Hi, i recently purchased a raspberry pi pico for a midi project im doing, and i was wondering if it would be possible to wire an led in reverse, so instead of going gpio-led-ground i could go 3.3v-led-gpio. Then by switching the gpio, i am essentially turning on and off ground. The reason for this would be the max combined current of the gpio pins is only 50mah, and the 3.3v source is 300mah, so it would allow me to power more leds simultaneously… i hope this makes sense 
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Hi Mathew
I think you will find the max current for the GPIO is 50mA source AND/OR sink. That is 50mA in both directions.
Cheers Bob
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Hey Matthew and Bob,
Spot on:
I wouldn’t go anywhere near 50mA though, the recommended “healthy” max sink current for the Pi is generally around 16mA from memory. They tend to get a “little warm” if you sink more than that continuously:
You’re going to need to use a MOSFET, relay, or something else to wrangle higher current off the GPIO of the Pi, most GPIO are only intended for signal transmission or very low current loads.
This should make it easy 
:
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I’d love to see it when you’re done.
Love me anything audio/midi related.
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From the RP2040 datasheet.
Note: The default drive can be increased up to 12mA by changing registers values. Low level access.
Sink or source.
If every pin was driving 4mA the total would be over 100mA.
If you need to drive a lot of LEDs suggest looking at specialised chips designed to do that.
Really depends on what you want to do.
Drag too much current through the Pico and it will die quickly.
Switching 3v3 or GND to a LED does not change anything.
Regards
Jim
PS protection of the microcontroller is high design priority.
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