[参考译文] TMS570LS1227：ECAP PWM 捕捉不适用于低频信号

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https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1321161/tms570ls1227-ecap-pwm-capturing-does-not-work-for-low-frequency-signals

器件型号：TMS570LS1224PGE

您好！

我们目前遇到的问题与本主题中所述的完全相同：

https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/660516/tms570ls1227-configuring-ecap-module-to-capture-lower-frequencies

不幸的是，除了"它应该以这种方式工作"之外，没有提供任何解决办法。

我们使用"example_etpwm_ecap"示例成功设置 ECAP 读数。即使占空比或周期发生轻微变化、它也能正常运行。

但是、我们需要采集67Hz、3.3V 的 PWM、占空比约为10-20%、与示例中生成的 PWM 相比、这非常慢。理论上、应该可以在计数器溢出之前捕获周期长度高达53秒的信号。

当尝试读取我们的慢速信号时、所有 ECAP 计数器都显示相同的值、因此我们只将占空比和周期值设置为零。看起来所有捕捉事件都同时发生、并且同时触发上升沿和下降沿。

我们已经通过不同的来源生成了所需的信号(以及类似的信号)、以确保我们的信号源不是问题所在。示波器中的信号看起来很好。

为什么该示例不适用于低频信号？读取相对较慢的信号需要做些什么？

此致

克里斯蒂安

/** @example example_etpwm_ecap.c
*   This is an example which describes the steps to configure ETPWM for generating PWM signal
*   and ECAP to capture the same and calculate its frequency and duty cycle,Here ETPWM1A pin is configured
*   to generate a PWM wave and is fed to ECAP1 pin.
*
*
*   @b Step @b 1:
*
*   Create a new project.
*
*   Navigate: -> File -> New -> Project
*
*   @image html example_createProject.jpg "Figure: Create a new Project"
*
*   @b Step @b 2:
*
*   Configure driver code generation:
*   - Enable ETPWM and ECAP drivers
*   - Disable others
*
*   Navigate: -> TMS570LS12x/RM46 -> Enable Drivers
*
*   @b Step @b 3:
*
*   Configure PINMUX to enable ETPWM1A and ECAP1 pins (or enable ETPWM and ECAP checkboxes)
*
*   Navigate: -> PINMUX -> Pin Muxing
*
*   Enable TBCLK sync
*
*   Navigate: -> PINMUX -> Special Pin Muxing
*
*   @b Step @b 4:
*
*   Enable ECAP1 Interrupt in VIM (Channel 104)
*
*   Navigate: -> TMS570LS12x/RM46 -> VIM Channel 96-127
*
*   @b Step @b 4:
*
*   Configure EPWM1A with specified duty and period
*
*   @image html etpwm_module_enable.jpg "Figure: Enable ETPWM modules"
*   @image html etpwm_config.jpg "Figure: EPWM1A configuration"
*
*   @b Step @b 5:
*
*   Configure ECAP1 as follows
*
*   @image html ecap_module_enable.jpg "Figure: Enable ETPWM modules"
*   @image html ecap_config.jpg "Figure: EPWM1A configuration"
*
*   @b Step @b 6:
*
*   Connect the pin ETPWM1A and ECAP1:
*
*
*   @b Step @b 7:
*
*   Copy the source code below into your sys_main.c or replace sys_main.c with this file.
*
*   The example file can also be found in the examples folder: ../HALCoGen/examples
*
*   @note HALCoGen generates an empty main function in sys_main.c,
*
*
*/

/* 
* Copyright (C) 2009-2015 Texas Instruments Incorporated - www.ti.com
* 
* 
*  Redistribution and use in source and binary forms, with or without 
*  modification, are permitted provided that the following conditions 
*  are met:
*
*    Redistributions of source code must retain the above copyright 
*    notice, this list of conditions and the following disclaimer.
*
*    Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the 
*    documentation and/or other materials provided with the   
*    distribution.
*
*    Neither the name of Texas Instruments Incorporated nor the names of
*    its contributors may be used to endorse or promote products derived
*    from this software without specific prior written permission.
*
*  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
*  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
*  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
*  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
*  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
*  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES INCLUDING, BUT NOT 
*  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
*  DATA, OR PROFITS; OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY
*  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
*  INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE 
*  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/

/* USER CODE BEGIN (0) */
/* USER CODE END */

/* Include Files */

#include "sys_common.h"

/* USER CODE BEGIN (1) */
#include "stdio.h"
#include "system.h"
#include "etpwm.h"
#include "ecap.h"
/* USER CODE END */


/** @fn void main(void)
*   @brief Application main function
*
*/

/* USER CODE BEGIN (2) */
/* USER CODE END */


void main(void)
{
/* USER CODE BEGIN (3) */

	_enable_interrupt_();
	
#if 1
	/* Initialise EPWM and ECAP with GUI configuration */ 
	etpwmInit();
	ecapInit();
#else
	/* Alternate code for configuring ETPWM and ECAP */
		/* Configure ETPWM1 */
	/* Set the TBCLK frequency =  VCLK4 frequency = 90MHz */
	etpwmSetClkDiv(etpwmREG1, ClkDiv_by_1, HspClkDiv_by_1);

	/* Set the time period as 1000 ns (Divider value = (1000ns * 90MHz) - 1 = 89)*/
	etpwmSetTimebasePeriod(etpwmREG1, 89);

	/* Configure Compare A value as half the time period */
	etpwmSetCmpA(etpwmREG1, 45);

	/* Configure mthe module to set PWMA value as 1 when CTR=0 and as 0 when CTR=CmpA  */
	etpwmActionQualConfig_t configPWMA;
	configPWMA.CtrEqZero_Action = ActionQual_Set;
	configPWMA.CtrEqCmpAUp_Action = ActionQual_Clear;
	configPWMA.CtrEqPeriod_Action = ActionQual_Disabled;
	configPWMA.CtrEqCmpADown_Action = ActionQual_Disabled;
	configPWMA.CtrEqCmpBUp_Action = ActionQual_Disabled;
	configPWMA.CtrEqCmpBDown_Action = ActionQual_Disabled;
	etpwmSetActionQualPwmA(etpwmREG1, configPWMA);

	/* Start counter in CountUp mode */
	etpwmSetCount(etpwmREG1, 0);
	etpwmSetCounterMode(etpwmREG1, CounterMode_Up);
	etpwmStartTBCLK();

	/* Configure ECAP1 */
	/* Configure Event 1 to Capture the rising edge */
	ecapSetCaptureEvent1(ecapREG1, RISING_EDGE, RESET_DISABLE);

	/* Configure Event 2 to Capture the falling edge */
	ecapSetCaptureEvent2(ecapREG1, FALLING_EDGE, RESET_DISABLE);

	/* Configure Event 3 to Capture the rising edge with reset counter enable */
	ecapSetCaptureEvent3(ecapREG1, RISING_EDGE, RESET_ENABLE);

	/* Set Capure mode as Continuous and Wrap event as CAP3  */
	ecapSetCaptureMode(ecapREG1, CONTINUOUS, CAPTURE_EVENT3);

	/* Start counter */
	ecapStartCounter(ecapREG1);

	/* Enable Loading on Capture */
	ecapEnableCapture(ecapREG1);

	/* Enable Interrupt for CAP3 event */
	ecapEnableInterrupt(ecapREG1, ecapInt_CEVT3);
	
#endif
    /*  ... run forever  */
    while(1);
	
/* USER CODE END */	
}

/* USER CODE BEGIN (4) */
void ecapNotification(ecapBASE_t *ecap,uint16 flags)
{
	uint32 cap1, cap2, cap3;
	float64 duty, period;

	cap1 = ecapGetCAP1(ecapREG1);
	cap2 = ecapGetCAP2(ecapREG1);
	cap3 = ecapGetCAP3(ecapREG1);

	duty = (cap2 - cap1)*1000/VCLK4_FREQ;
	period = (cap3 - cap1)*1000/VCLK4_FREQ;

	printf("Duty = %fns\n", duty);
	printf("Period = %fns\n\n", period);

}
/* USER CODE END */

1 年多前