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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I2C通过轮询方式进行通讯，主机先向从机发送15byte数据，然后再接收从机
发送的15byte数据,主机、从机接收数据成功后，主机和从机板上的小灯处于“常亮”状态。

Function descriptions:
This sample demonstrates that I2C communicates with polling mode, the host first
sends 15byte data to the slave, and then receives 15byte data from the slave.
After the host and slave successfully receive data, the LEDs on the host and 
slave board are in the state of "steady on".
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测试环境：
测试用板：PY32L020_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: PY32L020_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. 编译下载程序到MCU，并运行
2. 先复位从机，然后再复位主机
3. 复位完成后，按下主机user按键，主从开始通讯
4. 观察主从机的LED灯，当主机和从机LED灯由常暗转为常亮状态，则表明主机、从机收发数
据成功；当主机或从机LED灯处于闪烁状态，则表明主机、从机收发数据失败。

Example execution steps:
1. Compile and download the program and run it
2. Reset the slave and then the master
3. After the reset is complete, press the user button of the host to start
communication between the master and slave
4. Observe the LED of the master and slave. When the LED lights of the master 
and slave turn from off to steady on, it indicates that the master and slave 
receive and send data successfully; When the LED of the host or slave is 
blinking,it indicates that the host or slave fails to receive and or data.
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注意事项：
PB3     ------> I2C_SCL
PB4     ------> I2C_SDA
主机程序为I2C_TwoBoard_CommunicationMaster_Polling_Init
从机程序为I2C_TwoBoard_CommunicationSlave_IT_Init
如需修改速率，直接修改I2C_SPEEDCLOCK即可

Notes:
PB3     ------> I2C_SCL
PB4     ------> I2C_SDA
Master program name:I2C_TwoBoard_CommunicationMaster_Polling_Init
Slave program name:I2C_TwoBoard_CommunicationSlave_IT_Init
I2C_SPEEDCLOCK can be modified to change the communication frequency
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