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                                样例使用说明
                             Sample Description
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功能描述：
此样例演示了ADC的Vrefint功能，通过Vrefint的值，可以反推出MCU的供电电压值。

Function descriptions:
This example demonstrates the Vrefint function of ADC. By using the value of
Vrefint, the power supply voltage value of MCU can be inferred
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测试环境：
测试用板：PY32E407_STK
MDK版本： 5.28
IAR版本： 9.20
GCC版本：GNU Arm Embedded Toolchain 10.3-2021.10

Test environment:
Test board: PY32E407_STK
MDK Version: 5.28
IAR Version: 9.20
GCC Version: GNU Arm Embedded Toolchain 10.3-2021.10
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使用步骤：
1. 编译并下载程序；
2. 串口每隔1s打印一次VCC的电压值；

Example execution steps:
1. Compile and download the program;
2. The serial port prints the voltage value of VCC every 1 second;

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注意事项：
1. PY32E407-START V2.0 上L2/C38必须焊接.
2. 通过USB转TTL模块连接PC与STK板,STK板与USB转TTL模块的连线方式如下；
STK板         USB转TTL模块
PA0(TX)  -->  RX
GND      -->  GND
UART配置为波特率9600。

Notes:
1. The L2/C38 on PY32E407-START V2.0 must be welded.
2. Connect the PC to the STK board through the USB to TTL module, and the connection
method between the STK board and the USB to TTL module is as follows:
STK board     USB to TTL module
PA0(TX)  -->  RX
GND      -->  GND
UART is configured as BaudRate 9600.
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