A control method for a first communication device , wherein the first communication device and a second communication device are connected through a communication bus, and the control method comprises the steps of periodically outputting a first level signal and a second level signal to the communication bus, wherein the second communication device establishes a data connection with the first communication device based on when a level signal on the communication bus is the first level signal, and the second communication device establishes a power supply connection with the first communication device based on when the level signal on the communication bus is the second level signal, wherein the step of periodically outputting the first level signal and the second level signal to the communication bus comprises the steps of : outputting the first level signal to the communication bus at each cycle; and determining whether a duration of the communication bus outputting the first level signal is greater than or equal to a first duration, and outputting the second level signal to the communication bus, wherein duration of the first communication device outputting the second level signal to the communication bus is greater than or equal to a second duration; sending data to the second communication device based on when a level signal on the communication bus is switched from the second level signal to the first level signal; and sending data to the second communication device in a form of the first signal and/or the second signal, wherein the first signal comprises the second level signal and a third level signal and the sum of duration of the second level signal and duration of the third level signal is target duration, the second signal comprises the second level signal, and duration of the second level signal is target duration. periodically outputting a first level signal and a second level signal to the communication bus, wherein the second communication device establishes a data connection with the first communication device based on when a level signal on the communication bus is the first level signal, and the second communication device establishes a power supply connection with the first communication device based on when the level signal on the communication bus is the second level signal, wherein the step of periodically outputting the first level signal and the second level signal to the communication bus comprises the steps of : outputting the first level signal to the communication bus at each cycle; and determining whether a duration of the communication bus outputting the first level signal is greater than or equal to a first duration, and outputting the second level signal to the communication bus, wherein duration of the first communication device outputting the second level signal to the communication bus is greater than or equal to a second duration; sending data to the second communication device based on when a level signal on the communication bus is switched from the second level signal to the first level signal; and sending data to the second communication device in a form of the first signal and/or the second signal, wherein the first signal comprises the second level signal and a third level signal and the sum of duration of the second level signal and duration of the third level signal is target duration, the second signal comprises the second level signal, and duration of the second level signal is target duration. <EOS>