connector under the microscope. Example A is a functional connector. And yet even a regular cable that meets specification can have a vital USB 2.0 pin that sits too short in the connector and cause disconnects with the slightest of movement against the port.
In Example B it’s quite clear we no longer have Pin 1. A USB 3.0 Spec Micro-B connector is the USB 2.0 connector besides the additional USB 3.0 Pins—See original pinout diagram. We can safely2 damage the USB 3.0 pins and still use the cable albeit at the slower transfer rate but if we damage the legacy USB 2.0 pins in any way, we are out of luck. Further, we can use legacy USB 2.0 Micro-B cables with general success, again at a relegated performance.
This cable was adequately clamped with various tether locking solutions yet none of them truly secure the connector and the port. Tether Tools do not include operating temperatures in their specs sheet so it took a little searching to find a generic answer of ~0c-50c. Given these variables and the nature of a well used cable, we find this failure surprising and unfortunate, but not shocking.
USB C Pinout
Whilst we’re looking at the fragility 5 pins afford us, it would be interesting to take a look at the pins available on a USB-C port. A reversible, 24 pin receptacle rated for a variety of different applications that far exceed the capabilities of their older USB specifications.
This adds a significant layer of confusion and misunderstanding with respects to the capabilities of the host, the sink and more importantly the cable itself. All these parameters are now negotiated as part of the process of plugging the device in and what the capabilities of the cable are during those negotiations – a topic we’ll explore further.
- If you’d like a less expensive option that provides the same result, use a solid repeater and shorter USB 3.0 Micro Cable as the short cable will be the thing to replace. Generic hard drive bundled cables work great. ↩
- Safely does not mean successfully. Operative hardware may cease. ↩
- USB-C Testing: https://plus.google.com/collection/s0Inv
- USB-C Cable & Connector Spec: http://www.usb.org/developers/usbtypec/
- qualMeter: http://www.qoopow.com/
- Micro-B USB 2.0 Spec: https://www.mouser.com/pdfdocs/HiroseZXSeriesConnectors.PDF