CW32 Voltage and Current Meter

I. Project Design
This project is a digital voltmeter and ammeter designed based on the LCSC CW32 development board. The hardware selection followed the documentation and videos in the LCSC training camp step by step.
A physical image is shown below.
II. Project Functionality

Supports 0-30V voltage ADC measurement with a display accuracy of 0.1V/0.01V; supports 0-3V precise ADC measurement with a display accuracy of 0.01V;
supports 0-3A current ADC measurement with a display accuracy of 0.01A;
can detect the voltage and current values ​​of the tested circuit in real time ;
can simultaneously detect the voltage and current values ​​of the tested circuit.

III. Hardware Design (Partial)
Due to the large number of circuits, only a portion is shown here. Please refer to the schematic diagram for details. For a more detailed and thorough understanding, please refer to the official "CW32 Digital Voltmeter and Ammeter Training Camp Project Tutorial Document" and "[Step-by-Step Guide to Making a Voltmeter and Ammeter]".
1. Power Supply Circuit
LDO (Low Dropout Linear Regulator) Selection:
This project uses an LDO as the power supply. Considering that most voltmeter products are used in industrial scenarios with 24V or 36V power supplies, the SE8550K2 with a maximum input voltage of up to 40V was selected as the power supply. The main reason for not using a DC-DC buck converter to handle the large voltage drop is to avoid introducing DC-DC ripple interference during the design process; a secondary reason is to reduce project costs.
2. Voltage Sampling Circuit:
The voltage divider resistors in this project are designed to be 220K+10K, therefore the voltage division ratio is 22:1 (ADC_IN11).
Voltage divider resistor selection:

The maximum value of the measured voltage is 30V for safety reasons (the actual maximum display value can be 99.9V or 100V).
ADC reference voltage: In this project, it is 1.5V, which can be configured through the program.
Power consumption: To reduce the power consumption of the sampling circuit, the low-side resistor (R7) is usually selected as 10K based on experience.

3. Current Sampling Circuit:
This project uses a low-side current sampling circuit for current detection. The low-side of the sampling circuit shares a common ground with the development board's meter interface. In the current wiring port circuit on the right side of the image, CN2 pins 1 and 2 are connected to TA and TI+ respectively (not shown on the schematic, but present on the PCB).
4. Digital Tube Display:
This project uses two 0.28-inch three-digit common-cathode digital tubes as display devices. Compared to displays, digital tubes offer better visibility in complex environments. Depending on the specific needs of the application environment, smaller current-limiting resistors can be used to achieve higher brightness. Furthermore, digital tubes possess better mechanical properties and are not as easily damaged by external forces as displays. They are widely used in industrial applications requiring stability and reliability. From a development board learning perspective, this makes it easier to purposefully learn about electronic measurement principles and related development.
Demonstration videos and code are attached.