How to Use ATTiny85: Examples, Pinouts, and Specs

The ATTiny85 is a small, low-power microcontroller from Atmel's AVR family, designed for embedded systems and DIY electronics projects. It features an 8-bit architecture, 8 KB of flash memory, 512 bytes of SRAM, and 6 I/O pins. Its compact size and ease of programming make it a popular choice for applications where space and power efficiency are critical.

• Wearable electronics
• IoT (Internet of Things) devices
• LED control and lighting systems
• Sensor-based projects
• Small robotics and automation systems
• Prototyping and hobbyist projects

The ATTiny85 is a versatile microcontroller with the following key specifications:

The ATTiny85 has 8 pins, with the following configuration:

1. Power Supply: Connect the VCC pin to a power source (2.7V to 5.5V) and the GND pin to ground.
2. Programming: Use an ISP (In-System Programmer) such as an Arduino UNO or a dedicated USB programmer to upload code to the ATTiny85.
3. I/O Connections: Connect sensors, actuators, or other peripherals to the GPIO pins (PB0 to PB5) as needed.
4. Clock Source: The ATTiny85 can use its internal 8 MHz oscillator or an external clock source for higher precision.

• Pull-up Resistor on RESET Pin: If the RESET pin is used as a GPIO, disable the reset functionality in the fuse settings. Otherwise, use a pull-up resistor (10 kΩ) to prevent accidental resets.
• Decoupling Capacitor: Place a 0.1 µF ceramic capacitor between VCC and GND to stabilize the power supply.
• Programming Voltage: Ensure the programmer's voltage matches the operating voltage of the ATTiny85.
• Pin Limitations: Avoid exceeding the maximum current rating of 40 mA per pin or 200 mA for the entire chip.

The following example demonstrates how to blink an LED connected to PB0 using the Arduino IDE:

1. Connect the Arduino UNO to the ATTiny85 as follows:
   • Arduino UNO Pin 10 → ATTiny85 Pin 1 (RESET)
   • Arduino UNO Pin 11 → ATTiny85 Pin 5 (MOSI)
   • Arduino UNO Pin 12 → ATTiny85 Pin 6 (MISO)
   • Arduino UNO Pin 13 → ATTiny85 Pin 7 (SCK)
   • Arduino UNO GND → ATTiny85 Pin 4 (GND)
   • Arduino UNO 5V → ATTiny85 Pin 8 (VCC)
2. Connect an LED with a 220 Ω resistor to PB0 (Pin 5) of the ATTiny85.

// Blink an LED connected to PB0 (Pin 5) of the ATTiny85

void setup() {
  pinMode(0, OUTPUT); // Set PB0 (digital pin 0) as an output
}

void loop() {
  digitalWrite(0, HIGH); // Turn the LED on
  delay(1000);           // Wait for 1 second
  digitalWrite(0, LOW);  // Turn the LED off
  delay(1000);           // Wait for 1 second
}

1. Open the Arduino IDE and install the "ATTinyCore" library via the Boards Manager.
2. Select "ATTiny85" as the board and configure the clock settings (e.g., 8 MHz internal).
3. Upload the code using the "Arduino as ISP" programmer.

1. Problem: The ATTiny85 is not detected by the programmer.

   • Solution: Check the wiring between the programmer and the ATTiny85. Ensure the RESET pin is connected correctly.

2. Problem: The LED does not blink.

   • Solution: Verify the LED and resistor connections. Ensure the correct pin is used in the code.

3. Problem: The ATTiny85 is not running at the expected clock speed.

   • Solution: Check the fuse settings and ensure the correct clock source is selected.

4. Problem: Excessive power consumption in low-power applications.

   • Solution: Use the ATTiny85's sleep modes and disable unused peripherals in the code.

• Q: Can the ATTiny85 be reprogrammed multiple times?
  A: Yes, the ATTiny85 supports up to 10,000 write/erase cycles for its flash memory.

• Q: Can I use the ATTiny85 without an external clock?
  A: Yes, the ATTiny85 has an internal 8 MHz oscillator, which is sufficient for most applications.

• Q: How do I use the EEPROM on the ATTiny85?
  A: The EEPROM can be accessed using the EEPROM library in the Arduino IDE for storing non-volatile data.

• Q: What is the maximum current the ATTiny85 can source or sink?
  A: Each pin can handle up to 40 mA, with a total maximum of 200 mA for the entire chip.