Looking for a project using ATTINY85 to generate 1 pulse per second using a 32Khz clock crystal
ChatGPT said:
Creating a 1 pulse per second (1Hz) signal using an ATtiny85 with a 32.768 kHz crystal is a great project. The 32.768 kHz crystal is commonly used in real-time clocks (RTC), so it's perfect for this kind of project.
Here’s an outline for how to achieve the goal of generating 1 pulse per second with an ATtiny85:
Components:
- ATtiny85 microcontroller
- 32.768 kHz crystal oscillator (often used in RTCs)
- Two capacitors (typically 12-22pF for the crystal, depending on specifications)
- Resistors for stabilization (optional)
- LED or another output to display the pulse
Step-by-Step Guide:
1. Crystal Oscillator Setup:
- The ATtiny85 doesn't have a built-in 32.768 kHz crystal oscillator. To use this crystal, you can configure the ATtiny85 to run the crystal on an external clock input.
- You'll need to connect the crystal to the external pins of the ATtiny85. You may need two capacitors (typically around 12-22pF) connected to each pin of the crystal to stabilize the signal.
2. ATtiny85 Fuses:
- Set the fuses of the ATtiny85 to enable the external clock (32.768 kHz crystal) to be the system clock source. This step can be done via the avrdude tool or using an Arduino IDE with the ATtiny core.
3. Counter Setup:
- Since the 32.768 kHz clock provides 32,768 pulses per second, you need to divide this down to create a 1 Hz signal.
- You can use the ATtiny85's internal Timer/Counter module to divide the 32.768 kHz clock down to a 1 Hz signal.
A simple method would be to set the timer to overflow after every 32,768 pulses (this corresponds to 1 second). This is done using the Timer's prescaler and counter settings.
4. Timer Code:
Here's a rough code example for generating a 1Hz pulse output on a pin (e.g., PB0) using the ATtiny85 and 32.768 kHz crystal:
cpp
Copy
#include <avr/io.h>
#include <avr/interrupt.h>
// Set the clock prescaler for the 32.768kHz crystal
#define F_CPU 32768UL // Define the clock frequency
void setup() {
// Set PB0 (pin 5 on ATtiny85) as an output
DDRB |= (1 << PB0);
// Set Timer0 to overflow every 32,768 cycles (1 second)
TCCR0A = 0; // Normal mode
TCCR0B = (1 << CS00); // No prescaler
TIMSK |= (1 << TOIE0); // Enable overflow interrupt
// Enable global interrupts
sei();
}
ISR(TIMER0_OVF_vect) {
// Toggle PB0 (LED or other output)
PORTB ^= (1 << PB0);
}
int main() {
setup();
while (1) {
// The ISR handles the toggling
}
}
5. How it Works:
- Timer Setup: The ATtiny85's timer overflows every 32,768 clock cycles from the 32.768 kHz crystal, generating an interrupt once per second.
- Pulse Output: Each time the timer overflows, an interrupt service routine (ISR) toggles the output pin (PB0) to generate a pulse. This pulse can drive an LED or any other device.
6. Testing:
- Once the ATtiny85 is programmed and connected, you should see a 1 Hz pulse on the output pin (PB0), and if you connect an LED, it will blink once per second.
Additional Ideas:
- Power Consumption: Since the ATtiny85 is very power-efficient, this setup can be used for low-power applications, such as timekeeping or low-power sensors.
- Extended Functionality: You can expand this project to work as a simple real-time clock or timer by adding a display, such as a 7-segment display or a small LCD.
Let me know if you need more details or specific help with the code or circuit!