Digital to Analog converter by LPC1114 and MCP4922 (use Mbed complier)

                                                               Fig.2 MCP 4922 IC chip               

                                                                        Fig.3  Circuit
                             
 Code:
#include “mbed.h”

SPI spi(dp2, dp1, dp6); // mosi, miso, sclk
DigitalOut cs(dp14);
void sin_wave(float hz){
     int T_ =(int)((1.0/hz)*1000.0);
     for(int i=0;i<T_;i++){
           int k =4096/2+(int)(4096.0/2.0*sin((float)(i*4095.0/T_)/4095.0*2.0*3.1416));
           cs=0;
           spi.write((k>> 8)|0x30);
           spi.write(k&0xff);
           cs=1;
           wait_us(500);
        }
}
void saw_wave(float hz){
     int T_ =(int)((1.0/hz)*1000.0);
     for(int i=0;i<T_;i++){
           int k =(int)((float)i*4095.0/T_);
           cs=0;
           spi.write((k>> 8)|0x30);
           spi.write(k&0xff);
           cs=1;
           wait_us(500);
        }
}
int main() {
    int count_=0;
    spi.format(8,0);
    spi.frequency(10000000);
    while(1) {
        count_++;
        if(count_<=5){
            sin_wave(1.0);
        }
        else if(count_>5&&count_<=10){
            saw_wave(1.0);       
        }
        else if (count_>10){
            count_=0;
        }
    }
}