将 Atmega8 的定时器代码实现到 Atmega16答案

【问题标题】：Implementing timer code for Atmega8 into Atmega16将 Atmega8 的定时器代码实现到 Atmega16
【发布时间】：2012-12-19 22:23:32
【问题描述】：

这段代码 sn-p 是为 Atmega8 编写的，取自 clapper circuit using Atmega8。任何人都可以将此代码 sn-p 转换为 Atmega16 并稍加解释。因为我正在尝试为 Atmega16 实现相同的功能并且在计时器部分遇到了一些问题。

#define BURST_TIME  70
#define READY_TIME  150
#define TIME_OUT    300

void timer_init()
{
    TIFR |= (1<<TOV0);      
    //set interrupt on overflow
    TIMSK |= (1<<TOIE0);
    TCNT0 = 223;
}

ISR (TIMER0_OVF_vect)
{       
    TCNT0 = 223;
    timer++;

    if (timer == BURST_TIME)
    {
        burst = 1;
        ready = 0;
    } else if (timer == READY_TIME)
    {
        burst = 0;
        ready = 1;
    } else if (timer == TIME_OUT)
    {
        timer = 0;
        burst = 0;
        ready = 0;
        first = 0;
        stop_timer();
    }
}

void start_timer()
{
    TCCR0 |= (1<<CS02);
}

void stop_timer()
{
    TCCR0 &= ~(1<<CS02);
}

【问题讨论】：

标签： microcontroller code-conversion atmega winavr atmega16

【解决方案1】：

尝试使用芯片的 Atmel 数据表并比较定时器寄存器，您会找到所需的一切

Atmega8：http://www.atmel.com/images/doc2486.pdf 有用：注册摘要第 280 页

Atmega16：http://www.atmel.com/Images/doc2466.pdf 有用：注册摘要页面 331

你想使用定时器 0，那是一个 8 位定时器（Atmega16 上的第 71 页）

现在让我们试着分析一下代码

TIFR |= (1<<TOV0); // TIFR Thats the Timer/Counter0 Interrupt Flag Register
                   // TOV0: Timer/Counter0 Overflow Flag
                   // The bit TOV0 is set when an overflow occurs in Timer/Counter0.
                   // Datasheet page: 86

TIMSK |= (1<<TOIE0);  // Timer/Counter Interrupt Mask Register
                      // TOIE0: Timer/Counter0 Overflow Interrupt Enable
                      // When the TOIE0 bit is written to one, and the I-bit in the `status Register is set, the
                      // Timer/Counter0 Overflow interrupt is enabled

TCNT0 = 223; // TCNT0:  0 to 255 or 0x00 to 0xFF
             // with each clock it increases by 1
             // when the register hits 255, a Timer-Overflow is triggerd (ISR...)
             // The flag can be queried or used to trigger an interrupt.
             // Datasheet Page 85

TCCR0 |= (1<<CS02); // TCCR0: Timer/Counter Control Register
                    // CS02: Bit 2:0 – CS02:0: Clock Select
                    // This means that your running the Timer with a                               
                    // Prescaler of 256 (CPU frequency / 256)
                    // This line starts the Timer!
                    // Datasheet Page: 85

ISR (TIMER0_OVF_vect) // will be executed when a overflow is triggerd
{ 
    // Do something
    // Keep the execution time short in this section
}

【讨论】：