File content as of revision 0:f2657b94ea70:

#include "mbed.h"
 
Serial uart(USBTX, USBRX); 
//Serial uart(D10,D2);            // TX : D10     RX : D2           // blueteeth
DigitalOut LED(A4);            // check if the code is running

// timer
Ticker timer1;
float ITR_time1 = 10000.0;  // unit：ms


// encoder
DigitalOut encoder_cs(D9);
SPI spi_encoder(D11, D12, D13); // mosi, miso, sclk
unsigned short encoder_value = 0;
unsigned short angle = 0;
unsigned short angle_old;
unsigned short angle_init;
int angle_dif;
int a_dif;
int Angle;
unsigned short k = 0;

// uart_tx
union splitter {
    short j;
    char C[2];
    // C[0] is lowbyte of j, C[1] is highbyte of j
};
char T[16] = {255,255,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
int i = 0;

// function
void init_encoder();
void init_SPI();
void init_UART();
void init_TIMER();
void timer1_ITR();
void angle_measure();
int angle_count(unsigned short,unsigned short);
void uart_tx();


int main()
{
    LED = 1;
    wait_ms(500);
    // initial sensor
    init_encoder();
    init_SPI();
    // initial uart
    init_UART();
    
    wait_ms(500);
    LED = 0;
    
    init_TIMER();
    
    while(1) {
    }
    
}

void init_encoder()
{
//    encoder_cs = 1;  // disable encoder
    
    encoder_cs = 0; // Select the device by seting chip select low
    encoder_value = spi_encoder.write(0x00);
    angle_init = encoder_value >> 3;
    encoder_cs = 1; // Deselect the device
    
}

void init_SPI()
{
    spi_encoder.format(16,3);
    spi_encoder.frequency(1000000); // 1MHz clock rate
}

void init_UART()
{
    uart.baud(115200);
}

void init_TIMER()
{
    timer1.attach_us(&timer1_ITR, ITR_time1);
}

void timer1_ITR()
{
    angle_measure();
//    angle_count();
    uart_tx();
}

void angle_measure()
{    
    encoder_cs = 0; // Select the device by seting chip select low
    encoder_value = spi_encoder.write(0x00);
    angle = encoder_value >> 3;
    encoder_cs = 1; // Deselect the device
    
    if (k == 0)
    {
        angle_dif = angle_count(angle, angle_init);
        Angle = angle_init + angle_dif;
        angle_old = angle;
        k++;
//        angle_dif = angle_count();
//        Angle = angle_init + angle_dif;
//        angle_old = angle;
//        k++;
    }
    else
    {
        angle_dif = angle_count(angle, angle_old);
        Angle = Angle + angle_dif;
        angle_old = angle;
    }
}    

int angle_count(unsigned short now,unsigned short old)
{
    a_dif = now - old;
    if (a_dif > 4096/2)
        a_dif = -(4096 - a_dif);
    else if (a_dif < -4096/2)
        a_dif = 4096 + a_dif;
    else
        a_dif = a_dif;
    
    return a_dif;
}

void uart_tx()
{
    splitter s1;
    splitter s2;
    splitter s3;
    splitter s4;
    splitter s5;
    splitter s6;
    splitter s7;
    
    s1.j = angle;
    s2.j = Angle;
    s3.j = 2;
    s4.j = 3;
    s5.j = 1;
    s6.j = 2;
    s7.j = 3;
    
    T[2] = s1.C[0];
    T[3] = s1.C[1];
    T[4] = s2.C[0];
    T[5] = s2.C[1];
    T[6] = s3.C[0];
    T[7] = s3.C[1];
    T[8] = s4.C[0];
    T[9] = s4.C[1];
    T[10] = s5.C[0];
    T[11] = s5.C[1];
    T[12] = s6.C[0];
    T[13] = s6.C[1];
    T[14] = s7.C[0];
    T[15] = s7.C[1];
    
    while(1) {
        if (uart.writable() == 1) {
            uart.putc(T[i]);
            i++;
        }
        if (i >= (sizeof(T)-1)) {
            i = 0;
            break;
        }
    }
}