Voltmeter and Ammeter

This project replicates the LCSC CW32 digital voltmeter and ammeter expansion board. Based on the original project, the plug-in components were changed to 0603 surface-mount components, and the digital tube was replaced with
a 0.96-inch I2C OLED. Function Introduction
  : 1.1 Voltage 0-30V ADC measurement;
  1.2 Current ADC measurement;
  1.3 Calibration function
      : Defines 5 working modes; K1 key is used to switch modes; K2 key is used to set parameters and save to Flash; K3 key is the return key.

Mode 0: Displays voltage and current values.
Mode 1: 5V voltage calibration setting, the previous line displays the identifier: V.05, and the next line displays the value collected by the ADC after calibrating 5V.
Mode 2: 15V voltage calibration setting, the previous line displays the identifier: V.15, and the next line displays the value collected by the ADC after calibrating 15V.
Mode 3: 0.5A current calibration setting, the previous line displays the identifier: A.0.5, and the next line displays the value collected by the ADC after calibrating 0.5A.
Mode 4: 1.5A current calibration setting, the previous line displays the identifier: A.1.5, and the next line displays the value collected by the ADC after calibrating 1.5A.

II. Hardware Design
  2.1 Schematic Design
    2.1.1 Power Supply Circuit
    LDO (Low Dropout Linear Regulator) Selection This project uses an LDO as the power supply. Considering that most actual voltmeter products are used in industrial scenarios with 24V or 36V power supply, this project selected the SE8550K2 with a maximum input voltage of up to 40V as the power supply. The main reason for not using a DC-DC step-down circuit to handle large voltage differences in this project is to avoid introducing DC-DC ripple interference during the design process; a secondary reason is to reduce project costs.
 
    2.1.2 The main control circuit
        uses the LCSC-Divin Star CW32F030C8T6 development board as the core board.
 
  2.1.3 Voltage sampling circuit .
 
    2.1.4 Current sampling circuit .  
III. Software design
  details are in the attached voltage.rar file.
 
IV. Demonstration video.