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GroundStudio / GroundStudio_Marble_Pico

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Powering via USB and VBUS concurrently #3

Closed CatalinMustata closed 7 months ago

CatalinMustata commented 7 months ago

Hey guys! I'm planning to use the board as a brains for a guitar effects looper and most of the time it will be powered through it's own power supply through the VBUS pin. However, when adjusting presets I foresee a case where I'll have both the USB port connected and the internal supply. Would this be a problem for the device or host? I'm assuming not, since GND pin would be connected to both supplies, but I thought I'd double check.

victor1115 commented 7 months ago

Hi Catalin, On the current revision it is NOT possible to supply power via USB and VBUS concurrently. This issue will be fixed on the next revision of the board.

CatalinMustata commented 2 months ago

Hey Victor,

Sorry to revive this, but I had to pause my project for a while and I only picked it up again now. I'm trying to figure out the best way to achieve automatic switching between the internal supply and USB power.

The simplest solution I came across was to add a 5V Zener between the internal supply and VBUS - my thinking is that when USB powered VBUS will be roughly a 5V and no current would flow form my internal supply. Do you think this is a good approach? If not, I'm open to any suggestions.

Some other ideas I had were using a PNP transistor with the base connected to VBUS and VSYS connected to its collector or using a logic gate to reading from my internal supply and VBUS (supply & !VBUS) and feeding VSYS.