atmega-timers

atmega-timers is an Arduino/Avr compatible library to control timers 0, 1 and 2.

Description

This library contains several functions to use the timers in different ways.

One way is using the timers to execute a function on a defined period, indefinitely.
```
  void timer0(uint8_t prescaler, uint8_t ticks, void (*f)())
  void timer1(uint8_t prescaler, uint16_t ticks, void (*f)())
  void timer2(uint8_t prescaler, uint8_t ticks, void (*f)())

  void timer0_stop()
  void timer1_stop()
  void timer2_stop()
```
- prescaler are predefined constants in the header file. For example:
```
  TIMER0_PRESCALER_8
  TIMER0_PRESCALER_64
  ...
```
- ticks are the number of steps the timer will count. Current limits are:
```
  timer0: 0 - 255
  timer1: 0 - 65535
  timer2: 0 - 255
```
- f is the function to execute after all ticks are consumed. Must be declared void with no parameters:
```
  void sample() {
  	...
  }
```
- timerX_stop() disables that timer by setting prescaler to "none". Energy saving feature.
- You can disable interrupt definition if you want to use that timer for your own purposes. Just comment or delete one of those lines inside atmega-timers.h file:
```
  #define ENABLE_TIMER0
  #define ENABLE_TIMER1
  #define ENABLE_TIMER2
```

Other way is implementing the traditional delay routine. The function will block-wait until the count is done.

  void wait0(uint8_t prescaler, uint8_t ticks)
  void wait1(uint8_t prescaler, uint16_t ticks)
  void wait2(uint8_t prescaler, uint8_t ticks)

prescaler are predefined constants in the header file. For example:
```
  TIMER0_PRESCALER_8
  TIMER0_PRESCALER_64
  ...
```
ticks are the number of steps the timer will count. Current limits are:
```
  timer0: 0 - 255
  timer1: 0 - 65535
  timer2: 0 - 255
```

Usage

You need to know your CPU clock frequency before setting the timers.

Divide CPU clock by selected prescaler:
```
 16000000 / 64 = 250000 Hz
```
Get timer period:
```
 1 / 250000 = 4 us
```
Divide your desired period by timer period, for example 20 milliseconds:
```
 20000 us / 4 us = 5000 ticks
```
Use timer1, as timer0 and timer2 can't support more than 256 ticks:
```
 timer1(TIMER1_PRESCALER_64, 5000U, do_something);
```
Enable global interrupts:
```
 sei();
```

Sample Code

Using wait* functions:

  #include <avr/io.h>
  #include "atmega-timers.h"

  // toggle PORTB status
  void toggle() {
  	static uint8_t output = 0xff;

  	PORTB = output;
  	output = !output;
  }

  void main() {
  	// set all pins of PORTB as output
  	DDRB = 0xff;
  	
  	// toggle PORTB every 500ms (using 16Mhz clock)
  	while(1) {
  		toggle();
  		wait1(TIMER1_PRESCALER_1024, 7812U);
  	}
  }

Using timer* functions:

  #include <avr/io.h>
  #include "atmega-timers.h"

  // toggle PORTB status
  void toggle() {
  	static uint8_t output = 0xff;

  	PORTB = output;
  	output = !output;
  }

  void main() {
  	// set all pins of PORTB as output
  	DDRB = 0xff;
  	
  	// toggle PORTB every 500ms (using 16Mhz clock)
  	timer1(TIMER1_PRESCALER_1024, 7812U, toggle);
  	
  	// enable global interrupts
  	sei();

  	while(1) {
  		// your code goes here
  	}
  }

Both examples have the same result.

Running it in Arduino

Download the source code by using the Download Button on this page
Rename and install the library as: {arduino_path}/libraries/AtmegaTimers
Open Arduino and go to "Import Library" option. Choose AtmegaTimers from menu.

Atmel Model Support

It should work with a long range of devices, for example: