File content as of revision 0:7e56d5ba2990:

#include "mbed.h"

Serial pc(USBTX, USBRX); // tx, rx


SPI spi(p5, p6, p7); // mosi, miso, sclk
DigitalOut rst_n(p8); // 
DigitalOut cs_n(p9);

// p5 : pin19 MOSI
// p6 : pin20 MISO
// p7 : pin01 SCLK
// p8 : pin04 RESET_N





int read_reg(int addr);
void write_reg(int addr,int data);

int read_reg(int addr) {
        int retval;
        cs_n=0;
        wait_us(4000);
        spi.write(0x21);
        wait_us(1000);
        spi.write(addr & 0xFF);
        wait_us(1000);
        retval = spi.write(0);
        wait_us(1000);        
        retval = spi.write(0);
        wait_us(4000);
        cs_n=1;
        return retval;    
}
    
void write_reg(int addr,int data){
        cs_n=0;
        wait_us(4000);
        spi.write(0x20);
        wait_us(1000);
        spi.write(addr & 0xFF);
        wait_us(1000);
        spi.write(data);
        wait_us(4000);
        cs_n=1;
}

int main() {
    int rw,addr,data;
    // 8-bit, SPI mode 2
    spi.format(8,2);
    // 10kHz
    spi.frequency(10000);

    pc.printf("Init device\r\n");

    cs_n  = 1;
    rst_n = 0;    
    wait_ms(10); 
    rst_n = 1;    

    while(1) {
        rw = -1;
        addr = 0;
        data = 0;
        pc.printf("Write and Read Address Data? rw(write=0,read=1) addr(hex) data(hex): \r\n");    
        pc.scanf("%d %x %x",&rw,&addr,&data);
        // Write
        cs_n=0;
        if ( rw == 0 ) {
            write_reg(addr,data);
            pc.printf("Wrote %02x @ %02x\r\n",data,addr);
            pc.printf("Read  %02x @ %02x\r\n",read_reg(addr),addr);
        }
        else if (rw == 1 ) {
            pc.printf("Read  %02x @ %02x\r\n",read_reg(addr),addr);
        }
        else if (rw == 2) {
            for (int i=0; i<10;i++){
                pc.printf("Read data %02x @ %02x\r\n",read_reg(i),i);
            }
        }
        else {
            pc.printf("Unknown command\r\n");
        }
    }
}