Arduino Uno Reference Schematic

Overview

This tutorial builds a schematic-only Arduino Uno style reference in tscircuit. It focuses on the recognizable functional blocks instead of PCB routing:

ATmega328P microcontroller core
USB serial bridge for uploads and serial monitor traffic
5 V, 3.3 V, VIN, and ground rails
reset pull-up, reset button, and auto-reset capacitor
16 MHz clock and load capacitors
digital, analog, power, and ICSP headers
built-in L LED on D13

Use the official Arduino Uno Rev3 documentation and schematic when adapting this example to a production-compatible design:

Full Schematic

The snippet below keeps the board schematic-only with routingDisabled, then names the functional nets so each Uno block is easy to review.

export default () => (
<board width="120mm" height="86mm" routingDisabled>
  <net name="VIN" />
  <net name="VUSB" />
  <net name="V5" />
  <net name="V3_3" />
  <net name="GND" />
  <net name="RESET" />
  <net name="AREF" />
  <net name="XTAL1" />
  <net name="XTAL2" />
  <net name="DTR" />
  <net name="USB_D_PLUS" />
  <net name="USB_D_MINUS" />

  <chip
    name="U_ATMEGA328P"
    footprint="dip28"
    schX={0}
    schY={0}
    schWidth="36mm"
    schHeight="56mm"
    pinLabels={{
      pin1: "RESET",
      pin2: "D0_RX",
      pin3: "D1_TX",
      pin4: "D2",
      pin5: "D3_PWM",
      pin6: "D4",
      pin7: "VCC",
      pin8: "GND",
      pin9: "XTAL1",
      pin10: "XTAL2",
      pin11: "D5_PWM",
      pin12: "D6_PWM",
      pin13: "D7",
      pin14: "D8",
      pin15: "D9_PWM",
      pin16: "D10_SS",
      pin17: "D11_MOSI",
      pin18: "D12_MISO",
      pin19: "D13_SCK",
      pin20: "AVCC",
      pin21: "AREF",
      pin22: "AGND",
      pin23: "A0",
      pin24: "A1",
      pin25: "A2",
      pin26: "A3",
      pin27: "A4_SDA",
      pin28: "A5_SCL",
    }}
    schPinArrangement={{
      leftSide: {
        direction: "top-to-bottom",
        pins: ["RESET", "D0_RX", "D1_TX", "D2", "D3_PWM", "D4", "D5_PWM", "D6_PWM", "D7"],
      },
      rightSide: {
        direction: "top-to-bottom",
        pins: [
          "D8",
          "D9_PWM",
          "D10_SS",
          "D11_MOSI",
          "D12_MISO",
          "D13_SCK",
          "A0",
          "A1",
          "A2",
          "A3",
          "A4_SDA",
          "A5_SCL",
        ],
      },
      topSide: {
        direction: "left-to-right",
        pins: ["VCC", "AVCC", "AREF"],
      },
      bottomSide: {
        direction: "left-to-right",
        pins: ["GND", "AGND", "XTAL1", "XTAL2"],
      },
    }}
    connections={{
      VCC: "net.V5",
      AVCC: "net.V5",
      GND: "net.GND",
      AGND: "net.GND",
      AREF: "net.AREF",
      RESET: "net.RESET",
      XTAL1: "net.XTAL1",
      XTAL2: "net.XTAL2",
      D0_RX: "net.D0_RX",
      D1_TX: "net.D1_TX",
      D2: "net.D2",
      D3_PWM: "net.D3_PWM",
      D4: "net.D4",
      D5_PWM: "net.D5_PWM",
      D6_PWM: "net.D6_PWM",
      D7: "net.D7",
      D8: "net.D8",
      D9_PWM: "net.D9_PWM",
      D10_SS: "net.D10_SS",
      D11_MOSI: "net.D11_MOSI",
      D12_MISO: "net.D12_MISO",
      D13_SCK: "net.D13_SCK",
      A0: "net.A0",
      A1: "net.A1",
      A2: "net.A2",
      A3: "net.A3",
      A4_SDA: "net.A4_SDA",
      A5_SCL: "net.A5_SCL",
    }}
  />

  <connector
    name="J_USB"
    standard="usb_c"
    schX={-56}
    schY={20}
    pinLabels={{ pin1: "VBUS", pin2: "D-", pin3: "D+", pin4: "GND" }}
    connections={{
      VBUS: "net.VUSB",
      "D-": "net.USB_D_MINUS",
      "D+": "net.USB_D_PLUS",
      GND: "net.GND",
    }}
  />
  <fuse
    name="F_USB"
    footprint="0603"
    schX={-38}
    schY={20}
    connections={{ pin1: "net.VUSB", pin2: "net.V5" }}
  />
  <chip
    name="U_USB_SERIAL"
    footprint="soic16"
    schX={-28}
    schY={4}
    schWidth="24mm"
    schHeight="30mm"
    pinLabels={{
      pin1: "VCC",
      pin2: "GND",
      pin3: "TXD",
      pin4: "RXD",
      pin5: "DTR",
      pin6: "D+",
      pin7: "D-",
    }}
    connections={{
      VCC: "net.V5",
      GND: "net.GND",
      TXD: "net.D0_RX",
      RXD: "net.D1_TX",
      DTR: "net.DTR",
      "D+": "net.USB_D_PLUS",
      "D-": "net.USB_D_MINUS",
    }}
  />

  <chip
    name="U_5V_REG"
    footprint="sot223"
    schX={-46}
    schY={-24}
    pinLabels={{ pin1: "GND", pin2: "VOUT", pin3: "VIN" }}
    connections={{ VIN: "net.VIN", VOUT: "net.V5", GND: "net.GND" }}
  />
  <chip
    name="U_3V3_REG"
    footprint="sot23-5"
    schX={-22}
    schY={-24}
    pinLabels={{ pin1: "VIN", pin2: "GND", pin3: "EN", pin4: "NC", pin5: "VOUT" }}
    connections={{ VIN: "net.V5", VOUT: "net.V3_3", GND: "net.GND", EN: "net.V5" }}
  />
  <capacitor
    name="C_5V_IN"
    capacitance="10uF"
    footprint="0805"
    schX={-58}
    schY={-34}
    connections={{ pos: "net.VIN", neg: "net.GND" }}
  />
  <capacitor
    name="C_5V_OUT"
    capacitance="10uF"
    footprint="0805"
    schX={-34}
    schY={-34}
    connections={{ pos: "net.V5", neg: "net.GND" }}
  />
  <capacitor
    name="C_3V3_OUT"
    capacitance="10uF"
    footprint="0805"
    schX={-12}
    schY={-34}
    connections={{ pos: "net.V3_3", neg: "net.GND" }}
  />

  <crystal name="Y_16MHZ" frequency="16MHz" loadCapacitance="18pF" footprint="hc49" schX={4} schY={-38} />
  <capacitor
    name="C_XTAL1"
    capacitance="22pF"
    footprint="0402"
    schX={-8}
    schY={-48}
    connections={{ pos: "net.XTAL1", neg: "net.GND" }}
  />
  <capacitor
    name="C_XTAL2"
    capacitance="22pF"
    footprint="0402"
    schX={16}
    schY={-48}
    connections={{ pos: "net.XTAL2", neg: "net.GND" }}
  />
  <trace from=".Y_16MHZ > .pin1" to="net.XTAL1" />
  <trace from=".Y_16MHZ > .pin2" to="net.XTAL2" />

  <resistor
    name="R_RESET"
    resistance="10k"
    footprint="0402"
    schX={-16}
    schY={34}
    connections={{ pos: "net.V5", neg: "net.RESET" }}
  />
  <capacitor
    name="C_AUTO_RESET"
    capacitance="100nF"
    footprint="0402"
    schX={-32}
    schY={34}
    connections={{ pos: "net.DTR", neg: "net.RESET" }}
  />
  <pushbutton name="SW_RESET" schX={2} schY={34} connections={{ pin1: "net.RESET", pin2: "net.GND" }} />
  <capacitor
    name="C_AREF"
    capacitance="100nF"
    footprint="0402"
    schX={20}
    schY={34}
    connections={{ pos: "net.AREF", neg: "net.GND" }}
  />

  <led name="LED_L" color="yellow" footprint="0603" schX={34} schY={16} />
  <resistor
    name="R_LED_L"
    resistance="1k"
    footprint="0402"
    schX={48}
    schY={16}
    connections={{ pos: "net.D13_SCK", neg: ".LED_L > .anode" }}
  />
  <trace from=".LED_L > .cathode" to="net.GND" />

  <connector
    name="J_DIGITAL_0_7"
    schX={56}
    schY={36}
    pinLabels={{
      pin1: "D0/RX",
      pin2: "D1/TX",
      pin3: "D2",
      pin4: "D3 PWM",
      pin5: "D4",
      pin6: "D5 PWM",
      pin7: "D6 PWM",
      pin8: "D7",
    }}
    connections={{
      "D0/RX": "net.D0_RX",
      "D1/TX": "net.D1_TX",
      D2: "net.D2",
      "D3 PWM": "net.D3_PWM",
      D4: "net.D4",
      "D5 PWM": "net.D5_PWM",
      "D6 PWM": "net.D6_PWM",
      D7: "net.D7",
    }}
  />
  <connector
    name="J_DIGITAL_8_13"
    schX={56}
    schY={8}
    pinLabels={{
      pin1: "D8",
      pin2: "D9 PWM",
      pin3: "D10 SS",
      pin4: "D11 MOSI",
      pin5: "D12 MISO",
      pin6: "D13 SCK",
      pin7: "GND",
      pin8: "AREF",
      pin9: "SDA",
      pin10: "SCL",
    }}
    connections={{
      D8: "net.D8",
      "D9 PWM": "net.D9_PWM",
      "D10 SS": "net.D10_SS",
      "D11 MOSI": "net.D11_MOSI",
      "D12 MISO": "net.D12_MISO",
      "D13 SCK": "net.D13_SCK",
      GND: "net.GND",
      AREF: "net.AREF",
      SDA: "net.A4_SDA",
      SCL: "net.A5_SCL",
    }}
  />
  <connector
    name="J_ANALOG"
    schX={56}
    schY={-18}
    pinLabels={{ pin1: "A0", pin2: "A1", pin3: "A2", pin4: "A3", pin5: "A4 SDA", pin6: "A5 SCL" }}
    connections={{
      A0: "net.A0",
      A1: "net.A1",
      A2: "net.A2",
      A3: "net.A3",
      "A4 SDA": "net.A4_SDA",
      "A5 SCL": "net.A5_SCL",
    }}
  />
  <connector
    name="J_POWER"
    schX={-58}
    schY={-8}
    pinLabels={{ pin1: "RESET", pin2: "3V3", pin3: "5V", pin4: "GND", pin5: "GND", pin6: "VIN" }}
    connections={{ RESET: "net.RESET", "3V3": "net.V3_3", "5V": "net.V5", GND: "net.GND", VIN: "net.VIN" }}
  />
  <connector
    name="J_ICSP"
    schX={34}
    schY={-36}
    pinLabels={{ pin1: "MISO", pin2: "V5", pin3: "SCK", pin4: "MOSI", pin5: "RESET", pin6: "GND" }}
    connections={{
      MISO: "net.D12_MISO",
      V5: "net.V5",
      SCK: "net.D13_SCK",
      MOSI: "net.D11_MOSI",
      RESET: "net.RESET",
      GND: "net.GND",
    }}
  />
</board>
)

Block Review

Block	What to verify
ATmega328P	`VCC`, `AVCC`, `GND`, `AGND`, `AREF`, reset, oscillator, digital IO, and analog IO are all named.
USB serial	USB data connects to the serial bridge, and serial bridge `TXD`/`RXD` cross to `D0_RX`/`D1_TX`.
Power	USB power, VIN, 5 V regulator, 3.3 V regulator, and decoupling capacitors are reviewable as separate rails.
Clock	`XTAL1` and `XTAL2` connect to a 16 MHz crystal and two load capacitors to ground.
Reset	`RESET` has a pull-up, pushbutton path to ground, and DTR auto-reset capacitor.
Headers	Digital, analog, power, and ICSP headers expose the same functional groups users expect from an Uno.

Why This Is Schematic-Only

The archived bounty asks for an Arduino Uno schematic, not a routed board. Keeping the example schematic-only makes it easier to inspect the logical nets and to use the circuit as a reference when creating a board-specific layout later.

For a manufacturable Uno-compatible board, replace the generic footprints with the exact sourced components, verify USB connector pinout, add board geometry, place headers on the Uno mechanical grid, and route the 16 MHz crystal and USB signals with their layout constraints.

Overview​

Full Schematic​

Block Review​

Why This Is Schematic-Only​

Overview

Full Schematic

Block Review

Why This Is Schematic-Only