AD acquisition system based on STM8S

The STM8S series has up to 16 AD channels, depending on the package size. Many pins have multiplexing functions, which are similar to ordinary 51, and for IO ports with multiplexing functions, they can be used directly without any multiplexing settings. In addition, the multiplexing function can also remap the pins, which requires mapping configuration in the option bytes. For the pins to be configured as AD acquisition ports, they must be set to floating input mode, not any other output mode, which will seriously interfere with the measurement of input voltage. Due to the use of small packages, there is no special reference voltage, and the internal is directly connected to the power supply end. Therefore, the instability of the power supply end is the instability of the reference voltage, which will directly lead to the instability and jump of the conversion value. There is a flashing light in the design at the beginning, which causes a small fluctuation in the power supply and affects the conversion value. After the flashing light is cancelled, the conversion value stabilizes. Since the large voltage is measured by the voltage divider resistor, it is inevitable that the conversion value is inaccurate due to the error of the voltage divider resistor. The error can be eliminated by collecting the reference voltage to determine the actual voltage divider ratio of the voltage divider resistor, but the error caused by the acquisition error will become larger after amplification. The instability of the input signal can be corrected by adding an RC filter circuit, or by filtering in the software. By removing the extreme value and averaging after multiple sampling, the collected value tends to be stable. In this design, there is a 1-unit jump when the final value is displayed. In order to make the value look stable, the value is updated only when the difference between the current data and the previous data is greater than 1 unit, so that the currently collected data remains unchanged.

In the programming of the host computer, since the program is triggered by events, the relationship between each object and the event must be properly handled. The transmission of information must be well organized, otherwise it will affect the entire system.