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楼主 |
发表于 2008-3-6 15:34:01
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马老师：您好！
感谢您的祝贺。我会按照老师的指点去做的。VB6.0的书已经到常州图书馆借了2本，准备学习了。
我在做一个RS485多机通讯的实验。主、从机的原理图都相同如下：
http://www.ouravr.com/bbs/bbs_upload19801/files_9/ourdev_221275.jpg
图中有一个元件RSM485CHT是周立功公司的,它有一个引脚“con”,当单片机发送的时候con要置0，当单片机接收的时候con要置1.下面这段程序是马老师书上的。//**********************是我添上去的语句。
硬件用rs232通讯，用“切换卡测试”程序测试是正常的。
硬件改用rs485通讯，用“切换卡测试”程序测试显示如图。PA7控制的led灯常亮。
1
下面是程序：请马老师看看我修改的错在哪里?
/*****************************************************
File name : demo_14_1.c
Chip type : ATmega16L
Program type : Application
Clock frequency : 11.059200 MHz
Memory model : Small
External SRAM size : 0
Data Stack size : 256
*****************************************************/
#include <mega16.h>
#define UART_BEGIN_STX 0xBB
#define UART_END_STX 0xEE
#define BAUD 9600 //波特率采用9600bps
#define CRYSTAL 11059200 //系统时钟11.0592MHz
//计算和定义波特率设置参数
#define BAUD_SETTING (unsigned int)((unsigned long)CRYSTAL/(16*(unsigned long)BAUD)-1)
#define BAUD_H (unsigned char)(BAUD_SETTING>>8)
#define BAUD_L (unsigned char)(BAUD_SETTING)
#define RXB8 1
#define TXB8 0
#define UPE 2
#define OVR 3
#define FE 4
#define UDRE 5
#define RXC 7
#define FRAMING_ERROR (1<<FE)
#define PARITY_ERROR (1<<UPE)
#define DATA_OVERRUN (1<<OVR)
#define DATA_REGISTER_EMPTY (1<<UDRE)
#define RX_COMPLETE (1<<RXC)
#define TX_BUFFER_SIZE 5
unsigned char tx_buffer[TX_BUFFER_SIZE]; // USART Transmitter buffer
unsigned char tx_wr_index,tx_rd_index,tx_counter;
// USART Transmitter interrupt service routine
interrupt [USART_TXC] void usart_tx_isr(void)
{
if (tx_counter)
{
--tx_counter;
PORTD.6=0; //***************
UDR=tx_buffer[tx_rd_index];
if (++tx_rd_index == TX_BUFFER_SIZE) tx_rd_index=0;
}
}
void putchar(unsigned char c)
{
while (tx_counter == TX_BUFFER_SIZE);
#asm("cli")
if (tx_counter || ((UCSRA & DATA_REGISTER_EMPTY)==0))
{
tx_buffer[tx_wr_index]=c;
if (++tx_wr_index == TX_BUFFER_SIZE) tx_wr_index=0;
++tx_counter;
}
else
PORTD.6=0; //***************
UDR=c;
#asm("sei")
}
#define RX_BUFFER_SIZE 5
unsigned char rx_buffer[RX_BUFFER_SIZE]; // USART Receiver buffer
unsigned char rx_counter;
bit Uart_RecvFlag;
// USART Receiver interrupt service routine
interrupt [USART_RXC] void usart_rx_isr(void)
{
unsigned char status,data;
status = UCSRA;
PORTD.6=1; //***********************
data = UDR;
if (!Uart_RecvFlag) // 判断是否允许接收一个新的数据包
{
if ((status & (FRAMING_ERROR | PARITY_ERROR | DATA_OVERRUN))==0)
{
rx_buffer[rx_counter] = data;
rx_counter++;
switch (rx_counter)
{
case 1: // 检验起始字符
if (data != UART_BEGIN_STX) rx_counter = 0;
break;
case 4: // 检验校验字
if (data != (rx_buffer[1]^rx_buffer[2])) rx_counter = 0;
break;
case 5: // 检验结束字符
rx_counter = 0;
if (data == UART_END_STX) Uart_RecvFlag = 1;
break; // Uart_RecvFlag=1，表示正确接收到一个数据包
}
}
}
}
void main(void)
{
unsigned char channel = 0x07;
unsigned char tx_1,tx_3;
PORTD=0xff; //***************
DDRD=0xFF; //***************
PORTA = ~(0x01<<channel);
DDRA=0xFF;
// USART initialization
UCSRA=0x00; // Communication Parameters: 8 Data, 1 Stop, No Parity
UCSRB=0xD8; // USART Receiver: On, USART Transmitter: On
UCSRC=0x86; // USART Mode: Asynchronous, USART Baud Rate: 9600
UBRRH = BAUD_H; // 设置波特率
UBRRL = BAUD_L;
#asm("sei") // Global enable interrupts
while (1)
{
if (Uart_RecvFlag)
{ // 有刚接收到数据包需要处理
tx_1 = 0x00;
switch (rx_buffer[1]) // 数据包处理过程
{
case 0xA0:
break;
case 0xA1:
if (rx_buffer[2]>=0x00 && rx_buffer[2]<=0x07)
{
channel = rx_buffer[2];
PORTA = ~(0x01<<channel);
}
else
tx_1 = 0x02;
break;
default:
tx_1 = 0x01;
break;
}
tx_3 = tx_1^channel;
putchar(UART_BEGIN_STX); // 发送回送数据包
putchar(tx_1);
putchar(channel);
putchar(tx_3);
putchar(UART_END_STX);
Uart_RecvFlag = 0; // 允许接收下一个数据包
}
}
} |
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发表于 2008-3-4 15:40:19
