ATtiny85 Dev Board
Minimal SOIC-8 ATtiny85 board with ICSP header, status LED, and decoupling.
Difficulty: Surface-mount. Estimated build time: about 90 minutes. Estimated parts cost: about US$5.00. 7-line bill of materials. Compare supplier offers when available. A minimal printed circuit board carrying an ATtiny85 in SOIC-8 package, a 6-pin ICSP header for in-system programming, a status LED on PB0, a 100 nF decoupling capacitor on VCC, and a 10 kΩ pull-up on the RESET line.
Solder the ATtiny85
Apply a small amount of flux to the SOIC-8 pads. Tack pin 1 (GND on SOIC orientation—confirm your layout) to anchor the chip, then solder the remaining pins using drag soldering or individual pin reflow. Inspect each joint under magnification. At 1.27 mm pitch, solder bridges between adjacent pins are the most common defect; flux and wick them out if they appear.
Solder passives
Solder the 100 nF decoupling capacitor as close to the ATtiny85 VCC and GND pins as the layout allows—ideally within 2 mm. Solder the 10 kΩ pull-up resistor between the RESET pin and VCC. Without this pull-up, stray noise can trigger spurious resets. Solder the LED current-limit resistor (470 Ω) in series between PB0 and the LED anode.
Fit the ICSP header
Solder the 2×3 2.54 mm ICSP header. The pin order must match the standard AVR ICSP layout: MISO, Vcc, SCK, MOSI, RESET, GND. If you are making a custom PCB, verify the footprint against the ATtiny85 datasheet pinout—the SOIC pin numbering is not the same as the PDIP numbering.
Program via Arduino ISP
Upload the ArduinoISP sketch to an Arduino Uno. Connect the Uno's ICSP header to your board's ICSP header with a ribbon cable. In the Arduino IDE, select Tools > Board > ATtiny85, Clock = 8 MHz (internal), and Programmer = Arduino as ISP. Run Tools > Burn Bootloader first—this sets the clock fuses. Then upload your sketch. A blink on PB0 confirms success.