Arduino Uno Schematic
Overview
This tutorial builds a schematic-only Arduino Uno style reference circuit in tscircuit. It follows the main blocks from the Arduino UNO R3 hardware page and Arduino UNO reference schematic:
- ATmega328P microcontroller with the Arduino digital and analog pin nets
- 16 MHz clock network and reset pull-up
- USB-to-serial bridge connected to D0/RX and D1/TX
- USB, barrel jack, 5 V, and 3.3 V power inputs
- ICSP, power, analog, and digital shield headers
- D13 user LED and basic decoupling capacitors
Use this schematic as a readable starting point before you add an exact PCB outline, Uno shield spacing, or the full automatic USB/external power-selection circuit.
Schematic
Block Notes
| Block | What it models |
|---|---|
| Microcontroller | U1 is the ATmega328P. Its labeled nets match the Uno shield-facing pins: D0_RX through D13_SCK, A0 through A5_SCL, RESET, AREF, V5, and GND. |
| USB programming | U2 represents the ATmega16U2 USB-to-serial bridge. Its TX/RX nets cross to the ATmega328P UART nets, and DTR couples through C3 for auto-reset during upload. |
| Clock and reset | Y1, C1, and C2 form the 16 MHz clock network. R1 holds reset high and SW1 pulls reset low. |
| Power | J_USB, F1, J_PWRIN, D1, U3, and U4 show the USB input, external input, 5 V regulator, and 3.3 V regulator. |
| Headers | The power, analog, digital, and ICSP headers expose the same logical nets a shield expects from an Uno. |
Pin Mapping
| Arduino pin | ATmega328P port label | Net in this schematic |
|---|---|---|
| D0 / RX | PD0 | D0_RX |
| D1 / TX | PD1 | D1_TX |
| D2 | PD2 | D2 |
| D3 / PWM | PD3 | D3_PWM |
| D4 | PD4 | D4 |
| D5 / PWM | PD5 | D5_PWM |
| D6 / PWM | PD6 | D6_PWM |
| D7 | PD7 | D7 |
| D8 | PB0 | D8 |
| D9 / PWM | PB1 | D9_PWM |
| D10 / SS / PWM | PB2 | D10_SS |
| D11 / MOSI / PWM | PB3 | D11_MOSI |
| D12 / MISO | PB4 | D12_MISO |
| D13 / SCK | PB5 | D13_SCK |
| A0-A3 | PC0-PC3 | A0 through A3 |
| A4 / SDA | PC4 | A4_SDA |
| A5 / SCL | PC5 | A5_SCL |
Extending the Example
For a production-compatible Uno clone, keep this schematic view and add:
- the exact Uno shield outline and offset header spacing in PCB view
- the full comparator and MOSFET power-source selection circuit
- USB ESD protection and the complete ATmega16U2 support network
- manufacturer-approved footprints and part numbers for every connector