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I need to know how the LED light of a USB card reader that indicates the data transfer works?

Is it possible to create such a light using transistors and putting that circuit parallelly with a data cable connected to a USB storage drive?

Card reader schematic

In this diagram how that LED connected with the GPIO0 pin works?

I was talking about the light that blinks in this video.

https://drive.google.com/file/d/1odw-TqbCfqCP_JEQI6smA7dSSWmZ1QNp/view?usp=drive_link

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  • $\begingroup$ the LED lights when GPIO0 is at a positive voltage ... current flows through the resistor and through the LED, which causes the LED to light $\endgroup$
    – jsotola
    Commented Jul 27 at 13:38
  • $\begingroup$ How can we build that using any other IC? $\endgroup$
    – user10897549
    Commented Jul 30 at 9:57

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The pins the LEDs are connected to are labeled GPIO, or general purpose input/output.

This means there is some logic inside that decides when to put the pin in a HIGH state. That will put the pin at the same voltage level as VCC which then flows through the resistor and the LED and to ground. This logic will be tied to the logic that translated the USB mass storage protocol into the SD card protocol.

The USB protocol sends a lot of messages back and forth even when idle so any device that doesn't snoop on and interpret the USB protocol is going to end up always lit.

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  • $\begingroup$ So, how can we build that using any IC or transistor? $\endgroup$
    – user10897549
    Commented Jul 30 at 9:56

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