Arduino Uno Schematic
Overview
In this tutorial, we will build the schematic for the Arduino Uno development board. This tutorial focuses on the schematic only, utilizing the routingDisabled property to bypass PCB trace routing.
We will include the core microcontroller (ATmega328P), the USB-to-serial communication microcontroller (ATmega16U2), a USB Type-B port, crystal oscillators, power decoupling, and pin headers.
📋 Components Checklist
Our schematic will consist of:
- ATmega328P-PU MCU (U1) — The main processor.
- ATmega16U2 MCU (U2) — The USB-to-Serial converter.
- USB Type-B Female Connector (J1) — For programming and power.
- 16MHz Crystal Oscillator (Y1) — Clock source for the main MCU.
- Decoupling Capacitors & Pull-up Resistors — To stabilize power and reset lines.
- Arduino Header Connectors (J2, J3, J4, J5) — Standard pinout headers.
🛠️ Step-by-Step Implementation
Create a new tutorial snippet in your editor or local project workspace and implement the circuit using the code below.
1. Main Schematic Design
We wrap our components inside a <group subcircuit routingDisabled> block to ensure we focus purely on the logical connections and schematic symbols.
ArduinoUno.tsx
import React from "react"
import { useResistor, useCapacitor } from "@tscircuit/core"
export const ArduinoUno = () => {
// Main MCU: ATmega328P (28-pin DIP)
const atmega328p = (
<chip
name="U1"
manufacturerPartNumber="ATMEGA328P-PU"
schPortArrangement={{
leftSide: {
pins: ["pin1", "pin2", "pin3", "pin4", "pin5", "pin6", "pin7", "pin8", "pin9", "pin10", "pin11", "pin12", "pin13", "pin14"],
direction: "top-to-bottom",
},
rightSide: {
pins: ["pin28", "pin27", "pin26", "pin25", "pin24", "pin23", "pin22", "pin21", "pin20", "pin19", "pin18", "pin17", "pin16", "pin15"],
direction: "top-to-bottom",
}
}}
pinLabels={{
pin1: "/RESET",
pin2: "RXD (PD0)",
pin3: "TXD (PD1)",
pin4: "INT0 (PD2)",
pin5: "INT1 (PD3)",
pin6: "T0 (PD4)",
pin7: "VCC",
pin8: "GND",
pin9: "XTAL1",
pin10: "XTAL2",
pin11: "T1 (PD5)",
pin12: "AIN0 (PD6)",
pin13: "AIN1 (PD7)",
pin14: "ICP1 (PB0)",
pin15: "PB1",
pin16: "SS (PB2)",
pin17: "MOSI (PB3)",
pin18: "MISO (PB4)",
pin19: "SCK (PB5)",
pin20: "AVCC",
pin21: "AREF",
pin22: "GND",
pin23: "ADC0 (PC0)",
pin24: "ADC1 (PC1)",
pin25: "ADC2 (PC2)",
pin26: "ADC3 (PC3)",
pin27: "ADC4 (PC4)",
pin28: "ADC5 (PC5)",
}}
schWidth={3}
schHeight={6.5}
schX={0}
schY={0}
/>
)
// USB-to-Serial MCU: ATmega16U2 (32-pin TQFP)
const atmega16u2 = (
<chip
name="U2"
manufacturerPartNumber="ATMEGA16U2-MU"
schPortArrangement={{
leftSide: {
pins: ["pin1", "pin2", "pin3", "pin4", "pin5", "pin6", "pin7", "pin8"],
direction: "top-to-bottom",
},
bottomSide: {
pins: ["pin9", "pin10", "pin11", "pin12", "pin13", "pin14", "pin15", "pin16"],
direction: "left-to-right",
},
rightSide: {
pins: ["pin24", "pin23", "pin22", "pin21", "pin20", "pin19", "pin18", "pin17"],
direction: "top-to-bottom",
},
topSide: {
pins: ["pin32", "pin31", "pin30", "pin29", "pin28", "pin27", "pin26", "pin25"],
direction: "left-to-right",
}
}}
pinLabels={{
pin1: "XTAL1",
pin2: "PC0",
pin3: "GND",
pin4: "VCC",
pin5: "PC2",
pin6: "PD0",
pin7: "PD1",
pin8: "PD2",
pin9: "PD3",
pin10: "PD4",
pin11: "PD5",
pin12: "PD6",
pin13: "PD7",
pin14: "PB0",
pin15: "PB1",
pin16: "PB2",
pin17: "PB3",
pin18: "PB4",
pin19: "PB5",
pin20: "PB6",
pin21: "PB7",
pin22: "PC7",
pin23: "PC6",
pin24: "PC5",
pin25: "PC4",
pin26: "UGND",
pin27: "UCAP",
pin28: "UVCC",
pin29: "D-",
pin30: "D+",
pin31: "UVSS",
pin32: "PC1",
}}
schWidth={4}
schHeight={4.5}
schX={-10}
schY={5}
/>
)
// USB Port (Type B)
const usbPort = (
<chip
name="J1"
manufacturerPartNumber="USB-B"
schPortArrangement={{
leftSide: {
pins: ["pin1", "pin2", "pin3", "pin4"],
direction: "top-to-bottom",
}
}}
pinLabels={{
pin1: "VBUS",
pin2: "D-",
pin3: "D+",
pin4: "GND",
}}
schWidth={1.5}
schHeight={2}
schX={-18}
schY={5}
/>
)
// 16MHz Crystal for U1
const crystal = (
<chip
name="Y1"
manufacturerPartNumber="16MHz-Oscillator"
schPortArrangement={{
leftSide: { pins: ["pin1"] },
rightSide: { pins: ["pin2"] },
}}
pinLabels={{
pin1: "XTAL1",
pin2: "XTAL2",
}}
schWidth={1}
schHeight={1}
schX={-4}
schY={-4}
/>
)
// Arduino Headers
const powerHeader = (
<chip
name="J2"
manufacturerPartNumber="HEADER-8"
schPortArrangement={{
rightSide: {
pins: ["pin1", "pin2", "pin3", "pin4", "pin5", "pin6", "pin7", "pin8"],
direction: "top-to-bottom",
}
}}
pinLabels={{
pin1: "NC",
pin2: "IOREF",
pin3: "RESET",
pin4: "3.3V",
pin5: "5V",
pin6: "GND",
pin7: "GND",
pin8: "VIN",
}}
schWidth={1.2}
schHeight={3}
schX={8}
schY={6}
/>
)
const analogHeader = (
<chip
name="J3"
manufacturerPartNumber="HEADER-6"
schPortArrangement={{
rightSide: {
pins: ["pin1", "pin2", "pin3", "pin4", "pin5", "pin6"],
direction: "top-to-bottom",
}
}}
pinLabels={{
pin1: "A0",
pin2: "A1",
pin3: "A2",
pin4: "A3",
pin5: "A4",
pin6: "A5",
}}
schWidth={1.2}
schHeight={2.2}
schX={8}
schY={1.5}
/>
)
const digitalHeader1 = (
<chip
name="J4"
manufacturerPartNumber="HEADER-8"
schPortArrangement={{
rightSide: {
pins: ["pin1", "pin2", "pin3", "pin4", "pin5", "pin6", "pin7", "pin8"],
direction: "top-to-bottom",
}
}}
pinLabels={{
pin1: "RX<-0",
pin2: "TX->1",
pin3: "D2",
pin4: "D3",
pin5: "D4",
pin6: "D5",
pin7: "D6",
pin8: "D7",
}}
schWidth={1.2}
schHeight={3}
schX={8}
schY={-3}
/>
)
const digitalHeader2 = (
<chip
name="J5"
manufacturerPartNumber="HEADER-10"
schPortArrangement={{
rightSide: {
pins: ["pin1", "pin2", "pin3", "pin4", "pin5", "pin6", "pin7", "pin8", "pin9", "pin10"],
direction: "top-to-bottom",
}
}}
pinLabels={{
pin1: "D8",
pin2: "D9",
pin3: "D10",
pin4: "D11",
pin5: "D12",
pin6: "D13",
pin7: "GND",
pin8: "AREF",
pin9: "SDA",
pin10: "SCL",
}}
schWidth={1.2}
schHeight={3.8}
schX={8}
schY={-7.5}
/>
)
// Passives
const R1 = useResistor("R1", { resistance: "10k" }) // Pull-up for RESET
const C1 = useCapacitor("C1", { capacitance: "100nF" }) // Decoupling capacitor
return (
<group subcircuit routingDisabled>
{/* Active Components */}
{atmega328p}
{atmega16u2}
{usbPort}
{crystal}
{/* Headers */}
{powerHeader}
{analogHeader}
{digitalHeader1}
{digitalHeader2}
{/* Passives */}
<R1 pin1=".U1 .pin1" pin2="net.5V" schX={-3} schY={2} />
<C1 pos="net.5V" neg="net.GND" schX={-3} schY={0.5} />
{/* Basic Traces */}
<trace from=".U1 .pin7" to="net.5V" />
<trace from=".U1 .pin20" to="net.5V" />
<trace from=".U1 .pin8" to="net.GND" />
<trace from=".U1 .pin22" to="net.GND" />
{/* Crystal Osc Connection */}
<trace from=".U1 .pin9" to=".Y1 .pin1" />
<trace from=".U1 .pin10" to=".Y1 .pin2" />
{/* USB-to-Serial Traces */}
<trace from=".J1 .pin1" to="net.5V" />
<trace from=".J1 .pin2" to=".U2 .pin29" />
<trace from=".J1 .pin3" to=".U2 .pin30" />
<trace from=".J1 .pin4" to="net.GND" />
<trace from=".U2 .pin6" to=".U1 .pin2" /> {/* RX -> TX */}
<trace from=".U2 .pin7" to=".U1 .pin3" /> {/* TX -> RX */}
{/* Main MCU Analog Header Traces */}
<trace from=".U1 .pin23" to=".J3 .pin1" />
<trace from=".U1 .pin24" to=".J3 .pin2" />
<trace from=".U1 .pin25" to=".J3 .pin3" />
<trace from=".U1 .pin26" to=".J3 .pin4" />
<trace from=".U1 .pin27" to=".J3 .pin5" />
<trace from=".U1 .pin28" to=".J3 .pin6" />
{/* Main MCU Digital Header Traces */}
<trace from=".U1 .pin2" to=".J4 .pin1" />
<trace from=".U1 .pin3" to=".J4 .pin2" />
<trace from=".U1 .pin4" to=".J4 .pin3" />
<trace from=".U1 .pin5" to=".J4 .pin4" />
<trace from=".U1 .pin6" to=".J4 .pin5" />
<trace from=".U1 .pin11" to=".J4 .pin6" />
<trace from=".U1 .pin12" to=".J4 .pin7" />
<trace from=".U1 .pin13" to=".J4 .pin8" />
<trace from=".U1 .pin14" to=".J5 .pin1" />
<trace from=".U1 .pin15" to=".J5 .pin2" />
<trace from=".U1 .pin16" to=".J5 .pin3" />
<trace from=".U1 .pin17" to=".J5 .pin4" />
<trace from=".U1 .pin18" to=".J5 .pin5" />
<trace from=".U1 .pin19" to=".J5 .pin6" />
{/* Ground headers */}
<trace from="net.GND" to=".J2 .pin6" />
<trace from="net.GND" to=".J2 .pin7" />
<trace from="net.GND" to=".J5 .pin7" />
</group>
)
}
Conclusion
This completes the schematic setup for the Arduino Uno. Since routingDisabled is set to true, the layout compiler skips the routing phases, keeping compilation fast and visual rendering focused purely on schematic symbols.