Post #3289053
2026-06-07 17:28 UTC
Replies (2)
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@gsuberland@chaos.social 2026-06-07 17:32
@matildalove@wetdry.world @valpackett@social.treehouse.systems many cheap sources just give you 5V with no particular current limit - just whatever the supply can handle until the voltage sags out of spec or something overheats. they don't bother looking for the 5.1kΩ resistors. this generally just works because the supply can handle at least 5V 1.5A, so it doesn't matter if the resistors are present or not, and if the device tries to actively handshake for higher voltage/current it detects that the source doesn't support it.
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@niconiconi@mk.absturztau.be 2026-06-07 18:56
@gsuberland@chaos.social @matildalove@wetdry.world @valpackett@social.treehouse.systems I don't think it's correct. The CC1/CC2 resistors are not just used in the Power Delivery extension, but are also a mandatory part of the USB-C base spec. The use is required. If CC1/CC2 are open circuits without resistors, the USB-C source is required to treat the port as "not connected", as a result no power is applied. See "4.5.1.2.1. Detecting a Valid Source-to-Sink Connection", "Table 4-10 Source Perspective" and "Table 4-11 Source (Host) and Sink (Device) Behaviors by State" of Universal Serial Bus Type-C Cable and Connector Specification (rev 2.0, 2019). Native USB-C devices are expected to include resistors to even be allowed to use USB-C, otherwise it's a completely fair game to get no power at all from a strict USB-C source (USB-A to USB-C cables have resistors built-in). The non-compliant devices creep in exactly because most USB-C sources are not that strict.