STC的SPI输出的CLK的波形为什么是这样，为什么不是标准的方波

heat · 发表于 2014-8-1 21:55:07

[mw_shl_code=c,true]#include<reg52.h> //包含头文件，一般情况不需要改动，头文件包含特殊功能寄存器的定义 #include<intrins.h> #include<math.h> #include<stdio.h> #include<absacc.h> #include<ctype.h> #include<stdlib.h> #define MEAS 0x00 //测量模式 #define RWTR 0x08 //读写温度数据寄存器 #define STX 0x0E //x通道自检 #define STY 0x0F //Y通道自检 #define RDAX 0x10 //读Ｘ通道加速度值 #define RDAY 0x11 //读Ｙ通道加速度值 sbit SCK=P1^7; //定义端口 sbit MISO=P1^6; sbit MOSI=P1^5; sbit CSB=P1^4; unsigned int SPI_ReadBits(unsigned char n ); void SPI_WriteByte( unsigned char wdata ); void SPI_Start(void); void SPI_Stop(void); void SPI_Reset(void); void SPI_Delay(unsigned char); unsigned int SPI_GetX( void ); unsigned int SPI_GetY( void ); void SPI_Init( void ); sbit P0_0 = P0^0; sbit P0_1 = P0^1; sbit P0_2 = P0^2; sbit P0_3 = P0^3; sbit P0_4 = P0^4; sbit P0_5 = P0^5; sbit P0_6 = P0^6; sbit P0_7 = P0^7; sbit P1_0 = P1^0; sbit P1_1 = P1^1; sbit P1_2 = P1^2; sbit P1_3 = P1^3; sbit P1_4 = P1^4; sbit P1_5 = P1^5; sbit P1_6 = P1^6; sbit P1_7 = P1^7; sbit P2_0 = P2^0; sbit P2_1 = P2^1; sbit P2_2 = P2^2; sbit P2_3 = P2^3; sbit P2_4 = P2^4; sbit P2_5 = P2^5; sbit P2_6 = P2^6; sbit P2_7 = P2^7; sbit P3_0 = P3^0; sbit P3_1 = P3^1; sbit P3_2 = P3^2; sbit P3_3 = P3^3; sbit P3_4 = P3^4; sbit P3_5 = P3^5; sbit P3_6 = P3^6; sbit P3_7 = P3^7; void SPI_Stop( void ) { SCK = 0; CSB = 1; SPI_Delay(10); } void SPI_Reset(void) { SPI_Stop(); } void SPI_Delay(unsigned char n) { while(n--); } void SPI_Start(void) { SCK = 0; CSB = 0; SPI_Delay(10); } //主机写一个BYTE到器件 //最终状态:CLK　=　LOW void SPI_WriteByte( unsigned char wdata ) { unsigned char i; for( i = 0 ; i < 8 ; ++i ) { SCK = 0; SPI_Delay(10); MOSI = wdata & 0x80; wdata = wdata << 1; SPI_Delay(10); SCK = 1; SPI_Delay(10); } SCK = 0; } //主机读入N个比特 //n 限制为16及其以下 //结束状态　CLK　=　0 unsigned int SPI_ReadBits( unsigned char n ) { unsigned int rtemp,i; MISO = 1; for( i = 0 ; i < n ; ++i ) { rtemp <<= 1 ; SPI_Delay(10); if( MISO == 1 ){ rtemp |= 0x0001; }else{ rtemp &= 0xFFFE; } SCK = 1; SPI_Delay(10); SCK = 0; SPI_Delay(10); } return rtemp; } unsigned int SPI_GetX( void ) { unsigned int result; SPI_Start(); SPI_WriteByte( RDAX ); result = SPI_ReadBits(11); SPI_Stop(); return result; } unsigned int SPI_GetY( void ) { unsigned int result; SPI_Start(); SPI_WriteByte( RDAY ); result = SPI_ReadBits(11); SPI_Stop(); return result; } void SPI_Init( void ) { SPI_Start(); SPI_WriteByte( MEAS ); SPI_Stop(); } main() { unsigned int result; SPI_Reset(); SPI_Delay(1000); SPI_Init(); SPI_Delay(1000); while(1){ result = SPI_GetX(); } } [/mw_shl_code]