ATtiny85 Digispark & 8-bit AVR

Digital I/O Pins (P0 - P5)

6 multi-function pins operating at 5V logic. Up to 40mA source/sink per pin.

• P0 (PB0) hosts hardware I2C SDA and SPI MOSI with PWM capability
• P1 (PB1) connected to onboard user LED, hosts SPI MISO and PWM output
• P5 (PB5) functions as the hardware RESET pin by default (weak I/O unless fused)

Analog Input Channels (ADC1 - ADC3)

4 high-speed 10-bit analog-to-digital converter channels reading voltages from 0 to 5V.

• Pin P2 = ADC1, Pin P3 = ADC3, Pin P4 = ADC2, Pin P5 = ADC0
• Selectable internal 1.1V and 2.56V bandgap voltage references for precision measurement
• Hardware analog comparator with configurable interrupt threshold

USB Data Lines & Power Distribution

V-USB software communication pins and onboard voltage regulation rails.

• Pin P3 is tied to USB D+ via a 1.5k pull-up resistor (avoid heavy loads at boot)
• Pin P4 is tied to USB D- through series zener clamping diodes
• VIN pin accepts 7V to 12V; 5V pin supplies regulated 5V power up to 500mA

V-USB Virtual HID

Pins P3 (D+) & P4 (D-)

Bit-banged USB 1.1 protocol sending keystrokes, mouse clicks, and raw HID reports to any host operating system.

Software UART Serial

Any Available GPIO

Bit-banged serial communications via the DigiCDC or TinyDebugSerial libraries up to 115200 baud.

USI Two-Wire (I2C)

Pin P0 (SDA) & Pin P2 (SCL)

Universal Serial Interface operating in TWI mode to communicate with OLED screens and I2C sensors.

USI SPI Protocol

Pin P0 (DO), P1 (DI), P2 (SCK)

Hardware synchronous serial interface running up to 2 MHz for shift registers and RF transceivers.

Hardware PWM (x3)

Pins P0, P1, P4

8-bit timer pulse-width modulation for smooth LED fading and miniature servo angle positioning.

Micronucleus Bootloader

USB Bus Enumeration

Innovative 1.5 KB USB bootloader that polls for code uploads for 5 seconds after insertion.

Emulate standard USB keyboard strokes using DigiKeyboard.h to automate administrative setup tasks or security penetration testing demonstrations.

Pro tip: Always prepend a 1000ms delay at the start of your sketch to allow the OS USB HID driver enumeration to complete.

Unlike traditional Arduinos, you must press "Upload" in the Arduino IDE FIRST, and then physically insert the Digispark into the USB port when prompted.

Pro tip: If uploading fails, use a USB 2.0 hub; modern USB 3.2 ports sometimes fail to enumerate the software-bit-banged V-USB handshake.

Use the optimized TinyWireM library with SSD1306 displays to render graphics and readouts within the constrained 512 bytes of SRAM.

Pro tip: Use text-only rendering without a full 1024-byte framebuffer, as the ATtiny85 only has 512 bytes of total RAM.

Disable the ADC, power-down the internal PLL, and enter Power-down sleep mode. The ATtiny85 draws less than 5 µA, running for years on a coin cell.

Pro tip: Desolder the onboard 5V regulator and power LED to achieve true microamp-level current draw on CR2032 cells.

Pin P5 is hardwired as RESET. By programming the RSTDISBL fuse via high-voltage serial programming, P5 unlocks as a full 6th GPIO pin.

Pro tip: Warning: Disabling the reset pin prevents future USB bootloader flashing unless reset with an HV programmer.

Store persistent device configuration settings and keystroke payload scripts across reboots in 512 bytes of internal non-volatile EEPROM.

Pro tip: Use EEPROM to maintain an "already-executed" flag so BadUSB payloads execute only once per target machine.

BadUSB & Automated Keystroke Payloads

Injects pre-programmed keystroke scripts into host PCs at lightning speeds disguised as a standard USB keyboard for authorized penetration tests.

Physical Macro Pads & Media Controllers

Connects rotary encoders and pushbuttons to execute complex hotkeys (mute, pause, volume control, app launching) via USB HID.

Wearable Electronics & Cosplay Miniatures

Fits inside rings, jewelry, and props to drive smooth pulsing NeoPixel LEDs or read miniature tilt/vibration switches.

Single-Purpose Power & Logic Monitors

Operates as a watchdog timer, power sequencer, or smart battery voltage cut-off switch in tight electronics enclosures.

// ATtiny85 Digispark - USB Keystroke Automation
#include "DigiKeyboard.h"

void setup() {
  // Allow OS 2 seconds to enumerate USB HID driver
  DigiKeyboard.delay(2000);
  DigiKeyboard.sendKeyStroke(0); // Clear keyboard buffer

  // Open Windows Run dialog: Win + R
  DigiKeyboard.sendKeyStroke(KEY_R, MOD_GUI_LEFT);
  DigiKeyboard.delay(400);

  // Type command and press ENTER
  DigiKeyboard.print("notepad.exe");
  DigiKeyboard.sendKeyStroke(KEY_ENTER);
  DigiKeyboard.delay(800);

  // Print message directly to screen
  DigiKeyboard.println("Hello from Volt X ATtiny85 Digispark!");
  DigiKeyboard.println("Automated keystroke injection complete.");
}

void loop() {
  // Blink onboard LED (PB1) to indicate script finished
  digitalWrite(1, HIGH);
  DigiKeyboard.delay(500);
  digitalWrite(1, LOW);
  DigiKeyboard.delay(500);
}

// ATtiny85 - Analog LDR Reading & PWM LED Dimmer
const int ldrPin = 2; // P2 (ADC1)
const int ledPin = 0; // P0 (PWM)

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Read analog light level (0 - 1023)
  int lightLevel = analogRead(ldrPin);

  // Map sensor input to 8-bit PWM brightness (0 - 255)
  int brightness = map(lightLevel, 0, 1023, 255, 0);
  brightness = constrain(brightness, 0, 255);

  analogWrite(ledPin, brightness);
  delay(20);
}