本文主要是介绍嵌入式应用之FIFO模块原理与实现,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
FIFO介绍与原理
FIFO是First-In First-Out的缩写,它是一个具有先入先出特点的缓冲区。FIFO在嵌入式应用的非常广泛,可以说有数据收发的地方,基本就有FIFO的存在。或者为了降低CPU负担,提高数据处理效率,可以在积累到一定的数据量之后,再一次性处理。在嵌入式系统中,FIFO是基于一维数组和结构体实现的循环队列(Queue),或者叫环形队列。可以分为同步FIFO或异步FIO,一般用于数据缓冲,或者不同时钟域之间的数据传递。
FIFO设计中,最重要的满和空的判断条件,需要遵循FIFO读写的两个规则:
●FIFO为空时,不能执行读操作
●FIFO为满时,不能执行写操作
FIFO 代码实现
使用一维数组来构造一个环形缓冲区,读写地址循环递增,分别实现FIFO初始化、读写操作、判断空满、获取元素个数等函数,并封装成模块。
msgfifo.h
#ifndef __MQUEUE_H__
#define __MQUEUE_H__
#include <stdio.h>
#include <stdint.h>#define FIFO_SIZE 6
#define qdata_t uint8_ttypedef enum {QUEUE_OK,QUEUE_FULL,QUEUE_EMPTY
}qstatus_t;typedef struct {uint16_t addr_wr;uint16_t addr_rd;uint16_t length;qdata_t fifo[FIFO_SIZE];
}queue_t;qstatus_t queue_reset(queue_t * q);
qstatus_t queue_read(queue_t *q, qdata_t *pdata);
qstatus_t queue_write(queue_t *q, qdata_t data);
int queue_isFull(queue_t *q);
int queue_isEmpty(queue_t *q);
int queue_print(queue_t *q);#endif
msgfifo.c
#include "msgfifo.h"qstatus_t queue_reset(queue_t * q) {int i = 0;q->addr_wr = 0;q->addr_rd = 0;q->length = FIFO_SIZE;for(i=0; i<q->length; i++) {q->fifo[i] = 0;}return QUEUE_OK;
}qstatus_t queue_write(queue_t *q, qdata_t data)
{if(queue_isFull(q)){printf("Write failed(%d), queue is full\n", data);return QUEUE_FULL;}q->fifo[q->addr_wr] = data;q->addr_wr = (q->addr_wr + 1) % q->length;printf("write success: %02d\n", data);queue_print(q);return QUEUE_OK;
}qstatus_t queue_read(queue_t *q, qdata_t *pdata)
{if(queue_isEmpty(q)){printf("Read failed, queue is empty\n");return QUEUE_EMPTY;}*pdata = q->fifo[q->addr_rd];q->addr_rd = (q->addr_rd + 1) % q->length;printf("read success: %02d\n", *pdata);queue_print(q);return QUEUE_OK;
}int queue_isEmpty(queue_t *q)
{return (q->addr_wr == q->addr_rd);
}int queue_isFull(queue_t *q)
{return ((q->addr_wr + 1) % q->length == q->addr_rd);
}int queue_count(queue_t *q)
{if(q->addr_rd <= q->addr_wr)return (q->addr_wr - q->addr_rd);//addr_rd > addr_wr;return (q->length + q->addr_wr - q->addr_rd);
}int queue_print(queue_t *q)
{int i = 0;int j = 0;for(i = 0; i < q->addr_rd; i++)printf(" ");printf("rd=%d", q->addr_rd);printf("\n");for(i = 0; i < q->length; i++){if(q->addr_wr > q->addr_rd){if(i >= q->addr_rd && i < q->addr_wr)printf("[%02d] ", q->fifo[i]);elseprintf("[ ] ");}else //addr_rd > addr_wr{if(i < q->addr_wr || i >= q->addr_rd)printf("[%02d] ", q->fifo[i]);elseprintf("[ ] ");}}printf("------count = %d\n", queue_count(q));for(i = 0; i < q->addr_wr; i++)printf(" ");printf("wr=%d", q->addr_wr);printf("\n");return QUEUE_OK;
}
fifotest.c
#include "msgfifo.h"int main(int argc, char * argv[]){queue_t queue;qdata_t data;qdata_t msgd[8] = {'a','b','c','d', 'e', 'f', 'g'};// queue initqueue_reset(&queue);queue_write(&queue, msgd[0]);queue_write(&queue, msgd[1]);queue_write(&queue, msgd[2]);queue_read(&queue, &data);queue_read(&queue, &data);queue_write(&queue, msgd[3]);queue_write(&queue, msgd[4]);queue_write(&queue, msgd[5]);queue_write(&queue, msgd[6]);queue_read(&queue, &data);queue_read(&queue, &data);queue_read(&queue, &data);queue_write(&queue, msgd[1]);queue_write(&queue, msgd[3]);queue_write(&queue, msgd[5]);queue_read(&queue, &data);// system("pause");return 0;
}
这篇关于嵌入式应用之FIFO模块原理与实现的文章就介绍到这儿,希望我们推荐的文章对编程师们有所帮助!