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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模块的Vrefbuf功能，利用vrefbuf作为基准去采样通道的值，并转换成电压
通过串口打印出来。

Function descriptions:
This example demonstrates the Vrefbuf function of the ADC module, which uses 
Vrefbuf as the reference to sample channel values and convert them into voltage
Print it out through the serial port.
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测试环境：
测试用板：PY32MD420_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: PY32MD420_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打印一次通道4的电压值。

Example execution steps:
1. Compile and download the program;
2. The serial port prints the voltage value of channel 4 every 1 second;
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注意事项：
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:
@PrintfConfigStart
STK板        USB转TTL模块
PA02(TX)  -->  RX
PA03(RX)  -->  TX
GND       -->  GND
UART配置为波特率115200，数据位8，停止位1，校验位None
@PrintfConfigEnd

Notes:
Connect PC and STK board through USB to TTL module and the connection method
is as follows
@PrintfConfigStart
STK board    USB to TTL moudle
PA02(TX)  -->  RX
PA03(RX)  -->  TX
GND      -->  GND
UART is configured as BaudRate 115200, data bit 8, stop bit 1, and parity None.
@PrintfConfigEnd
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