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After watching many videos I would like to try to make my own ESP32 driven christmas LED display. But a few things aren't clear:

  1. Are all GPIO pins available to me to drive LED's ? (Many video's/articles talk about alternate labels / roles for these pins). How many LED's can one ESP32 control?

  2. Do I need to put inline resistors with each LED ? There seems to be lots of ESP32 board variations, is there such a think as an LED specific board with resistors already soldered on the board? (Trying to avoid too much learning)

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    \$\begingroup\$ There are a large number of ESP32 microprocessors so the number of GPIO pins can vary. The purpose of GPIO is to allow the user to customize their own application.... so ,yes, I can't see why you wouldn't be able to drive all of your LEDs with the GPIO pins. I doubt you will find a board that only serves to drive LEDs because that would limit the user from utilizing the ESP32 to its fullest potential. That would be like buying a car only so that you can play music. \$\endgroup\$
    – user319168
    Dec 5, 2023 at 17:54

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  1. A blanket statement of "No", because some pins are reserved for bootstraps, i.e. configuring from where the MCU boots and how. These may need to be pulled up or down during the MCU reset so an incorrect load on them makes the MCU to boot incorrectly by trying to boot from some place you don't want it to.

Different models have different amount of GPIO pins, but this is largely irrelevant for many reasons. First is that you seem to be trying to connect all free IO pins to LEDs, so you likely have too much load on the IO pins and you can't have that much load. Second reason is, don't try to run one LED per IO pin to begin with. Using an addressable LED strip, a single IO pin can send data to hundreds of RGB LEDs in chain. I once analyzed some RGB controller that came with a cheap PC case and it tried to control 600 LEDs.

  1. Yes, a resistor is always needed between an IO pin and a LED, to prevent overcurrent from damaging and burning out either the IO pin or the LED. I have not seen a board made for the purpose of directly connecting to LEDs by having onboard resistors, but such a thing could exist. I just don't see why anyone would have made one for such a specific purpose, but as I mentioned already, it may not be a good idea to load all IO pins with LEDs.
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  • \$\begingroup\$ I'm not sure I understand your point about too much load - would 16 leds (one for each GPIO output) be too much for the mcu to handle? Or do you mean if I had lots of them in parallel on a single GPIO pin? \$\endgroup\$
    – TSG
    Dec 5, 2023 at 18:42
  • \$\begingroup\$ @TSG that will depend on a lot of things - the MCU and how much you want to draw current from it, how much current for each LED. There are limitations and sometimes they are not clearly documented. You might have a maximum per single pin. You might have a maximum for a group of pins, which limits how much current is left per 4 LEDs on same group. You might have a maximum for all GPIO pins globally. Same for the VDD/VSS pins, per-pin, per-group, per-total. How much current you want for each of the 16 LEDs, or which exact LED and ESP32 module you use so we can read the data sheets? \$\endgroup\$
    – Justme
    Dec 5, 2023 at 18:58
  • \$\begingroup\$ I don't have a specific ESP32 or LED in mind yet. I'm just at the theoretical level right now. \$\endgroup\$
    – TSG
    Dec 19, 2023 at 15:36

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