Physical computing, which builds interactive systems between the physical world and computers, has been widely used in a wide variety of domains and applications, e.g., the Internet of Things (IoT). Although physical computing has witnessed enormous realisations, testing these physical computing systems still face many challenges, such as potential circuit related bugs which are not part of the software problems, the timing issue which decreasing the testability, etc.; therefore, we proposed a mutation testing approach for physical computing systems to enable engineers to judge the quality of their tests in a more accurate way. The main focus is the communication between the software and peripherals. More particular, we first defined a set of mutation operators based on the common communication errors between the software and peripherals that could happen in the software. We conducted a preliminary experiment on nine physical computing projects based on the Raspberry Pi and Arduino platforms. The results show that our mutation testing method can assess the test suite quality effectively in terms of weakness and inadequacy.