/**
  ******************************************************************************
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Copyright (C) Shanghai Eastsoft Microelectronics Co., Ltd. ALL rights reserved.
  *******************************************************************************
  */

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Version history:
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2019-07-02	V1.00	AE TEAM
2022-07-17	V1.01	AE TEAM
1.适配ES-PDS-ES32F3696LX开发板

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Demo introduction:
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本示例功能：使用DMA的乒乓模式交替发送字符串。

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测试环境:
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测试用板：
ES-PDS-ES32F3696LX-V1.0

辅助工具：


辅助软件：
串口调试助手


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测试步骤：
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1) 编译工程，编译通过后将程序下载到目标芯片；
2) 将程序配置的TX/RX对应的引脚分别连接ES-LinkII-OB的RX/TX；
3) 打开串口调试助手软件，配置串口参数(115200bps-8-1-N)后打开ES-LinkII-OB对应的串口；
4) 在线调试，UART_TX持续不断的向串口调试助手输出:
task1:hello world!
task2:hello world!
task3:hello world!
task4:hello world!
task5:hello world!

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注意：
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System clock:
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外部HOSC 12MHz 3分频后PLL倍频到72MHz.

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Pin connection: 
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UART2_TX ---- PE2[GPIO_FUNC_3]
UART2_RX ---- PE3[GPIO_FUNC_3]
