I have this schematic which is from the USB to UART section of an ESP32 development kit schematic. I'm fairly new to reading schematics and I'm just wondering what a few things are:

  1. The green box
  2. 'ACTIVE' on the suspend pin
  3. Why is one of the resistor values (I'm assuming that's what it is) in green when the rest are blue?

enter image description here

Update: Here is the whole section of the schematic for context:

enter image description here

  • \$\begingroup\$ Welcome to Electrical Engineering. ACTIVE is just a name given to a signal, that might be referenced somewhere else in the schematic, meaning that there is an implicit connection between all the ACTIVE signals. As for the green frame and the green resistor, I have no idea; I guess some more context might help. \$\endgroup\$ Commented May 17, 2021 at 18:03
  • 1
    \$\begingroup\$ These green things are simply to highlight some important points that the schematic designer wanted to highlight. Just like an emphasis put in some text. Perhaps there is extra info in accompanying documents if any. ACTIVE is a net name. \$\endgroup\$
    – Eugene Sh.
    Commented May 17, 2021 at 18:06

2 Answers 2


The green box is just to draw attention to that block of circuitry or indicate visually that those parts are related to each other in some way.

The voltage divider is required to meet the absolute maximum VBUS voltage specification if Vdd or REGIN may be unpowered when VBUS has 5V on it, as explained in the datasheet: enter image description here

The green plus the (NC) beside the 10K resistor may indicate that it is not normally installed (though that is not one of the several usual ways of indicating that fact). It may not be necessary- the SUSPEND and /SUSPEND pins are outputs and are not used on the section of the schematic that you have provided for us, however the net label "ACTIVE" implies that it might be used somewhere else on the full schematic.

  • \$\begingroup\$ thank you for explaining :) \$\endgroup\$
    – beans
    Commented May 17, 2021 at 19:47

The green box shows a simple state machine interface.

  • Vbus is converted from 5V to 3.3V to show a USB cable is connected and powered.
  • RST! Is also an input to permit a push button switch 0V
  • Active is high and could also be with an LED and 1k resistor but otherwise the resistor is an easy test point and optional. Normally No Connection, NC
  • Logic diagrams are supposed to be “logical” but depends who did it.

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