use MCP4922 with pic18f4553

main.c

/*
 * File:   main.c
 * Author: thotgamma
 *
 * Created on August 4, 2018, 4:31 AM
 */

#pragma config FOSC  = HS       // 20MHz Xtal(分周なし)
#pragma config MCLRE = ON       // リセットピンを利用する
#pragma config LVP   = OFF      // 低電圧プログラミング機能使用しない(OFF)
#pragma config WDT   = OFF      // ウォッチドッグタイマーを利用しない

#define _XTAL_FREQ 20000000


#include <xc.h>
#include <stdint.h>
#include <stdbool.h>



void SPIWrite(uint16_t data) {
    
    uint8_t dummy;
    
    LATBbits.LATB3 = 0;
    
    SSPBUF = (uint8_t)((data & 0xFF00) >> 8);
    while(!SSPSTATbits.BF);
    dummy = SSPBUF;
    
    SSPBUF = (uint8_t)(data & 0x00FF);
    while(!SSPSTATbits.BF);
    dummy = SSPBUF;
    
    LATBbits.LATB3 = 1;
    
    LATBbits.LATB2 = 0;
    __delay_us(1);
    LATBbits.LATB2 = 1;
    
    
}

void main(void) {
    
    ADCON1  =	0b00001111;
    TRISA   =	0b00000000;
    TRISB   =	0b00000000;
    TRISC   =	0b00110000;         //D-,D+
    TRISD   =	0b00000000;
    TRISE   =   0b00000011;         //SW1,2=INPUT LED=OUTPUT
    LATA    =	0b00000000;
    LATB    =	0b00001100;
    LATC    =	0b00000000;
    LATD    =	0b00000000;
    LATE    =	0b00000000;

    SSPSTAT = 0b01000000;
    SSPCON1 = 0b00100000;
    
    uint16_t value = 0;
    bool mode = false;
    while (true) {
        /*
        if (mode) {
            SPIWrite(0x7FFF);
        } else {
            SPIWrite(0x7000);
        }
        mode = ~mode;
        */
//        /*
        SPIWrite(0x7000 | value);
        value += 0xFF;
        if (value >= 0x1000) value = 0;
//        */
    }
    
    return;
}