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Arduino Uno R3: Assembled from Arduino's Open UNO-TH Rev3e Design Files and Flashed over ICSP
MakeMagazinDE (Wikimedia Commons) · CC BY-SA 4.0
Ed

Created by

Ed

2. November 2026FI
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Arduino Uno R3: Assembled from Arduino's Open UNO-TH Rev3e Design Files and Flashed over ICSP

The Arduino Uno R3 is open hardware: Arduino publishes its schematic and board layout. This blueprint builds one from those files, part by part, then loads the firmware into its two processors. Result: an Arduino Uno R3. An ATmega328P (16 MHz, 32 kB flash, 2 kB SRAM, 1 kB EEPROM) runs your programs; an ATmega16U2 turns USB into its serial link. It runs from USB (5.5 V at most) or 6-20 V at the DC jack. Source: Arduino UNO-TH_Rev3e design files and the A000066 schematic and datasheet (Arduino, CC BY-SA). Unknown: how every bought part is made; no public source in hand says. The soldering method is ours. Picture: Wikimedia Commons.
Advanced
1 day

Instructions

1

Get the bare board

Have the two-layer board made to Arduino's UNO-TH_Rev3e board layout (the .brd file of the design files). Check it against the schematic before fitting anything.

Materials for this step:

Printed Circuit BoardPrinted Circuit Board1 UNO-TH Rev3e layout

Tools needed:

Magnifying LoupeMagnifying Loupe
2

Fit the small surface-mount parts

Solder the chip parts to their marked places: resistor arrays RN1 (10K), RN2 and RN4 (1K), RN3 (22R); R1, R2 (1M); capacitors C1, C2, C4-C7, C10 (100n), C3, C8 (1u), C9, C11 (22p); varistors Z1, Z2; ferrite bead L1; inductor L2 (10 uH); diodes D2, D3; LEDs ON (green), L, RX, TX (yellow). Ours: flux, tweezers and hot air or a fine iron, checked under a loupe.

Materials for this step:

Chip Resistor ArrayChip Resistor Array4 RN1-RN4
Chip ResistorChip Resistor2 1M
Ceramic Chip CapacitorCeramic Chip Capacitor11 7x100n, 2x1u, 2x22p
Chip VaristorChip Varistor2 Z1, Z2
Ferrite BeadFerrite Bead1 L1
Surface-Mount InductorSurface-Mount Inductor1 L2
Surface-Mount DiodeSurface-Mount Diode2 D2, D3
Chip LEDChip LED4 1 green, 3 yellow
Solder WireSolder Wire1 a little

Tools needed:

FluxFlux
Fine-Tip TweezersFine-Tip Tweezers
Hot Air Rework StationHot Air Rework Station
Soldering IronSoldering Iron
Magnifying LoupeMagnifying Loupe
3

Fit the power and chip parts

Solder the ATmega16U2 (U3), the 16 MHz resonator Y2 and crystal Y1, the 5 V regulator NCP1117 (U1) and 3.3 V regulator LP2985 (U2), the LMV358 op-amp (U5), the FDN340P transistor (T1), the M7 diode (D1), the 500 mA resettable fuse (F1) and the 47 uF capacitors PC1, PC2 with their polarity as marked.

Materials for this step:

ATmega16U2 MicrocontrollerATmega16U2 Microcontroller1 U3
Piezoelectric Ceramic ResonatorPiezoelectric Ceramic Resonator1 Y2
Quartz CrystalQuartz Crystal1 Y1
Linear Voltage RegulatorLinear Voltage Regulator2 U1 5 V, U2 3.3 V
Op-Amp ICOp-Amp IC1 U5 LMV358
P-Channel MOSFETP-Channel MOSFET1 T1
Surface-Mount DiodeSurface-Mount Diode1 D1 M7
Resettable FuseResettable Fuse1 F1
Polarised Chip CapacitorPolarised Chip Capacitor2 PC1, PC2
Solder WireSolder Wire1 a little

Tools needed:

FluxFlux
Fine-Tip TweezersFine-Tip Tweezers
Hot Air Rework StationHot Air Rework Station
Soldering IronSoldering Iron
Magnifying LoupeMagnifying Loupe
4

Fit the through-hole parts

Solder the USB-B socket (X2), the DC jack (X1), the reset switch, the female headers (one 10-way, two 8-way, one 6-way) and the two 2x3 ICSP headers. Seat the ATmega328P in its place (ZU4).

Materials for this step:

USB-B SocketUSB-B Socket1 X2
DC Barrel JackDC Barrel Jack1 X1
Push ButtonPush Button1 RESET
Pin HeaderPin Header6 10x1, 2x 8x1, 6x1 female; 2x 3x2 ICSP
ATmega328P MicrocontrollerATmega328P Microcontroller1 ZU4
Solder WireSolder Wire1 as needed

Tools needed:

Soldering IronSoldering Iron
5

Flash and check

Check with a meter that 5 V and GND are not shorted. Through the ICSP headers, load the USB-to-serial firmware into the ATmega16U2 and the bootloader into the ATmega328P. Plug in USB: the green ON LED lights, and the blink test in the next step flashes the L LED. Ours: an AVR ISP programmer and a multimeter.

Materials for this step:

Arduino Uno FirmwareArduino Uno Firmware1 download

Tools needed:

MultimeterMultimeter
AVR ISP ProgrammerAVR ISP Programmer
USB-B CableUSB-B Cable
6

The blink test

blink_test.ino: the same check as Arduino's Blink example. Upload it over USB from the Arduino IDE with the board set to Arduino Uno; the L LED on pin 13 turns on for one second and off for one second, over and over. If it does, both processors, the USB link and the bootloader work.
blink_test.inocpp
// blink_test.ino - first check of a newly built Arduino Uno R3.
// The L LED is on digital pin 13 (LED_BUILTIN on the Uno).
void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);  // L on
  delay(1000);
  digitalWrite(LED_BUILTIN, LOW);   // L off
  delay(1000);
}

Tools needed:

USB-B CableUSB-B Cable

Materials

24

Tools Required

8

This blueprint makes

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Arduino Uno R3

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