【MCXA156开发板测评】-3-LPTMR体验

慕容雪花

【MCXA156开发板测评】-3-LPTMR体验 [复制链接]

MCXA156片上定时器外设可谓是非常丰富，有Standart Counter/Timers 即CTimer， 还有Windowed Watchdog Timer，Micro-Tick Timer， OS Event Timer，Wake Timer。

在NXP的论坛上，也找到了一些对不同种类的NXP片上定时器的介绍：链接

1)SCTimer/PWM: can generate complicated PWM signal to control even motor, have capture function, can generate interrupt with programmable interval, can be a frequency divider.

2)CTimer: can generate simple PWM signal, can generate interrupt with programmable interval, has capture function, can be a frequency divider.

3)Multi-Rate Timer (MRT): can only generate interrupt

4)Repetitive Interrupt Timer (RIT): can only generate interrupt

5)System tick timer (SYSTICK): can generate interrupt for core

6)Micro-tick Timer (UTICK): can generate interrupt, and have capture function

 

本次体验一下使用NXP的工具全家桶MCUXPRESSO IDE配合内置的MCU CONFIG TOOL来快速制作一个1ms时基的中断服务程序，来闪烁小灯，串口输出。

首先点击使能LPTMR的时钟：

 

 

点击IDE右上角的USB符号，进入到外设配置界面。

 

之后可以输入LPTMR0进行搜索，添加该模块后，进入到配置界面，比如运行模式，频率，是否开启中断，是否要在初始化函数中启动LPTMR0等。

区别于别的IDE，在MCU ConfigTool里面还提供了ISR模板，可以点击“Copy to clipboard”来复制然后粘贴到自己对应用代码中。

如下所示即为添加了闪烁小灯与串口打印后的ISR。

/* LPTMR0_IRQn interrupt handler */
void LPTMR0_IRQHANDLER(void) {
  uint32_t intStatus;
  /* Reading all interrupt flags of status register */
  intStatus = LPTMR_GetStatusFlags(LPTMR0_PERIPHERAL);
  LPTMR_ClearStatusFlags(LPTMR0_PERIPHERAL, intStatus);

  /* Place your code here */
	static uint32_t cnt = 0;
	cnt++;
	if(cnt%1000 == 0){
  /* Toggle pin connected to LED */
  GPIO_PortToggle(GPIO3, 1u << 0);
  PRINTF("\r\n GPIO3_0 RED LED TOOGLED, cnt = %d", cnt);
	}
  /* Add for ARM errata 838869, affects Cortex-M4, Cortex-M4F
     Store immediate overlapping exception return operation might vector to incorrect interrupt. */
  #if defined __CORTEX_M && (__CORTEX_M == 4U)
    __DSB();
  #endif
}

下面是IDE自动生成的LPTMR0的配置及初始化代码：

const lptmr_config_t LPTMR0_config = {
  .timerMode = kLPTMR_TimerModeTimeCounter,
  .pinSelect = kLPTMR_PinSelectInput_0,
  .pinPolarity = kLPTMR_PinPolarityActiveHigh,
  .enableFreeRunning = false,
  .bypassPrescaler = true,
  .prescalerClockSource = kLPTMR_PrescalerClock_3,
  .value = kLPTMR_Prescale_Glitch_0
};

static void LPTMR0_init(void) {
  /* Initialize the LPTMR */
  LPTMR_Init(LPTMR0_PERIPHERAL, &LPTMR0_config);
  /* Set LPTMR period */
  LPTMR_SetTimerPeriod(LPTMR0_PERIPHERAL, LPTMR0_TICKS);
  /* Configure timer interrupt */
  LPTMR_EnableInterrupts(LPTMR0_PERIPHERAL, kLPTMR_TimerInterruptEnable);
  /* Interrupt vector LPTMR0_IRQn priority settings in the NVIC. */
  NVIC_SetPriority(LPTMR0_IRQN, LPTMR0_IRQ_PRIORITY);
  /* Enable interrupt LPTMR0_IRQN request in the NVIC */
  EnableIRQ(LPTMR0_IRQN);
  /* Start the LPTMR timer */
  LPTMR_StartTimer(LPTMR0_PERIPHERAL);
}

烧录，全速运行，看到串口大概1s输出一次。

 

换个带时间戳的串口助手，看的更细节：

 

Jacktang

添加该模块后，进入到配置界面，然后的操作好像有点麻烦了