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Pdsink: USB Power Delivery Sink library for embedded devices

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49 points zdw | 1 comments | 07 Dec 25 04:14 UTC | HN request time: 0.294s | source
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avidiax ◴[12 Dec 25 01:45 UTC] No.46239925[source]▶
I looked at adding USB-PD as a replacement for a 12V barrel-plug power supply in a recent project.

One big issue that came up (and killed the idea) is that if you are not battery powered, then putting a USB-C power input on your device that will only work if you can negotiate 12V+ with adequate current will just cause confusion. In my case, I don't think I could even boot to an error message on 5V.

Phones and the like don't have this issue, since they are still usable (charging slowly) on 5V, but can make use of higher voltages and currents to charge faster.

So I guess my question for the implementer is how booting & negotiating on 5V and then accepting higher voltage is likely to work in practice.

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bri3d ◴[12 Dec 25 03:09 UTC] No.46240454[source]▶
If you absolutely need it, use a separate uC / “trigger” chip for PD negotiation.
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aix1 ◴[12 Dec 25 03:20 UTC] No.46240518[source]▶
I think the GP's point is that this requires a 12V-capable USB power supply.

I have converted pretty much everything I have to USB-C, from toothbrushes to old laptops, and am very happy with the results. My solution is to only own high-quality power supplies with good support for PD. Having done this, the question "Why isn't this thing charging?" doesn't really arise.

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amluto ◴[12 Dec 25 03:29 UTC] No.46240572[source]▶
The common device that this doesn’t work well for is the Raspberry Pi 5. For full power mode it needs an unusual 5V/5A power supply, and that is quite unusual.
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1. Dylan16807 ◴[12 Dec 25 07:53 UTC] No.46241860[source]▶
Specifically it needs a supply that offers 5V/5A as a basic profile outside of PPS (programmable power supply), because the Pi doesn't support PPS negotiations. That is what's so rare, much more than the actual ability to do 5V/5A.