From what I can tell this thread is about powering multiple Pi computers from a single high capacity power supply. Unfortunately, typical multiport USB chargers don't work.As you noted, using PD is not tricky. Connect the PD source to the PD sink and you are done....Yes, no and no.Plug in some USB disks and the Pi 5 needs more than 5v * 3 amp. That means PD. PD is tricky.
- If you are using HDDs or SSDs via USB or via PCIe, a PSU with 5A or greater capacity is strongly recommended.
- It doesn't need to be PD. PD is one way for the Pi and PSU to negotiate 5A. A USB compliant PSU without PD should not supply more than 3A, but a non-USB supply (even if DIY connected to a USB plug) has no such limit. We can configure the Pi to assume that the supply is 5A capable, regardless of whether this is actually the case. Then we have assumed responsibility for keeping the total load below the PSU capacity.
- PD is not tricky. As long as the PSU has a 5V 5A mode, PD should just work and no additional configuration is necessary.
The key issue is that 5V/5A mode is not a required PD mode, it is an optional mode and many/most PD sources do not implement it. Many folks just assume that all PD sources are the same, and that any PD source will "work" (supply the full 5A) with a Pi 5. The reality is that many/most PD sources will only supply 5V/3A, since that is the highest power required 5V mode.
Now, imagine you have 20A of 5V available and want to feed it into multiple Pi computers. At this point USB PD requires suitable USB C wiring along with the circuitry to negotiate with each Pi that it has 5A of 5V available.
While recommendations how to do this are quite welcome, it's possible to override the Pi's need for PD negotiation with boot and firmware flags. Then the trickiness of building your own USB PD power supply can be avoided. This seems the practical way to power multiple Pi computers to me.
Statistics: Posted by ejolson — Mon Jul 22, 2024 2:58 pm