使用DMA的方式來捕獲輸入波形中一個周期內的高低電平的持續(xù)時間，從而計算出輸入頻率；

捕獲分辨率在這里設置到了1us；

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/***************************************************************************** * * File Name : main.c * * Description: main * * Copyright (c) 2014 Winner Micro Electronic Design Co., Ltd. * All rights reserved. * * Author : dave * * Date : 2014-6-14 *****************************************************************************/ #include "wm_include.h" #include "wm_type_def.h" #include "FreeRTOS.h" #include "task.h" #include "wm_gpio.h" #include "wm_pwm.h" #include "wm_cpu.h" #include "wm_dma.h" #include "wm_gpio_afsel.h" #include "wm_timer.h"#define COUNTER_FREQ 1000000 #define ZERO_DETEC_IO WM_IO_PB_18 #define PWM_CAP_CHANNEL 0typedef struct _frequency_info {volatile u32 pwmDmaCap;volatile u32 period_ticks;volatile u32 frequecy; } frequency_info;static frequency_info f_info;static void pwm_dma_callback(void *arg) {//printf("pwmH:%d, pwmL:%d\n", (f_info.pwmDmaCap >> 16), (f_info.pwmDmaCap & 0x0000ffff));f_info.period_ticks = (f_info.pwmDmaCap >> 16) + (f_info.pwmDmaCap & 0x0000ffff); }static int pwm_capture_mode_dma(u8 channel, u32 freq) {u8 dmaCh;int frequecy = 0, high, low;struct tls_dma_descriptor DmaDesc;tls_sys_clk sysclk;memset( &f_info, 0, sizeof(f_info) );tls_sys_clk_get(&sysclk);wm_pwm1_config(ZERO_DETEC_IO);tls_pwm_stop(channel);dmaCh = tls_dma_request(1, TLS_DMA_FLAGS_CHANNEL_SEL(TLS_DMA_SEL_PWM_CAP0) | TLS_DMA_FLAGS_HARD_MODE);DmaDesc.src_addr = HR_PWM_CAPDAT;DmaDesc.dest_addr = (unsigned int)&(f_info.pwmDmaCap);DmaDesc.dma_ctrl = TLS_DMA_DESC_CTRL_DEST_ADD_INC | TLS_DMA_DESC_CTRL_BURST_SIZE1 | TLS_DMA_DESC_CTRL_DATA_SIZE_WORD | TLS_DMA_DESC_CTRL_TOTAL_BYTES(400);DmaDesc.valid = TLS_DMA_DESC_VALID;DmaDesc.next = NULL;tls_dma_start(dmaCh, &DmaDesc, 0);tls_dma_irq_register(dmaCh, pwm_dma_callback, NULL, TLS_DMA_IRQ_TRANSFER_DONE);tls_pwm_cap_init(channel, sysclk.apbclk * UNIT_MHZ / freq, DISABLE, WM_PWM_CAP_DMA_INT);tls_pwm_start(channel);while(f_info.period_ticks == 0);tls_pwm_stop(channel);high = f_info.period_ticks>>16;low = f_info.period_ticks&0xffff;printf("LEVEL: H:%d, L:%d\n", high, low);frequecy = COUNTER_FREQ/(high + low);printf("input freq: %dHz\n", frequecy);f_info.frequecy = frequecy;return frequecy; }static int gpio_initial(void) {tls_gpio_cfg(ZERO_DETEC_IO, WM_GPIO_DIR_INPUT, WM_GPIO_ATTR_PULLHIGH);return WM_SUCCESS; }void ctrl_task9(int *arg) {printf("application start.\n");wm_pwm2_config(WM_IO_PB_17);tls_pwm_init(1, 60, 99, 0);tls_pwm_start(1);gpio_initial();pwm_capture_mode_dma(PWM_CAP_CHANNEL, COUNTER_FREQ);while(1){ tls_os_time_delay(HZ);} }int misc_task_start(void (*func)(void *), char *task_name, u32 stack_size, void *arg, u8 uxTaskPriority) {return xTaskCreate(func, /* The function that implements the task. */task_name, /* Just a text name for the task to aid debugging. */stack_size, /* The stack size is defined in FreeRTOSIPConfig.h. */arg, /* The task parameter, not used in this case. */uxTaskPriority, /* The priority assigned to the task is defined in FreeRTOSConfig.h. */NULL); /* The task handle is not used. */}void UserMain(void) {misc_task_start(ctrl_task9, "ctr9", 256, NULL, 5); }

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