关于SPI双机互为主从的通信
SPI单主单从试了很多次，数据总是乱飞，现在决定用互为主从通信，依然碰到错误，错误如下。每次开机后，主机发送数据给从机，从机返回这个数据到主机，但是主机收到的数据是0x00，开机后第一次通信总是这样，之后就正常了，第二次给从机发送数据就能返回正常的数据了。根据测试，从机收到的数据是正常的，但是将数据返回给主机，数据就不正常了，程序如下：#include "reg51.h"
#define FOSC 22118400L
#define BAUD (256 - FOSC / 32 / 115200)
typedef unsigned char BYTE;
typedef unsigned int WORD;
typedef unsigned long DWORD;
sfr AUXR = 0x8e; //Auxiliary register
sfr SPSTAT = 0xcd; //SPI status register
#define SPIF 0x80 //SPSTAT.7
#define WCOL 0x40 //SPSTAT.6
sfr SPCTL = 0xce; //SPI control register
#define SSIG 0x80 //SPCTL.7
#define SPEN 0x40 //SPCTL.6
#define DORD 0x20 //SPCTL.5
#define MSTR 0x10 //SPCTL.4
#define CPOL 0x08 //SPCTL.3
#define CPHA 0x04 //SPCTL.2
#define SPDHH 0x00 //CPU_CLK/4
#define SPDH 0x01 //CPU_CLK/16
#define SPDL 0x02 //CPU_CLK/64
#define SPDLL 0x03 //CPU_CLK/128
sfr SPDAT = 0xcf; //SPI data register
sbit SPISS = P1^3; //SPI slave select, connect to other MCU's SS(P1.4) pin
sfr IE2 = 0xAF; //interrupt enable rgister 2
#define ESPI 0x02 //IE2.1
void InitUart();
void InitSPI();
void SendUart(BYTE dat); //send data to PC
BYTE RecvUart(); //receive data from PC
bit MSSEL; //1: master 0:slave
///////////////////////////////////////////////////////////
void main()
{
InitUart(); //initial UART
InitSPI(); //initial SPI
IE2 |= ESPI;
EA = 1;
while (1)
{
if (RI)
{
SPCTL = SPEN | MSTR; //set as master
MSSEL = 1;
ACC = RecvUart();
SPISS = 0; //pull low slave SS
SPDAT = ACC; //trigger SPI send
}
}
}
///////////////////////////////////////////////////////////
void spi_isr() interrupt 9 using 1 //SPI interrupt routine 9 (004BH)
{
SPSTAT = SPIF | WCOL; //clear SPI status
if (MSSEL)
{
SPCTL = SPEN; //reset as slave
MSSEL = 0;
SPISS = 1; //push high slave SS
SendUart(SPDAT); //return received SPI data
}
else
{ //for salve (receive SPI data from master and
SPDAT = SPDAT; // send previous SPI data to master)
}
}
///////////////////////////////////////////////////////////
void InitUart()
{
SCON = 0x5a; //set UART mode as 8-bit variable baudrate
TMOD = 0x20; //timer1 as 8-bit auto reload mode
AUXR = 0x40; //timer1 work at 1T mode
TH1 = TL1 = BAUD; //11 5200 bps
TR1 = 1;
}
///////////////////////////////////////////////////////////
void InitSPI()
{
SPDAT = 0; //initial SPI data
SPSTAT = SPIF | WCOL; //clear SPI status
SPCTL = SPEN; //slave mode
}
///////////////////////////////////////////////////////////
void SendUart(BYTE dat)
{
while (!TI); //wait pre-data sent
TI = 0; //clear TI flag
SBUF = dat; //send current data
}
///////////////////////////////////////////////////////////
BYTE RecvUart()
{
while (!RI); //wait receive complete
RI = 0; //clear RI flag
return SBUF; //return receive data
} 求助！！！
页:
[1]