On dev boards, the 5V supply of the USB connector is generally routed out to a pin on the board so that one can power other devices off the board. Often you can also use such a pin to power the board from an external source and to handle this case the VBUS of the USB connector is protected by a diode so that the external supply doesn’t damage your laptop/PC’s USB port if it’s connected at the same time.
Usually, the hookup guides for SparkFun dev boards have a small section about powering them via one of the board’s pins rather than USB. The [hookup guide for the Pro Micro - ESP32-C3 has no such section so, I thought I better check the [schematic. And I was really surprised to find that V_USB of the USB connector seems to be exposed directly on pin 1 of the board’s J7 header with no diode in between.
I find this so surprising that I wonder if I’m missing something. SparkFun is very experienced at board design and it knows that the target audience for its products often has little experience in the electronics field. Damaging ones laptop or PC is about the worst outcome for a hobbyist (vs, at worst, seeing the magic smoke escape from e.g. a $20 dev board).
So, I’m wondering if has something changed in the world, e.g. that USB-C power sources are required to be smart enough to detect external power when they were otherwise expecting to be the power source and that as such the protective diode is no longer crucial? My impression is that this is not the case.
I remember several years ago that no-name so-called blue-pill STM32 boards on AliExpress caused consternation in the community when it was found some of them were omitting the usual diode that protects the VBUS of the USB connector. SparkFun is not a no-name AliExpress vendor, it’s a reputable hobbyist-oriented company with years of experience in this area so is there some explanation here that I’m missing?
Maybe it’s as simple as the schematic being out of sync with the actual board?
For reference, here’s the kind of layout I’d expect to see. Here VBUS is connected to the on-board regulator and between it and the +5V pin exposed by the dev board is the diode D1.
](https://cdn.sparkfun.com/assets/5/a/6/f/e/SparkFun_ESP32_C3_Pro_Micro_Schematic1.pdf)](Hardware Overview - SparkFun Pro Micro ESP32-C3 Hookup Guide)