micro:bit / I2C バス / オンボード加速度計 / I2C バスから 3 軸の 10 ビットデータを読み取る / mbed

#include "MicroBit.h"
MicroBit uBit;

float raw2g(int raw){
    if(0x200 == (0x200 & raw)){     // 0x200 = 0b 10 0000 0000
        raw -= 1024;                // 1024 = 2^10
    }
    return 0.00390625 * (float)raw; // 0.00390625 = 4/(2^10)
}

int main(void){
    uBit.init();
 
    char buf[] = {0x01};
    char buf2[6];
       
    while(1){
        uBit.i2c.write(0x1d<<1, buf, 1, true);        
        uBit.i2c.read(0x1d<<1, buf2, 6);
        
        int raw_x = (buf2[0]<<2) | (buf2[1]>>6);
        int raw_y = (buf2[2]<<2) | (buf2[3]>>6);
        int raw_z = (buf2[4]<<2) | (buf2[5]>>6);

        float x = raw2g(raw_x);
        float y = raw2g(raw_y);
        float z = raw2g(raw_z);

        printf("x: %.8f , y: %.8f , z: %.8f\n", x, y, z);
        wait_ms(1000);
    }
    
    release_fiber();
    return 0;
}

実行結果: