private void btnCloseIMU_Click(object sender, EventArgs e)
 {
     mf.CloseIMUPort();
     if (mf.spIMU.IsOpen)
     {
         cboxIMU.Enabled     = false;
         btnCloseIMU.Enabled = true;
         btnOpenIMU.Enabled  = false;
     }
     else
     {
         cboxIMU.Enabled     = true;
         btnCloseIMU.Enabled = false;
         btnOpenIMU.Enabled  = true;
     }
 }