It cannot be a host port
Build a 5 V supply, fit this board as the socket a phone plugs into, and nothing charges. No power, no error, no clue. A board that takes power and a board that gives it need opposite resistors, and this one is soldered for taking.
Two directions, opposite resistors
A USB-C connection has a side that supplies power and a side that takes it. They are told apart by what each puts on the CC line:
- The side taking power pulls CC down to ground through 5.1 kΩ.
- The side giving power pulls CC up towards 5 V — 56 kΩ, 22 kΩ or 10 kΩ, depending on how much it is offering.
Both sides are resistors on the same wire, and the resulting voltage is how each learns what the other is.
This board is permanently the taking side
Its two 5.1 kΩ resistors go to ground and are soldered there. Plug the socket into a charger and everything works, because that is the arrangement the board is built for.
Fit the same board as the outlet on a supply you built, so a phone can plug into it, and you have two pull-downs facing each other. Neither end sees the voltage move. Neither end decides anything has happened. VBUS stays off, and — this is the part that costs people an evening — nothing reports an error, because from each end's point of view nothing has been plugged in at all.
The symptom to recognise
Everything is soldered correctly, your 5 V supply is definitely working, the phone is definitely working, and the phone behaves as though the cable is not plugged in. If that is what you have, stop checking your soldering. The board is doing exactly what its resistors say and the resistors are the wrong ones for the job.
What to use instead
A board meant to be a source, with pull-ups rather than pull-downs. The value sets what it advertises: 56 kΩ for 500 mA, 22 kΩ for 1.5 A, 10 kΩ for 3 A — and whatever you advertise you have to actually be able to supply.
You could convert one of these by removing both 5.1 kΩ parts and fitting pull-ups to 5 V. It is a fiddly job on 0603 pads, and it leaves you with a board that can no longer do the thing you bought twelve of them for.
Why the board is built this way round
Because taking power is the case that comes up. Almost everything a hobbyist wants a USB-C socket for is getting 5 V out of a modern charger — the wall warts, the power banks and the laptop ports that no longer have a USB-A socket on them. Being a source is a rarer job with harder requirements, since you then have to supply the current you claimed.
When it does not work
Working as designed, unfortunately. Your phone is looking for a pull-up on CC to tell it a source is present; this board has a pull-down. Two pull-downs facing each other means neither end ever sees anything change, so no power flows and nothing reports a fault. You need a board with 56 kΩ, 22 kΩ or 10 kΩ pulling CC up to 5 V instead.
No, for the same reason. The end that plugs into the host is fine — it presents a pull-down, and the host obliges. The end your device plugs into also presents a pull-down, and your device is waiting for a pull-up. The power half will never start. Buy an extension cable; the parts in one are not the parts in two of these.
Physically yes — they are 0603 parts on exposed pads. Practically it is a poor trade: you would be removing two parts, fitting two others to 5 V rather than ground, and finishing with a board that can no longer do the thing it is good at. A purpose-made source board costs less than the hour.
Do not go looking for a way. Two sources both pulling CC up will not switch on into each other, which is the specification protecting you, but the reason that protection exists is that back-feeding a source's output is a genuinely bad idea. Nothing in this book asks you to.
What D+ and D− can carry, why the socket has four contacts for two pads, and what reversibility costs.
USB 2.0 data, and what is missing →Edit this page — content/books/usb-c-breakout/it-cannot-be-a-host-port.mdx
Questions about this product
See what other owners have asked, and read their solutions.
USB-C Breakout Board, 12-Pack with 5.1 kΩ CC Resistors
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