SPI模式下的PIC24F MSSP模块

大家好，我的SPI通讯有点问题。当我在示波器上检查我的信号时，我没有CS，但是我可以看到我的数据和时钟。我把我的代码放在下面来理解我的问题。谢谢你，安娜。



      以下为原文

    Hi everyone,
I have some trouble with my spi communication. When i check my signals on the oscilloscope, I don't have CS but i can see my data and clock.
I put my code below to understand my problem.
Thank you , Anaëlle

// FBS
#pragma config BWRP = OFF // Boot Segment Write Protect (Disabled)
#pragma config BSS = OFF // Boot segment Protect (No boot flash segment)

// FGS
#pragma config GWRP = OFF // General Segment Flash Write Protect (General segment may be written)
#pragma config GSS0 = OFF // General Segment Code Protect (No Protection)

// FOSCSEL
#pragma config FNOSC = FRCDIV // Oscillator Select (8MHz FRC with Postscaler (FRCDIV))
#pragma config SOSCSRC = ANA // SOSC Source Type (Analog Mode for use with crystal)
#pragma config LPRCSEL = HP // LPRC Power and Accuracy (High Power/High Accuracy)
#pragma config IESO = ON // Internal External Switch Over bit (Internal External Switchover mode enabled (Two-speed Start-up enabled))

// FOSC
#pragma config POSCMD = NONE // Primary Oscillator Mode (Primary oscillator disabled)
#pragma config OSCIOFNC = OFF // CLKO Pin I/O Function (CLKO output signal enabled)
#pragma config POSCFREQ = MS // Primary Oscillator Frequency Range (Primary Oscillator/External Clock frequency between 100kHz to 8MHz)
#pragma config SOSCSEL = SOSCHP // SOSC Power Selection Configuration bits (Secondary Oscillator configured for high-power operation)
#pragma config FCKSM = CSECMD // Clock Switching and Monitor Selection (Clock Switching Enabled; Fail-safe Clock Monitor Disabled)

// FWDT
#pragma config WDTPS = PS32768 // Watchdog Timer Postscale Select bits (1:32768)
#pragma config FWPSA = PR128 // WDT Prescaler bit (WDT prescaler ratio of 1:128)
#pragma config FWDTEN = OFF // Watchdog Timer Enable bits (WDT disabled in hardware; SWDTEN bit disabled)
#pragma config WINDIS = OFF // Windowed Watchdog Timer Disable bit (Standard WDT selected (windowed WDT disabled))

// FPOR
#pragma config BOREN = BOR3 // Brown-out Reset Enable bits (Enabled in hardware; SBOREN bit disabled)
#pragma config PWRTEN = ON // Power-up Timer Enable (PWRT enabled)
#pragma config I2C1SEL = PRI // Alternate I2C1 Pin Mapping bit (Default SCL1/SDA1 Pins for I2C1)
#pragma config BORV = V18 // Brown-out Reset Voltage bits (Brown-out Reset at 1.8V)
#pragma config MCLRE = ON // MCLR Pin Enable bit (RA5 input disabled; MCLR enabled)

// FICD
#pragma config ICS = PGx3 // ICD Pin Placement Select (EMUC/EMUD share PGC3/PGD3)

#include "p24F16KL402.h"

#define SPI_MASTER 0x30
#define SPI_ENABLE 0x40
int i=4;

void SPI1Init(){
    SSP1CON1 = SPI_MASTER; //Select Mode
    SSP1STAT = SPI_ENABLE; //Enable peripheral
}
int writeSPI1(unsigned char i) {
    SPI1BUF =i; //write to buffer for TX
    while (!SSP1STATbits.BF); //wait for transfer to complete
    return SPI1BUF; //read the received value
}

int main(void)
{
    SPI1Init();
    while(1)
    {
       writeSPI1(i);
    }
}