Fixed services for parameter adjusting not working

mg_control/src/mg_control.cpp

@@ -66,14 +66,18 @@ hardware_interface::return_type mg::MgStepperInterface::read(const rclcpp::Time&
 }
 
 hardware_interface::return_type mg::MgStepperInterface::write(const rclcpp::Time&, const rclcpp::Duration&) {
-    std::string cmd_left;
-    std::string cmd_right;
-
-    cmd_left  = std::to_string(left_wheel_vel_cmd / (2 * M_PI)) + " ";
-    cmd_right = std::to_string(-right_wheel_vel_cmd / (2 * M_PI));
+    union {
+        std::array<u_char, sizeof(double)> bytes;
+        double                             data;
+    } value{};
 
     try {
-        odrive_serial_interface.Write(cmd_left + cmd_right);
+        odrive_serial_interface.Write("s;");
+        value.data = left_wheel_vel_cmd / (2 * M_PI);
+        for (const auto& bt : value.bytes) { odrive_serial_interface.WriteByte(bt); }
+        value.data = -right_wheel_vel_cmd / (2 * M_PI);
+        for (const auto& bt : value.bytes) { odrive_serial_interface.WriteByte(bt); }
+
     } catch (const std::runtime_error& e) { return hardware_interface::return_type::ERROR; }
     return hardware_interface::return_type::OK;
 }