Question

我有用于调试的LPC1769 LPCXpresso和LPC-Link 2。我的开发环境是IAR。

我想使用Timer体验一个简单的LED闪烁。网上有很多示例代码。因此，我选择了为MCB1700板制作的样品之一。我还在这里和那里阅读了一些定时器如何与LPC一起工作的信息。

代码已编译，我将程序下载到了设备（LPC1769）。我以为当计时器在给定间隔内调用处理程序时，LED应该闪烁。

但是，该程序根本不会命中TIMER0_IRQHandler。

这是我main.c文件中的完整代码：

#include <lpc17xx.h>

void TIMER0_IRQHandler(void);

int main(void) 
{
  // (1) Timer 0 configuration (see page 490 of user manual)
  LPC_SC->PCONP |= 1 << 1; // Power up Timer 0 (see page 63 of user manual)
  LPC_SC->PCLKSEL0 |= 1 << 2; // Clock for timer = CCLK, i.e., CPU Clock (page 56 user manual)
  // MR0 is "Match Register 0". MR0 can be enabled through the MCR to reset
  // the Timer/Counter (TC), stop both the TC and PC, and/or generate an interrupt
  // every time MR0 matches the TC. (see page 492 and 496 of user manual)

  LPC_TIM0->MR0 = 500; //Toggle Time in mS
  //LPC_TIM0->MR0 = 1 << 23; // Give a value suitable for the LED blinking

  // frequency based on the clock frequency
  // MCR is "Match Control Register". The MCR is used to control if an
  // interrupt is generated and if the TC is reset when a Match occurs.
  // (see page 492 and 496 of user manual)
  LPC_TIM0->MCR |= 1 << 0; // Interrupt on Match 0 compare
  LPC_TIM0->MCR |= 1 << 1; // Reset timer on Match 0
  // TCR is "Timer Control Register". The TCR is used to control the Timer
  // Counter functions. The Timer Counter can be disabled or reset
  // through the TCR. (see page 492 and 494 of user manual)
  LPC_TIM0->TCR |= 1 << 1; // Manually Reset Timer 0 (forced);
  LPC_TIM0->TCR &= ~(1 << 1); // Stop resetting the timer
  // (2) Enable timer interrupt;
  // TIMER0_IRQn is 1, see lpc17xx.h and page 73 of user manual
  NVIC_EnableIRQ(TIMER0_IRQn); // see core_cm3.h header file
  // (3) Some more one-time set-up's;
  LPC_TIM0->TCR |= 1 << 0; // Start timer (see page 492 and 494 of user manual)
  LPC_SC->PCONP |= ( 1 << 15 ); // Power up GPIO (see lab1)
  LPC_GPIO1->FIODIR |= 1 << 29; // Put P1.29 into output mode. LED is connected to P1.29
  // (4) infinite loop;
  while (1) // Why do we need this?
  {
    //LPC_GPIO1->FIOPIN ^= 1 << 29; // Toggle the LED (see lab1)
  }
  return 0;
}


// Here, we describe what should be done when the interrupt on Timer 0 is handled;
// We do that by writing this function, whose address is “recorded” in the vector table
// from file startup_LPC17xx.s under the name TIMER0_IRQHandler;
void TIMER0_IRQHandler(void)
{
  // IR is "Interrupt Register". The IR can be written to clear interrupts. The IR
  // can be read to identify which of eight possible interrupt sources are
  // pending. (see page 492 and 493 of user manual)
  if ( (LPC_TIM0->IR & 0x01) == 0x01 ) // if MR0 interrupt (this is a sanity check);
  {
    LPC_TIM0->IR |= 1 << 0; // Clear MR0 interrupt flag (see page 492 and 493 of user manual)
    LPC_GPIO1->FIOPIN ^= 1 << 29; // Toggle the LED (see lab1)
  }
}

任何指针将不胜感激。

Answer 1

我运行了您的代码，我可以告诉您TIMER0_IRQHandler确实在执行，至少对我而言。为了证明这一点，请尝试运行IAR IDE调试器并在以下行中设置“断点”：

void TIMER0_IRQHandler(void)

程序每次进入时都会在此函数调用处暂停。

我对lpc1769的较低级别的函数调用没有太多的经验，但是我可以看到您的代码中的问题出在这里：

LPC_TIM0->MR0 = 500; //Toggle Time in mS
//LPC_TIM0->MR0 = 1 << 23; // Give a value suitable for the LED blinking

匹配寄存器MR0没有预分频值，因此不是每500毫秒执行一次，而是每500微秒执行一次。这类似于创建PWM信号，该信号将使LED闪烁得如此之快，以至于肉眼看不见。您可以尝试学习更多有关使用LPC_TIM0-> PR设置预分频值以使计时器/计数器的值大于1uS的信息。不使用预分频器，我可以通过设置以下内容来每1秒闪烁一次LED：

LPC_TIM0->MR0 = 100000000;

还要确保您的LED电路中有一个电阻，所以不要炸它。确保将已设置的输出引脚P1.29连接到板上的正确位置（PAD 12？）： LPC Xpresso Pinout

希望这会有所帮助！

使用LPC1769 LPCXpresso，

1 个答案: