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I have a PD capable charger. One interesting thing that I noticed is that if I directly plug a type-C to USB-A cable into it, I can get 5V.

However, if I use a PD compatible C-to-C cable, I can't get 5V from it (my device has a female C port with no PD negotiation chips, it doesn't charge).

Measuring various VCC and GND after attaching a breakout board to the connected type-c cable all yields 0V. I tried another c-to-c cable, the same thing happens.

Pluggin the breakout board directly into the charger, there's no 5V as well.

What could be the reason behind this?

Marcus Müller
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Larry Lee
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  • the 5V on the classical USB VBUS line should practically always be present, so I'm guessing your breakout board is to blame. – Marcus Müller Jul 24 '21 at 14:43
  • You won't get 5V from a USB-C port without pulldown resistors on the CC pins. Does your breakout board have them? – Finbarr Jul 24 '21 at 14:49
  • @MarcusMüller my board is good, I think it's more of sth @ Finbarr is saying. – Larry Lee Jul 24 '21 at 15:02
  • @Finbarr, it's just a bare board, no resistors or anything. I'm trying to add a pull downresistor. I had this little type-c to usb 2 adapter, I could get a 5v from the VBUS and the GND after plugging it into the charger. – Larry Lee Jul 24 '21 at 15:04
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    The adapter probably had resistors built into it to activate Vbus. – Finbarr Jul 24 '21 at 15:17
  • @Finbarr exactly! – Marcus Müller Jul 24 '21 at 15:25
  • Yep, the correct Pd resistor should be a 5.1k resistor, got my 5V all right. – Larry Lee Jul 24 '21 at 15:35
  • @MarcusMüller, your comment on VBUS ought to be always present should be taken into consideration by those guys managing the PD protocol. It's a helpful feature after all. – Larry Lee Jul 24 '21 at 15:41
  • @Finbarr Interestingly, my phone support's PD as well. Whenever I connect it to my computer the option of (Charge the connected device) appears, but after connecting the breakout board with the CC pulled down, nothing shows up, any idea what could be the reason? – Larry Lee Jul 24 '21 at 15:51

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