PIC18F46J50 I2C不能使用SSPxIF来检测字节传输完成

我写PIC18F46J50 I2C有困难。我希望有人能对这件事有所启发。2011 PIC18F46J50数据表通知我们，当使用PIC18F46J50作为主机通过I2C传输字节时，我们通过写入SSPXBUF开始每个字节传输。这设置缓冲满标志（BF）并开始移出字节。在移出第八位之后，清除缓冲器全标志（BF）。然后，发送额外的时钟以允许从属者相应地响应ACK或NACK。在第九时钟之后，SSPXIF位被设置，主时钟被挂起，直到下一个数据字节被加载到SSPXBUF中。我解释这意味着使用SPSSIF来确定字节已经被发送和ACK或NACK收到。在我的小例子中，我正在发送一个控制。（写入）字节，后面是一个地址字节，后面是一个SIR数据字节。在试图使事物工作时，我使用轮询方法，因此用WHELLY（）语句执行块，该语句等待FrsSPXIF在发送下一个字节之前被设置。然而，我的逻辑分析器显示只有第一个字节和第三个字节被传输。我已经确定第二个字节会丢失或被践踏，这是为什么？我们不能相信SPXIF与设备数据表相反吗？Windows 7（64位）MPLABX 4.01XC81.41感谢。这里是我的小例子。



      以下为原文

    I am having trouble writing PIC18F46J50 I2C. I hope someone can shed some light on the matter?

The 2011 PIC18F46J50 datasheet informs us that when using PIC18F46J50 as master to transmit a byte via I2C, we begin each byte transmission by writing to SSPxBUF. This sets the buffer full flag (BF) and begins shifting out the byte. After the eighth bit has been shifted out the buffer full flag (BF) is cleared. An extra clock is then transmitted to allow the slave to respond with ACK or NACK accordingly. After the ninth clock the SSPxIF bit is set and the master clock is suspended until the next data byte is loaded into SSPxBUF.

I interpret this to mean that use SSPxIF being set to determine that the byte has been transmitted and ACK or NACK received.

In my trivial example I am transmitting a control (write) byte, followed by a single address byte, followed by a sing data byte. In trying to get things working I am using a polling method and so block execution with a while() statement which waits for SSPxIF to be set before transmitting the next byte.

However, my logic analyser shows that only the first and third bytes are being transmitted. I have established that the second byte is getting lost or trampled.

Why is this? Can we not trust SSPxIF contrary to the device datasheet?

Windows 7 (64-bit)
MPLABX 4.01
XC8 1.41

Thanks.

Here is my trivial example.





/********************************************************************
* Project: TestI2C
* Module: main.c
* Created: 28Oct17
* Compiler: XC8 1.41
********************************************************************
* This USB device is powered by internal source - not USB bus.
*
*/



/** CONFIGURATION Bits **********************************************/
#pragma config WDTEN = OFF //WDT disabled (enabled by SWDTEN bit)
//#pragma config PLLDIV = 3 //Divide by 3 (12 MHz oscillator input)
#pragma config PLLDIV = 2 //JGB Divide by 2 (internal 8MHz input)
#pragma config STVREN = ON //stack overflow/underflow reset enabled
#pragma config XINST = OFF //Extended instruction set disabled
#pragma config CPUDIV = OSC1 //No CPU system clock divide
#pragma config CP0 = OFF //Program memory is not code-protected
//#pragma config OSC = HSPLL //HS oscillator, PLL enabled, HSPLL used by USB
#pragma config OSC = INTOSCPLL //JGB Internal OSC with PLL
#pragma config FCMEN = OFF //Fail-Safe Clock Monitor disabled
#pragma config IESO = OFF //Two-Speed Start-up disabled
#pragma config WDTPS = 32768 //1:32768
#pragma config DSWDTOSC = INTOSCREF //DSWDT uses INTOSC/INTRC as clock
#pragma config DSBOREN = OFF //Zero-Power BOR disabled in Deep Sleep
#pragma config DSWDTEN = OFF //Disabled
#pragma config DSWDTPS = 8192 //1:8,192 (8.5 seconds)
#pragma config IOL1WAY = OFF //IOLOCK bit can be set and cleared
#pragma config MSSP7B_EN = MSK7 //7 Bit address masking
#pragma config WPFP = PAGE_1 //Write Protect Program Flash Page 0
#pragma config WPEND = PAGE_0 //Start protection at page 0
#pragma config WPCFG = OFF //Write/Erase last page protect Disabled
#pragma config WPDIS = OFF //WPFP[5:0], WPEND, and WPCFG bits ignored
#pragma config T1DIG = ON //Sec Osc clock source may be selected
#pragma config LPT1OSC = OFF //high power Timer1 mode




#include



#define I2CDEV_RTCC_R 0xDF
#define I2CDEV_RTCC_W 0xDE

#define I2CDEV_SCL_TRIS TRISBbits.TRISB4
#define I2CDEV_SDA_TRIS TRISBbits.TRISB5

#define I2CDEV_SEND_ACK SSP1CON2bits.ACKDT=0, SSP1CON2bits.ACKEN=1;while(SSP1CON2bits.ACKEN)
#define I2CDEV_SEND_NACK SSP1CON2bits.ACKDT=1, SSP1CON2bits.ACKEN=1;while(SSP1CON2bits.ACKEN)
#define I2CDEV_SEND_RESTART SSP1CON2bits.RSEN=1;while(SSP1CON2bits.RSEN)
#define I2CDEV_SEND_START SSP1CON2bits.SEN=1;while(SSP1CON2bits.SEN)
#define I2CDEV_SEND_STOP SSP1CON2bits.PEN=1;while(SSP1CON2bits.PEN)



/********************************************************************
* MAIN
*******************************************************************/
int main(void) {

    TRISBbits.TRISB3 = 0; //Set output for SMD LED
    LATBbits.LATB3 = 0;

    //Enable the PLL and wait 2+ms until the PLL locks before enabling USB module
    {
     unsigned int pll_startup_counter = 600;
     OSCTUNEbits.PLLEN = 1;
     while(pll_startup_counter--);
    }

    //Setup I2C
    I2CDEV_SCL_TRIS = 1;
    I2CDEV_SDA_TRIS = 1;

    SSP1ADD = 0x77; //I2C = 100kHz @ 48MHz Fosc

    SSP1STAT = 0x00; //Power-on default
    SSP1STATbits.SMP = 0; //Slew = OFF for 100Hz

    SSP1CON1 = 0x00; //Power-on default
    SSP1CON1bits.SSPEN = 1; //Enable I2C and config pins

    SSP1CON1bits.SSPM3 = 1; //I2C Master mode, Clock = FOSC/(4 * (SSPxADD + 1))
    SSP1CON1bits.SSPM2 = 0;
    SSP1CON1bits.SSPM1 = 0;
    SSP1CON1bits.SSPM0 = 0;

    SSP1CON2 = 0x00; //Power-on default


    /****************************************************************
     * MAIN LOOP
     ***************************************************************/
    while(1) {

        //Create approx. 1 second delay
        for(unsigned int i = 0; i < 1024; i++) {
            for(unsigned int i = 0; i < 1024; i++);
        }

        //Flash confidence LED
        LATBbits.LATB3 = ~LATBbits.LATB3;


        //Send I2C write sequence
        I2CDEV_SEND_START;

        SSP1BUF = I2CDEV_RTCC_W;
        while(!PIR1bits.SSP1IF);
        PIR1bits.SSP1IF = 0;

        SSP1BUF = 0x00;
        while(!PIR1bits.SSP1IF);
        PIR1bits.SSP1IF = 0;

        SSP1BUF = 0x80;
        while(!PIR1bits.SSP1IF);
        PIR1bits.SSP1IF = 0;

        I2CDEV_SEND_STOP;

    }
}
/* end */

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