/*------------------------------------------------------------------*/
/* --- STC MCU International Limited -------------------------------*/
/* --- STC 1T Series MCU SPI Demo(Each other as the master-slave) --*/
/* --- Mobile: (86)13922805190 -------------------------------------*/
/* --- Fax: 86-755-82944243 ----------------------------------------*/
/* --- Tel: 86-755-82948412 ----------------------------------------*/
/* --- Web: www.STCMCU.com -----------------------------------------*/
/* If you want to use the program or the program referenced in the  */
/* article, please specify in which data and procedures from STC    */
/*------------------------------------------------------------------*/

#include "reg51.h"

#define FOSC        18432000L
#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

void InitUart();
void InitSPI();
void SendUart(BYTE dat);        //send data to PC
BYTE RecvUart();                //receive data from PC
BYTE SPISwap(BYTE dat);         //swap SPI data between master and slave

///////////////////////////////////////////////////////////

void main()
{
    InitUart();                 //initial UART
    InitSPI();                  //initial SPI

    while (1)
    {
        if (RI)
        {
            SPCTL = SPEN | MSTR; //set as master
            SendUart(SPISwap(RecvUart()));
            SPCTL = SPEN;		//reset as slave
        }
        if (SPSTAT & SPIF)
        {
            SPSTAT = SPIF | WCOL; //clear SPI status
            SPDAT = SPDAT;		//mov data from receive buffer to send buffer
        }
    }
}

///////////////////////////////////////////////////////////

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;           //115200 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
}

///////////////////////////////////////////////////////////

BYTE SPISwap(BYTE dat)
{
    SPISS = 0;                  //pull low slave SS
    SPDAT = dat;                //trigger SPI send
    while (!(SPSTAT & SPIF));   //wait send complete
    SPSTAT = SPIF | WCOL;       //clear SPI status
    SPISS = 1;                  //push high slave SS
    return SPDAT;               //return received SPI data
}