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资源说明：Arduino/Avr compatible libraries to control timers
# 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.
1. Divide CPU clock by selected prescaler:
16000000 / 64 = 250000 Hz
2. Get timer period:
1 / 250000 = 4 us
3. Divide your desired period by timer period, for example 20 milliseconds:
20000 us / 4 us = 5000 ticks
4. Use timer1, as timer0 and timer2 can't support more than 256 ticks:
timer1(TIMER1_PRESCALER_64, 5000U, do_something);
5. Enable global interrupts:
sei();
## Sample Code
- Using `wait*` functions:
#include
#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
#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
1. Download the source code by using the Download Button on this page
2. Rename and install the library as: `{arduino_path}/libraries/AtmegaTimers`
3. 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:
- atmega48, 88, 168, 328
- atmega164, 324, 644, 1284
- atmega640, 1280, 1281, 2560, 2561
- atmega325, 645
- ...
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