File content as of revision 0:1f873630ed4f:

#include "mbed.h"

Serial pc(SERIAL_TX, SERIAL_RX);


/* This example uses pins A0, A1 and A2 as SSC interface pins */
DigitalOut SCK( A0 );
DigitalInOut DATA( A2 );
DigitalOut CSQ( A1 );



/*Functions for bit level access to SSC bus */

inline void ssc_write_bit( int value ){
    SCK = 0;
    wait_us(1);
    SCK = 1;
    wait_us(1);
    if( value != 0 ){ DATA = 1; } else { DATA = 0; }
    wait_us(1);
    SCK = 0;
    }

inline int ssc_read_bit(){
    int out = 0;
    SCK = 0;
    wait_us(1);
    SCK = 1;
    
    wait_us(1);
    SCK = 0;
    if( DATA.read() != 0 ){ out = 1; }
    
    
    return out;
    }

/* Functions to read & write 16bit words via SSC */

void ssc_write_word( uint16_t word ){
    DATA.output();
    wait_us(1);
    for( int i = 0; i < 16 ; ++i ){
        ssc_write_bit( word & 0x8000 );
        word <<= 1;
        }
    }

uint16_t ssc_read_word(){
    uint16_t word = 0;
    DATA.input();
    wait_us(1);
    for( int i = 0; i < 16; ++i ){
        word <<= 1;
        word |= ssc_read_bit();
        }
   
    return word; 
    }

/* And function to read angle from GMR sensor  */
float encoder_read_angle(){
    uint16_t data[2] = {10,10};
    uint16_t cmd = 0x8000 | (2<<4) | 1;
    float angle;
    
    /* Request new measurement */    
    SCK = 0;
    CSQ = 0;
    wait_us(2);
    CSQ = 1;
    wait_us(2);
    
    /* Read angle register */
    SCK = 0;
    CSQ = 0;
    ssc_write_word( cmd );
    wait_us(2);
    data[0] = ssc_read_word(); /* angle */
    data[1] = ssc_read_word(); /* checksum */
    CSQ = 1;
    
    /* compute angle from measurement */
    angle = (0x7fff & data[0]) * 360.0f/(32768.0f);    
    
    return angle;
    }

int main() {
    pc.baud( 115200 );
    
    while(1) {
        float angle = encoder_read_angle();
        pc.printf( "Angle: %.2f deg\r\n", angle );
        wait( 0.25 );
        }
    }