3 ms·

> but can my laptop's USB-C port support PD in both directions (charging and powering a peripheral)?. Two of the USB-C ports of my Dell XPS 13 9380 provide 5A/

> but can my laptop's USB-C port support PD in both directions (charging and powering a peripheral)?. Two of the USB-C ports of my Dell XPS 13 9380 provide 5A/3A over PD, and the third one provides 5A/1.5A. All of them can negotiate both sink and source PD contracts. If your laptop can be charged via USB-C port and you can attach peripherals to the same port, it's almost certain that it can negotiate a source PD contract as well. That doesn't automatically mean you'll get more than 5V though, so such PD port may still be useless for powering a disk drive enclosure without additional voltage regulation.

Kirby64 4y ago
I'm assuming you mean 5V/3A and 5V/1.5A. If so, that is explicitly NOT PD. USB-C supports 3A and 1.5A purely by setting resistor values on the CC pins, and does not require the BMC PD negotiation protocol. Many PD controllers support this for 'sourcing' (5V/1.5A or 5V/3A) natively, since it's a common use case for laptops.
- seba_dos1 4y ago
  No, this is 5V/3A and 5V/1.5A as communicated via PD 3.0. In this case you can achieve the same result without PD (well, almost - you still need it for role swap), but that's not what I was talking about.
  - Kirby64 4y ago
    What scenario would your laptop be providing power (being the source), while simultaneously being the receiver of data (data sink)? Not sure I see the use case for that, regardless of whether you can achieve 5V/3A over PD.
    - seba_dos1 4y ago
      You need PD for power role swap, for example when (un)plugging a power supply to already connected USB-C hub. You also need PD for alt-mode negotiation. You can negotiate a 5V/3A contract to, let's say, power a DisplayPort/HDMI dongle - that won't work by simply signaling 1.5A or 3A with a resistor.
      - Kirby64 4y ago
        Understood you need PD for alt modes, that's a given. I never thought about the scenario where you have a powered USB hub and you switch from powering it via a brick to powering it via your laptop... interesting, and actually very reasonable scenario. I guess given you have PD already built-in, it's not too hard to integrate that functionality either.

Kirby64 4y ago

I'm assuming you mean 5V/3A and 5V/1.5A. If so, that is explicitly NOT PD. USB-C supports 3A and 1.5A purely by setting resistor values on the CC pins, and does not require the BMC PD negotiation protocol. Many PD controllers support this for 'sourcing' (5V/1.5A or 5V/3A) natively, since it's a common use case for laptops.

seba_dos1 4y ago
No, this is 5V/3A and 5V/1.5A as communicated via PD 3.0. In this case you can achieve the same result without PD (well, almost - you still need it for role swap), but that's not what I was talking about.
- Kirby64 4y ago
  What scenario would your laptop be providing power (being the source), while simultaneously being the receiver of data (data sink)? Not sure I see the use case for that, regardless of whether you can achieve 5V/3A over PD.
  - seba_dos1 4y ago
    You need PD for power role swap, for example when (un)plugging a power supply to already connected USB-C hub. You also need PD for alt-mode negotiation. You can negotiate a 5V/3A contract to, let's say, power a DisplayPort/HDMI dongle - that won't work by simply signaling 1.5A or 3A with a resistor.
    - Kirby64 4y ago
      Understood you need PD for alt modes, that's a given. I never thought about the scenario where you have a powered USB hub and you switch from powering it via a brick to powering it via your laptop... interesting, and actually very reasonable scenario. I guess given you have PD already built-in, it's not too hard to integrate that functionality either.