USB Type C connector and cable

[frankb]

The first and most important consideration is whether you are talking about USB 2.0 or USB3.1.
As has been said before in this thread- USB2.0 uses only 5V, GND, D+, D-, CC1 and CC2 (to communicate charge current).
Since USB Type c connectors have so many connectors, it's conventional to use a 0.8mm PCB to fan out the leads, connect the CC resistors and other ICs if relevant, and provide solder points for the wires.
Cautionary tale- making the PCBs for Type-C plugs is tricky (especially with Eagle as it's lightly allergic to milling slots)

Secondly- 3.1 cables are short and often have active components inside.

The standards are quite hard to get to grips with, and it seems the big players get it wrong (from my experience phones with USB Type-C 2.0 will draw more power than the communicated level by the supply.)
Type-C does have some allocation for "other" uses like headphones  (SBU1 and SBU2 I think).
Regarding using it for "custom" pin allocation, perhaps it would be prudent to make a cable from plugs and clearly label things.

Let us know what failures happen from interesting devices being plugged 

[NviGate]

USB Type C is just a connector type, which leads to much confusion. Although it works with USB 2, 3, 3.1 you have to really know your stuff.

I use breakout boards from AliExpress for USB C mostly for power input and output, mainly because when I want to power a project, I always have a charger with a USB C cable handy.

But you need to set the resistor correctly, if memory serves the resistor goes across CC1/2 to VCC. 56K Ohm limits to 500mA, 22K Ohm limits to 1.5A, and 10K Ohm limits to 3A.

Be very sure your project and wires can handle that load.

So, for general power input, it's great. For data transfer, not good unless you stick with D+ D- which are the only guarantee.

For data, I thought about using HDMI Type C, not to be confused with USB C. It has 20 pairs I think. I know some vendors of PCI-E use HDMI cables to transfer.

[ejeffrey]

USB Type C is just a connector type, which leads to much confusion. Although it works with USB 2, 3, 3.1 you have to really know your stuff.

I use breakout boards from AliExpress for USB C mostly for power input and output, mainly because when I want to power a project, I always have a charger with a USB C cable handy.

But you need to set the resistor correctly, if memory serves the resistor goes across CC1/2 to VCC. 56K Ohm limits to 500mA, 22K Ohm limits to 1.5A, and 10K Ohm limits to 3A.

Be very sure your project and wires can handle that load.

So, for general power input, it's great. For data transfer, not good unless you stick with D+ D- which are the only guarantee.

For data, I thought about using HDMI Type C, not to be confused with USB C. It has 20 pairs I think. I know some vendors of PCI-E use HDMI cables to transfer.

All compliant usb type c to c cables are required to support 3 amps and don't have any resistors, the resistors are provided by the device at the other end.  Usb a to c cables are required to have the 56k resistor since all that is guaranteed to be available from a usb type a port is 500 mA.  It still can negotiate higher using usb bc spec up to 1.5 amps on a dedicated charger port (i.e., shorted data pins). Many cables however are not compliant and have the wrong resistor in order to enable faster charging which can lead to failures when used with a usb A port that can't handle the load.  Of course usb a ports are also supposed to have vbus short circuit/overcurrent protection but surprise, not all of them do.