Communication method, communication system, sensor controller, and stylus

A communication method in a system including a first stylus that operates in a first mode in which bidirectional communication is performed or a second stylus that operates in a second mode in which bidirectional communication or unidirectional communication is performed, and a dual mode controller connected to a sensor that capacitively couples to the first stylus or the second stylus, wherein communication between the first stylus or the second stylus and the dual mode controller is performed by changing an electric field between the first stylus or the second stylus and the sensor, the communication method comprising:

• performing, by the dual mode controller, a dual mode discovery process in which a first discovery process and a second discovery process are alternately performed,
• the first discovery process including:
• transmitting, by the dual mode controller, a search signal for detecting the first stylus, performing processing to detect, by the dual mode controller, a response signal transmitted by the first stylus in response to the search signal, and extracting from the response signal, by the dual mode controller, function information that describes a function of the first stylus, and
• the second discovery process including:
• performing processing to detect a signal transmitted by the second stylus;
• determining, by the dual mode controller, that a mode of the dual mode controller is the first mode in response to detecting the response signal transmitted by the first stylus in response to the search signal;
• determining, by the dual mode controller, that the mode of the dual mode controller is the second mode in response to detecting the signal transmitted by the second stylus while the second discovery process is being performed;
• receiving, by the dual mode controller operating in the determined mode, a signal transmitted from one of the first stylus and the second stylus;
• and
• while the dual mode controller is operating in the second mode, supporting, by the dual mode controller, the function of the first stylus based on the function information and determining an operating mode of the dual mode controller based on the function information.