LPC MicrocontrollersのトピックRe: LPC55S69 ctimer PWM

LPC55S69 ctimer PWM

wangyibin — Mon, 28 Feb 2022 05:56:53 GMT

在CTIMER_GetPwmPeriodValue（2， 20， timerClock），把占空比恒定为20%，频率依次调为100HZ 10HZ 5HZ 2HZ时都能在示波器上检测到
相关波形，并且占空比正确。在频率降为1HZ的时候，相关波形不正确，示波器上显示占空比为60%。
请问在lpc55s69中定时器2不支持产生1hz频率的pwm波形吗？

Re: LPC55S69 ctimer PWM

xiangjun_rong — Mon, 28 Feb 2022 08:41:02 GMT

Hi,

How about using the code

CTIMER_GetDefaultConfig(ctimer_config_t *config)

config->prescale=100;

BTW, can you tell us the value of the two variables if you set up 1HZ PWM

volatile uint32_t g_pwmPeriod = 0U;
volatile uint32_t g_pulsePeriod = 0U;

Hope it can help you

XiangJun Rong

Re: LPC55S69 ctimer PWM

wangyibin — Mon, 28 Feb 2022 09:40:15 GMT

预分频值为7，g_pwmPeriod=47999999 g_pulsePeriod=4800000
把预分频值改为100后能够成功的在示波器上检测到波形，g_pwmPeriod=95999999，g_pulsePeriod=500654
在CTIMER_GetPwmPeriodValue(1, 30, timerClock);中的第二参数是那个占空比，我设置为30，但用示波器检测到的为25%

Re: LPC55S69 ctimer PWM

xiangjun_rong — Tue, 01 Mar 2022 06:43:52 GMT

Hi,

I have to say when you call the follwoing code

CTIMER_GetPwmPeriodValue(20000, 20, timerClock);
CTIMER_SetupPwmPeriod(CTIMER, CTIMER_MAT_OUT, g_pwmPeriod, g_pulsePeriod, false);
//Can not use kCTIMER_Match_3, which is used to control PWM period

CTIMER_GetPwmPeriodValue(20000, 40, timerClock);
CTIMER_SetupPwmPeriod(CTIMER, kCTIMER_Match_0, g_pwmPeriod, g_pulsePeriod, false);

when you configure multiple PWM channel and use the status_t CTIMER_GetPwmPeriodValue(uint32_t pwmFreqHz, uint8_t dutyCyclePercent, uint32_t timerClock_Hz) to compute the variables g_pwmPeriod/g_pulsePeriod, the first parameter pwmFreqHz must be the same for multiple calling CTIMER_GetPwmPeriodValue(), only the duty cycle can be different. Otherwise, there is error.

Hope it can help you

XiangJun Rong