Method for reducing influence of noise on signal line, decoding circuit and power providing/receiving device using the same
A method for reducing influence of noise on a signal line, a decoding circuit and a power provider are disclosed. The method includes steps of: dividing an analog signal to be decoded into levels; determining the level of the analog signal and acquiring the current level of the analog signal to be decoded to obtain a current level number; updating a highest level variable when the current level number is greater than the highest level variable; updating a lowest level variable when the current level number is smaller than the lowest level variable; and outputting an edge detection pulse and setting the highest level variable and the lowest level variable equal to the current level number when the difference between the highest level variable and the lowest level variable is greater than a noise tolerance value.
1 . A decoding circuit, comprising:
a plurality of comparators, wherein each of the plurality of comparators comprises a first terminal, a second terminal and an output terminal, the first terminal of each of the plurality of comparators receives an analog signal to be decoded, and the second terminal of each of the plurality of comparators is coupled to a corresponding reference voltage level, wherein each of the plurality of reference voltage levels is distinct;
a noise filtering and signal edge detection circuit, coupled to the output terminals of the plurality of comparators;
wherein the noise filtering and signal edge detection circuit determines a current level of the analog signal to be decoded based on signals output from the output terminals of the comparators to obtain a current level number;
wherein the noise filtering and signal edge detection circuit has a highest level variable and a lowest level variable therein;
wherein when the current level number is greater than the highest level variable, the highest level variable is updated to the current level number;
wherein when the current level number is smaller than the lowest level variable the lowest level variable is updated to the current level number;
wherein, when a difference between the lowest level variable and the highest level variable is greater than a noise tolerance value, the noise filtering and signal edge detection circuit outputs an edge detection pulse, sets the highest level variable and the lowest level variable as the current level number, and continuously determines the voltage level of the analog signal to be decoded to obtain the current level number;
wherein the decoding circuit further comprises:
a digital signal data processing circuit, coupled to an output terminal of the noise filtering and signal edge detection circuit, and generating a decoded signal based on the edge detection pulse.
2 . The decoding circuit of claim 1 , wherein the analog signal to be decoded is obtained from a channel configuration pin (CC pin) of a Universal Serial Bus (USB) connection port.
3 . The decoding circuit of claim 1 , wherein the analog signal to be decoded is modulated based on a bi-phase mark code (BMC), and the digital signal data processing circuit is a BMC decoding circuit.
4 . A power providing/receiving device, comprising:
a Universal Serial Bus (USB), comprising a channel configuration pin (CC pin), the power providing/receiving device being coupled to an exterior device through the USB;
a decoding circuit, comprising:
a plurality of comparators, wherein each of the plurality of comparators comprises a first terminal, a second terminal and an output terminal, the first terminal of each of the plurality of comparators is coupled to the CC pin and receives an analog signal to be decoded through the CC pin, and the second terminal of each of the plurality of comparators is coupled to a corresponding reference voltage level, wherein the plurality of reference voltage levels are distinct;
a noise filtering and signal edge detection circuit, coupled to the output terminals of the plurality of comparators;
wherein the noise filtering and signal edge detection circuit determines a current level of the analog signal to be decoded based on signals output from the output terminals of the comparators to obtain a current level number;
wherein the noise filtering and signal edge detection circuit has a highest level variable and a lowest level variable therein;
wherein when the current level number is greater than the highest level variable the highest level variable is updated to the current level number;
wherein when the current level number is smaller than the lowest level variable the lowest level variable is updated to the current level number;
wherein, when a difference between the lowest level variable and the highest level variable is greater than a noise tolerance value, the noise filtering and signal edge detection circuit outputs an edge detection pulse, sets the highest level variable and the lowest level variable as the current level number, and continuously determines the voltage level of the analog signal to be decoded to obtain the current level number;
wherein the decoding circuit further comprises:
a digital signal data processing circuit, coupled to an output terminal of the noise filtering and signal edge detection circuit, and generating a decoded signal based on a time period of the edge detection pulse;
wherein the power providing/receiving device further comprises:
a power providing/receiving circuit, coupled to a connection port of the USB, and receiving the decoded signal;
wherein the power providing/receiving circuit communicates with the coupled exterior device based on the decoded signal.
5 . The power providing/receiving device of claim 4 , wherein the analog signal to be decoded is modulated based on a bi-phase mark code (BMC), and the digital signal data processing circuit is a BMC decoding circuit.