According to one embodiment, a communication system includes a controller and a plurality of devices serially connected to the controller by a communication path. Each device has a different identifying address from each other device. The communication path connects the controller to the plurality of devices in a loop. The communication path is configured to transmit a communication frame as a differential serial signal. The communication frame includes a plurality of packets. Each packet in the plurality of packets has a fixed data length. Each device is configured to insert data into, and extract data from, a packet in the communication frame.