应用场景：

  主频不高非操作系统的单片机，需要在while循环中发送 数据到上位机，当数据较长时，会让发送的过程会让其他操作有卡顿感。为了解决这个问题，需采用一种方法：在每次大循环中只发一个字节数据，直到发送完毕。

#include <stdio.h>
#include <unistd.h>
void msleep(int ms)
{
	usleep(1000*ms);
}


//=============================================
#define MAX_SEND_LEN 10

u8 g_sendBuffer1[MAX_SEND_LEN]={ 0xa1,0xa2,0xa3,0xa4,0xa5,0xa6,0xa7,0xa8,0xa9,0xaa };
u8 g_sendBuffer2[MAX_SEND_LEN]={ 0xb1,0xb2,0xb3,0xb4,0xb5,0xb6,0xb7,0xb8,0xb9,0xba };


//用printf打印输出,模拟单片机发送单字符
void UART_Send_Byte(u8 ch)
{
	printf("%02X ",ch);
}

int loop_send_uart(u8 *data,int delaycnt )
{
	static int send_index = -1;
	static int send_delayCnt =0;

	send_index++;
	
	if( send_index == 0 )
	{
		send_delayCnt = delaycnt;
	}	
    else if( send_index >= MAX_SEND_LEN)
	{
		if(--send_delayCnt<=0)
		{
			send_index = -1;
			send_delayCnt = delaycnt;
			return 0xFF;//finish signal
		}	
		else
			return send_index;
	}	
	UART_Send_Byte( data[send_index] );
	return send_index;
}
 
int main(int argc, char **argv)
{
    printf("=======C_BuildTime=[%s]==============\r\n\r\n",__TIME__ );
	
	int cnt = 0;
	int ret_index = 0;
	while(1)
	{
		printf("A_count = %d ::", cnt++ );
		printf("send_DATA=[");
		ret_index = loop_send_uart(g_sendBuffer1,3);
		printf("],ret_index=%02x.\n",ret_index );
		msleep(500);
		if(ret_index==0xFF) //发送完第1组数据
			break;
	}
	
	while(1)
	{
		printf("B_count = %d ::", cnt++ );
		printf("send_DATA=[");
		ret_index = loop_send_uart(g_sendBuffer2,3);
		printf("],ret_index=%02x.\n",ret_index );
		msleep(500);
		if(ret_index==0xFF) //发送完第2组数据
			break;
	}	
    return 0;
}

运行结果如下：