(iOS)Accelerometer Graph(将g-force转换为/ -128)粒度

下图显示标签中的x,y,z值与图表上的输出不匹配:(请注意,addX：y：z值是图表上方标签中显示的值)

视图控制器

从蓝牙外设接收x,z值,然后使用以下转换：

// updates LABELS
- (void)didReceiveRawAcceleromaterDataWithX:(NSInteger)x Y:(NSInteger)y Z:(NSInteger)z
{
    dispatch_async(dispatch_get_main_queue(),^{
        _labelAccel.text = [NSString StringWithFormat:@"x:%li  y:%li  z:%li",(long)x,(long)y,(long)z];
    });
}

// updates GRAPHS
- (void)didReceiveAcceleromaterDataWithX:(NSInteger)x Y:(NSInteger)y Z:(NSInteger)z
{
    dispatch_async(dispatch_get_main_queue(),^{

        float xx = ((float)X) / 8192;
        float yy = ((float)y) / 8192;
        float zz = ((float)z) / 8192;

        [_xGraph addX:xx y:0 z:0];
        [_yGraph addX:0 y:yy z:0];
        [_zGraph addX:0 y:0 z:zz];

    });
}

GraphView

- (BOOL)addX:(UIAccelerationvalue)x y:(UIAccelerationvalue)y z:(UIAccelerationvalue)z
{
    // If this segment is not full,then we add a new acceleration value to the history.
    if (index > 0)
    {
        // First decrement,both to get to a zero-based index and to flag one fewer position left
        --index;
        xhistorY[index] = x;
        yhistorY[index] = y;
        zhistorY[index] = z;
        // And inform Core Animation to redraw the layer.
        [layer setNeedsDisplay];
    }
    // And return if we are Now full or not (really just avoids needing to call isFull after adding a value).
    return index == 0;
}

- (void)drawLayer:(CALayer*)l inContext:(CGContextRef)context
{
    // Fill in the BACkground
    CGContextSetFillColorWithColor(context,kUIColorLightGray(1.f).CGColor);
    CGContextFillRect(context,layer.bounds);

    // Draw the grid lines
    DrawGridlines(context,0.0,32.0);

    // Draw the graph
    CGPoint lines[64];
    int i;

    float _granularity = 16.f; // 16
    NSInteger _granualCount = 32; // 32

    // X
    for (i = 0; i < _granualCount; ++i)
    {
        lines[i*2].x = i;
        lines[i*2+1].x = i + 1;

        lines[i*2].y = xhistorY[i] * _granularity;
        lines[i*2+1].y = xhistorY[i+1] * _granularity;
    }
    CGContextSetstrokeColorWithColor(context,_xColor.CGColor);
    CGContextstrokeLinesegments(context,lines,64);

    // Y
    for (i = 0; i < _granualCount; ++i)
    {
        lines[i*2].y = yhistorY[i] * _granularity;
        lines[i*2+1].y = yhistorY[i+1] * _granularity;
    }
    CGContextSetstrokeColorWithColor(context,_yColor.CGColor);
    CGContextstrokeLinesegments(context,64);

    // Z
    for (i = 0; i < _granualCount; ++i)
    {
        lines[i*2].y = zhistorY[i] * _granularity;
        lines[i*2+1].y = zhistorY[i+1] * _granularity;
    }
    CGContextSetstrokeColorWithColor(context,_zColor.CGColor);
    CGContextstrokeLinesegments(context,64);
}

如何计算上述代码以精确显示图表上的正确加速度计值？