1.4 PWM操作
1.4.6 PWM定时器启动步骤
CRLRx
Set by H/W
Clear by S/W
CAPIFx
5. 根据PWM周期设置PWM计数器(CNR) 6. 设置中断使能寄存器(PIER)
7. 设置PWM输出使能(POE) 8. 设置相应的GPIO口为PWM功能 9. 使能PWM定时器(PCR)
1.4.7 PWM停止流程 方式1:
设定16位向下计数计数器(CNR)为0 ，并查看PDR状态，当PDR达到0 ，关闭PWM定时器 (PCR的 CHxEN位). (推荐)
方式2:
设定16位向下计数计数器(CNR)为0，当中断发生，在中断内关闭PWM定时器(PCR的CHxEN位). (推荐) 方式3:
直接关闭PWM定时器(PCR的CHxEN位). (不推荐)
1.4.8 捕捉启动流程
1. 设置时钟选择（CSR）
2. 设置预分频(PPR)
3. 设置通道使能，上升/下降沿中断使能及输入信号反向开/关(CCR0, CCR1) 4. 设置PWM计数器(CNR)
5. 设置捕捉输入使能寄存器(CAPENR) 6. 设置相应GPIO口为PWM功能 7. 使能PWM定时器(PCR)
2 代码部分
2.1
主函数(在Smpl_DrvPWM.c中)
下面的代码代表PWM定时器的两个主要功能：PWM功能和捕捉功能。首先是7个特定的频率波形从 PWM0输入蜂鸣器，接下来PWM3作为捕捉操作，捕捉PWM1输出的波形特性，并计算PWM1输出的低 脉冲宽度，高脉冲宽度及周期
int32_t main (void) {
S_DRVPWM_TIME_DATA_T sPt;
STR_UART_T sParam;
uint8_t u8Item;
uint8_t u8Timer, u8CapTimer;
int32_t i32Loop = 1;
int32_t i32TestLoop = 1;
/*---Deleted---*/
/* Enable PWM clock */
DrvPWM_Open();
/* Set PWM pins */
DrvGPIO_InitFunction(FUNC_PWM01);
DrvGPIO_InitFunction(FUNC_PWM23);
DrvGPIO_InitFunction(FUNC_PWM45);
DrvGPIO_InitFunction(FUNC_PWM67);
UNLOCKREG();
DrvSYS_SetHCLKSource(0);
LOCKREG();
/*---Deleted---*/
/* PWM Timer property */
sPt.u8Mode = DRVPWM_TOGGLE_MODE;
sPt.u32Frequency = g_u16Frequency;
sPt.u8HighPulseRatio = 1; /* High Pulse peroid : Total Pulse peroid = 1 : 100 */
sPt.i32Inverter = 0;
u8Timer = DRVPWM_TIMER0;
/* Select PWM engine clock */
DrvPWM_SelectClockSource(u8Timer, DRVPWM_HCLK);
/* Set PWM Timer0 Configuration */
DrvPWM_SetTimerClk(u8Timer, &sPt);
/* Enable Output for PWM Timer0 */
DrvPWM_SetTimerIO(u8Timer, 1);
/* Enable Interrupt Sources of PWM Timer0 and install call back function */
DrvPWM_EnableInt(u8Timer, 0, DRVPWM_PwmIRQHandler);
/* Enable the PWM Timer 0 */
DrvPWM_Enable(u8Timer, 1);
while (g_u8PWMCount);
/*---*/
/* Stop PWM Timer0 (Recommended procedure method 2) */
/* Set PWM Timer counter as 0, When interrupt request happen,
disable PWM Timer */
/* Set PWM Timer counter as 0 in Call back function */
/*---*/
/* Disable the PWM Timer 0 */
DrvPWM_Enable(u8Timer, 0);
printf("PWM Capture Test\n");
printf("Use PWM Capture 3 to capture the PWM Timer1 Waveform\n");
/*---*/
/* Set the PWM Timer1 as output function. */
/*---*/
/* PWM Timer property for Output waveform */
sPt.u8Mode = DRVPWM_TOGGLE_MODE;
sPt.u32Frequency = 250; /* 250 Hz */
sPt.u8HighPulseRatio = 30; /* High Pulse peroid : Total Pulse peroid = 30 : 100 */
sPt.i32Inverter = 0;
u8Timer = DRVPWM_TIMER1;
/* Select PWM01 engine clock */
DrvPWM_SelectClockSource(u8Timer, DRVPWM_HCLK);
/* Set PWM Timer1 Configuration */
DrvPWM_SetTimerClk(u8Timer, &sPt);
/* Enable Output for PWM Timer1 */
DrvPWM_SetTimerIO(u8Timer, 1);
/* Enable the PWM Timer1 */
DrvPWM_Enable(u8Timer, 1);
/*---*/
/* Set the PWM Capture 3 for capture function */
/*---*/
/* PWM Timer property for Capture */
sPt.u8Mode = DRVPWM_TOGGLE_MODE;
sPt.u32Frequency = 100; /* Set the proper frequency to capture data (Less than the input data)*/
sPt.u8HighPulseRatio = 50; /* High Pulse peroid : Total Pulse peroid = 50 : 100 (Set a non-zero value) */
sPt.u32Duty = 0x10000; /* Set the counter to the maximum value */
sPt.i32Inverter = 0;
u8CapTimer = DRVPWM_CAP3;
/* Select PWM engine clock */
DrvPWM_SelectClockSource(u8CapTimer, DRVPWM_HCLK);
/* Set PWM Timer 3 for Capture */
DrvPWM_SetTimerClk(u8CapTimer, &sPt);
/* Enable Interrupt Sources of PWM Capture3 */
DrvPWM_EnableInt(u8CapTimer, DRVPWM_CAP_FALLING_INT, NULL);
/* Enable Input function for PWM Capture 3 */
DrvPWM_SetTimerIO(u8CapTimer, 1);
/* Enable the PWM Capture3 */
DrvPWM_Enable(u8CapTimer, 1);
/* Capture the Input Waveform Data */
CalPeriodTime(u8CapTimer);
/*---*/
/* Stop PWM Timer 1 (Recommended procedure method 1) */
/* Set PWM Timer counter as 0, When PWM internal counter reaches
to 0, disable PWM Timer*/
/*---*/
/* Set PWM Timer 1 counter as 0 */
DrvPWM_SetTimerCounter(u8Timer, 0);
/* Wait PWM Timer1 Interrupt */
while (DrvPWM_GetTimerCounter(u8Timer));
/* Disable PWM Timer 1 */
DrvPWM_Enable(u8Timer, 0);
/* Disable Output function for PWM Timer 1 */
DrvPWM_SetTimerIO(u8Timer, 0);
/*---*/
/* Stop PWM Timer 3 (Recommended procedure method 1) */
/* Set PWM Timer counter as 0, When PWM internal counter reaches
to 0, disable PWM Timer*/
/*---*/
/* Set PWM Capture 3 counter as 0 */
DrvPWM_SetTimerCounter(u8CapTimer & 0x0F, 0);
/* Wait PWM Capture 3 Counter reach to 0 */
while (DrvPWM_GetTimerCounter(u8CapTimer));
/* Clear the PWM Capture 3 Interrupt */
DrvPWM_ClearInt(u8CapTimer);
/* Disable PWM Capture 3 */
DrvPWM_Enable(u8CapTimer, 0);
/* Disable Input function for PWM Capture 3 */
DrvPWM_SetTimerIO(u8CapTimer, 0);
/*---Deleted---*/
printf("PWM sample is complete.\n");
DrvPWM_Close();
return 0;
}
2.2 PWM回调函数
回调函数用来计算PWM脉冲，当脉冲计数器达到一个特定值时，回调函数将设置CNR为0并清除停止定 时器的标志。
/*---*/
/* PWM Timer Callback function */
/*---*/
void DRVPWM_PwmIRQHandler() {
if (s_u32Pulse == 1 * g_u16Frequency /10) {
/*---*/
/* Stop PWM Timer 0 (Recommended procedure method 2) */
/* Set PWM Timer counter as 0, When interrupt request happen,
disable PWM Timer */
/*---*/
DrvPWM_SetTimerCounter(DRVPWM_TIMER0, 0);
}
if (s_u32Pulse == 1 * g_u16Frequency /10 + 1) g_u8PWMCount = 0;
s_u32Pulse++;
}
2.3
捕捉功能
捕捉功能用来计算输入波形的信息
注意：当下降或上升沿中断使能时，CAPIFx, x=0~7 位被硬件置位，软件可以通过对该位写1清零，如 果此位没有清零，PWM计数器将不会在下一个捕捉中断发生时重载。
void CalPeriodTime(uint8_t u8Capture) {
uint16_t u32Count[4];
uint32_t u32i;
uint16_t u16RisingTime, u16FallingTime, u16HighPeroid, u16LowPeroid, u16TotalPeroid;
/* Clear the Capture Interrupt Flag (Time A) */
DrvPWM_ClearCaptureIntStatus(u8Capture, DRVPWM_CAP_FALLING_FLAG);
/* Wait for Interrupt Flag (Falling) */
while (DrvPWM_GetCaptureIntStatus(u8Capture, DRVPWM_CAP_FALLING_FLAG) != 1);
/* Clear the Capture Interrupt Flag (Time B)*/
DrvPWM_ClearCaptureIntStatus(u8Capture, DRVPWM_CAP_FALLING_FLAG);
u32i = 0;
while (u32i < 4) {
/* Wait for Interrupt Flag (Falling) */
while(DrvPWM_GetCaptureIntStatus(u8Capture, DRVPWM_CAP_FALLING_FLAG) != 1);
/* Clear the Capture Interrupt Flag */
DrvPWM_ClearCaptureIntStatus(u8Capture, DRVPWM_CAP_FALLING_FLAG);
/* Clear the Capture Rising Interrupt Flag */
DrvPWM_ClearCaptureIntStatus(u8Capture, DRVPWM_CAP_RISING_FLAG);
/* Get the Falling Counter Data */
u32Count[u32i++] = DrvPWM_GetFallingCounter(u8Capture);
/* Wait for Capture Rising Interrupt Flag */
while(DrvPWM_GetCaptureIntStatus(u8Capture, DRVPWM_CAP_RISING_FLAG) != 1);
/* Clear the Capture Rising Interrupt Flag */
DrvPWM_ClearCaptureIntStatus(u8Capture, DRVPWM_CAP_RISING_FLAG);
/* Get the Rising Counter Data */
u32Count[u32i++] = DrvPWM_GetRisingCounter(u8Capture);
}
u16RisingTime = u32Count[1];
u16FallingTime = u32Count[0];
u16HighPeroid = u32Count[1] - u32Count[2];
u16LowPeroid = 0x10000 - u32Count[1];
u16TotalPeroid = 0x10000 - u32Count[2];
printf("Test Result:\nRising Time = %d, Falling Time = %d.\nHigh Period =
%d, Low Period = %d, Total Period = %d.\n\n",
u16RisingTime, u16FallingTime, u16HighPeroid, u16LowPeroid, u16TotalPeroid);
}
2.4 API使用参考
• PWM Driver Reference Guide.doc
3 运行环境设置及结果
3.1
测试Smpl_DrvPWM
PWM示例程序，Smpl_DrvPWM,可以通过Keil MDK工具编译并通过ICE下载到NUC1xx系列DEV板，用 户可以在ICE环境下执行代码或复位DEV板执行已经下载到片内Flash的程序，然后根据提示选择测试 项，PWM波形测试和PWM捕捉测试
3.2 PWM波形测试结果
蜂鸣器中可以听到不同音符的频率(Do, Re, Mi, Fa, Sol, La, 和Si)，或者用示波器测试GPIO A12的波 形，频率和占空比将与选择的音调一致
3.3 PWM捕捉测试结果
PWM3用来测试PWM1输出波形特性，首先将GPIO A13 (PWM1功能脚)与GPIO A15 (PWM3功能脚)连 接，PWM3将在上升/下降沿时获得计数器的值，根据这些值计算出波形特性：周期，占空比等等
4 修订历史
版本 日期 描述
0.01 2010，3 初次发布
Important Notice
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Please note that all data and specifications are subject to change without notice. All the trademarks of products and companies mentioned in this datasheet belong to their respective owners.