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I'm trying to recreate the Arduino UNO in order to be good at PCB design via EasyEDA or Altium. I have recreated the Arduino Uno schematic and design but it is hard for me to figure out few things (please refer to the image.)

  1. Why are those parts left aside from the main microcontroller assembly (denoted by numbers)
  2. I have figured out how to connect those connections using an eye tool or net wiring, but could not figure out what were those numbers (pointed by arrowheads) in resistors
  3. If anything that I should be reading or referred to draw PCBs

enter image description here

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    \$\begingroup\$ The hint is 'RN' - resistor network. It might be advisable to use separate resistors. Also consider the component sizes - production boards (ie made by machine) will usually be designed with smaller parts where suitable (ie 0402 size resistors, caps etc). 0402 is getting a bit too small to manually handle, so my suggestion is to use 0603 or larger components where applicable. As well, resistor networks may not be as easily available (to the hobbyist) as compared with 'normal' resistors. \$\endgroup\$
    – Kartman
    Commented Jul 25, 2021 at 7:15
  • \$\begingroup\$ Thank you very much! @Kartman Appreciate it. \$\endgroup\$ Commented Jul 25, 2021 at 19:20

2 Answers 2

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  1. The sections of the schematic you have numbered one to 7, are simply a way of making the schematic more readable. Even though they look separate, they are interconnected with the MCU by net-names (Vin, +5V, GND, etc..). The resistors in box "5" are just left over resistors not used, but still a part of the resistor network.

  2. As @wouter-van-ooijen says the resistors are actually a "resistor network"; a single component containing multiple resistors. See the image below of the two types of resistor networks available; yours are most likely the bottom one.

Resistor network

  1. There are many good online resources online; one of my favourites is Chris Gammel's Getting to Blinky (even though it is for KiCad, but the principles are the same)
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  • \$\begingroup\$ Thank you very much! @Jakob Halskov Appreciate it. \$\endgroup\$ Commented Jul 25, 2021 at 19:21
  • \$\begingroup\$ You are Welcome! Please mark my or Wouter’s answer as accepted if you are happy with it. \$\endgroup\$ Commented Jul 26, 2021 at 7:23
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This board/circuit uses a resistor pack. Those numbers are the pin numbers of the specific resistors within the pack.

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  • \$\begingroup\$ Thank you very much! @Wouter van Ooijen Appreciate it. \$\endgroup\$ Commented Jul 25, 2021 at 19:21

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