Four-channel touch chip verification board

The function has not been verified by me, it is for reference only.

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* This project is used to verify the solution verification board design of the [Lichuang Mall](https://www.szlcsc.com/) four-channel touch chip [BS814A](https://so.szlcsc.com/global.html?k=BS814A).
* This project is a sample project of the [Solution Verification Module Collection Order](https://oshwhub.com/rewards/f4bbab6365034e80aadb8f8ebf77c846) of the [Lichuang EDA Open Source Hardware Platform](https://oshwhub.com/).

All the output pins of the touch keys of BS814A-1 are NMOS type and have built-in pull-up resistors, so no external resistors are required. When no key touch action occurs, the logic level is high. When the chip detects that the touch key is pressed, its corresponding output port will output a low potential.

BS814A-2 is equipped with a ~~~~ serial interface, allowing simple communication with external devices. When the touch chip detects that the touch key is pressed, it will output a low level at the Data pin to wake up the host. After receiving the low level, the host outputs a clock signal from the Clock pin and reads back the key value from the Data pin. When a low level
is input to the Clock pin, the touch chip prepares the data. After the Clock pin sends a high level, the host reads the data from the Data line. Each data is read in a group of 8 clock signals. The key value can also be read directly in a polling manner without waiting for the Start bit.
When the data is read incorrectly, it takes about 6ms to read it again.