灵动微｜基于MM32L0130的LPUART应用（2）
灵动微｜基于MM32L0130的LPUART应用（2）LPUART（Low power universal asynchronous receiver transmitter，低功耗通用异步收发器），相比标准的UART，其功耗极低，支持在低功耗模式下运行，并且可以将MCU从低功耗模式唤醒。上期介绍了MM32全新低功耗系列MM32L0130的LPUART外设，并实现了基本UART收发通信和使用LPUART唤醒MCU。本期介绍LPUART的高级应用，实现DMA收发实验、使用数据匹配寄存器匹配到指定字符后唤醒MCU。
1LPUART使用DMALPUART可以使用DMA来搬运数据，实现无需CPU参与的快速自动数据传输。硬件发出DMA请求与对应的DMA通道直连，也可以通过软件配置寄存器的方式触发DMA通道请求。LPUART的控制寄存器有对应的DMA使能位，如下图所示：
1.1DMA中断DMA的每个通道都有三种中断事件标志：DMA半传输、DMA传输完成和DMA传输出错。各通道单独的中断请求由这3种事件标志逻辑或起来。可以配置寄存器的对应位来使能这些中断：
1.2LPUART使用DMA的配置步骤1根据基本UART配置步骤配置LPUART2使能LPUEN的DMAR与DMAT位激活DMA模式3使能DMA时钟4发送需要配置DMA的源地址（存储器地址）和目的地址（LPUTXD），传输的数据量以及DMA通道5配置完发送后，只要TXFIFO为空，就会请求DMA发送6接收需要配置DMA的源地址（LPURXD）和目的地址（存储器地址），传输的数据量以及DMA通道7配置完接收后，只要RXFIFO有数据，即不为空，就会请求DMA接收
1.3功能代码实现下面例程实现了使用DMA发送和接收LPUART数据，发送和接收完成后进入中断，例程在基本UART收发实验的基础上完成。a.申请例程所用到的TX和RX缓存、TX和RX完成标志：uint8_t TX_Buffer, RX_Buffer;
uint8_t TX_Complete = 0, RX_Complete = 0;
b.配置NVIC：NVIC_InitTypeDefNVIC_InitStruct;
NVIC_InitStruct.NVIC_IRQChannel = DMA1_Channel2_3_IRQn;
NVIC_InitStruct.NVIC_IRQChannelPriority = 2;
NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStruct);
c.配置DMA通道2为LPUART_TX：void LPUART_DMA_TX_Init(void)
{
DMA_InitTypeDef DMA_InitStruct;
RCC_DMA_ClockCmd(DMA1, ENABLE);
DMA_DeInit(DMA1_Channel2);
DMA_StructInit(&DMA_InitStruct);
//DMA transfer peripheral address
DMA_InitStruct.DMA_PeripheralBaseAddr = (uint32_t)&LPUART1->LPUTXD;
//DMA transfer memory address
DMA_InitStruct.DMA_MemoryBaseAddr = (uint32_t)TX_Buffer;
//DMA transfer direction from peripheral to memory
DMA_InitStruct.DMA_DIR = DMA_DIR_PeripheralDST;
//DMA cache size
DMA_InitStruct.DMA_BufferSize = 16;
//The peripheral address is forbidden to move backward
DMA_InitStruct.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
//The memory address is shifted backward
DMA_InitStruct.DMA_MemoryInc = DMA_MemoryInc_Enable;
//Define the peripheral data width to 8 bits
DMA_InitStruct.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStruct.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStruct.DMA_Mode = DMA_Mode_Normal;
DMA_InitStruct.DMA_Priority = DMA_Priority_Medium;
//M2M mode is disabled
DMA_InitStruct.DMA_M2M = DMA_M2M_Disable;
DMA_InitStruct.DMA_Auto_reload = DMA_Auto_Reload_Disable;
DMA_Init(DMA1_Channel2, &DMA_InitStruct);
DMA_SetChannelMuxSource(DMA1_Channel2, DMA1_MUX_LPUART1_TX);
//Enable LPUART_DMA1_Channel Transfer complete interrupt
DMA_ITConfig(DMA1_Channel2, DMA_IT_TC, ENABLE);
LPUART_TX_DMACmd(LPUART1, ENABLE);
while((LPUART1->LPUEN & LPUART_LPUEN_DMAT) == 0);
//LPUART_DMA1_Channel enable
DMA_Cmd(DMA1_Channel2, ENABLE);
}
d.配置DMA通道3为LPUART_RX：void LPUART_DMA_RX_Init(void)
{
DMA_InitTypeDef DMA_InitStruct;
RCC_DMA_ClockCmd(DMA1, ENABLE);
DMA_DeInit(DMA1_Channel3);
DMA_StructInit(&DMA_InitStruct);
//DMA transfer peripheral address
DMA_InitStruct.DMA_PeripheralBaseAddr = (uint32_t)&LPUART1->LPURXD;
//DMA transfer memory address
DMA_InitStruct.DMA_MemoryBaseAddr = (uint32_t)RX_Buffer;
//DMA transfer direction from peripheral to memory
DMA_InitStruct.DMA_DIR = DMA_DIR_PeripheralSRC;
//DMA cache size
DMA_InitStruct.DMA_BufferSize = 16;
//The peripheral address is forbidden to move backward
DMA_InitStruct.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
//The memory address is shifted backward
DMA_InitStruct.DMA_MemoryInc = DMA_MemoryInc_Enable;
//Define the peripheral data width to 8 bits
DMA_InitStruct.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStruct.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStruct.DMA_Mode = DMA_Mode_Normal;
DMA_InitStruct.DMA_Priority = DMA_Priority_Medium;
//M2M mode is disabled
DMA_InitStruct.DMA_M2M = DMA_M2M_Disable;
DMA_InitStruct.DMA_Auto_reload = DMA_Auto_Reload_Disable;
DMA_Init(DMA1_Channel3, &DMA_InitStruct);
DMA_SetChannelMuxSource(DMA1_Channel3, DMA1_MUX_LPUART1_RX);
//Enable LPUART_DMA1_Channel Transfer complete interrupt
DMA_ITConfig(DMA1_Channel3, DMA_IT_TC, ENABLE);
LPUART_RX_DMACmd(LPUART1, ENABLE);
while((LPUART1->LPUEN & LPUART_LPUEN_DMAR) == 0);
//LPUART_DMA1_Channel enable
DMA_Cmd(DMA1_Channel3, ENABLE);
}
e.编写中断服务函数：void DMA1_Channel2_3_IRQHandler(void)
{
if(DMA_GetITStatus(DMA1_IT_TC2))
{
DMA_ClearITPendingBit(DMA1_IT_TC2);
TX_Complete = 1;
}
if(DMA_GetITStatus(DMA1_IT_TC3))
{
DMA_ClearITPendingBit(DMA1_IT_TC3);
RX_Complete = 1;
}
}
f.编写实验样例：void LPUART_RxTx_DMA_Test(void)
{
uint8_t i;
for(i = 0; i < 16; i++)
{
TX_Buffer = i;
}
LPUART_DMA_TX_Init();
LPUART_DMA_RX_Init();
while(1)
{
if(TX_Complete == 1)
{
TX_Complete = 0;
DMA1_Channel3->CMAR = (uint32_t)RX_Buffer;
DMA1_Channel3->CNDTR = 16;
DMA_Cmd(DMA1_Channel3, ENABLE);
}
if(RX_Complete == 1)
{
RX_Complete = 0;
memcpy((void *)TX_Buffer, (void *)RX_Buffer, 16);
DMA1_Channel2->CMAR = (uint32_t)TX_Buffer;
DMA1_Channel2->CNDTR = 16;
DMA_Cmd(DMA1_Channel2, ENABLE);
}
}
}
g.在main函数中配置好LPUART和DMA后，调用实验函数LPUART_RxTx_DMA_Test，可以得到如下结果：
2使用数据匹配寄存器匹配到指定字符后唤醒MCU为进一步降低系统功耗，MM32L0130系列的LPUART提供了一种接收到指定字符才能唤醒低功耗状态的MCU的功能。用于唤醒的指定字符，由数据匹配寄存器确定：
2.1接收中断配置寄存器可以通过LPUART的LPUCON.RXEV寄存器配置唤醒事件为START位、一帧接收完成、一帧数据匹配或者RXD下降沿唤醒。
2.2功能代码实现匹配指定字符唤醒MCU功能，需要在上期讲解的LPUART唤醒低功耗模式中的MCU基础上修改中断事件配置、指定唤醒字符，具体代码如下：a.配置LPUART接收中断事件为接收数据匹配成功：LPUART_InitTypeDef init_struct;
init_struct.LPUART_Clock_Source = 0;
init_struct.LPUART_BaudRate = LPUART_Baudrate_9600;
init_struct.LPUART_WordLength = LPUART_WordLength_8b;
init_struct.LPUART_StopBits = LPUART_StopBits_1;
init_struct.LPUART_Parity = LPUART_Parity_No;
init_struct.LPUART_MDU_Value = 0x952;
init_struct.LPUART_NEDET_Source = LPUART_NegativeDectect_Source2;
init_struct.LPUART_RecvEventCfg = LPUART_RecvEvent_RecvData_Mactched;
LPUART_Init(LPUART1, &init_struct);
b.配置特定的唤醒字符：LPUART_SetMatchData(LPUART1, ‘5’); //指定字符’5’为唤醒字符
c.编写中断服务程序，判断接收匹配事件并清除标志：void LPUART1_IRQHandler()
{
if(LPUART_GetFlagStatus(LPUART1, LPUART_LPUSTA_START))
{
LPUART_ClearFlagStatus(LPUART1, LPUART_LPUSTA_START);
}
if(LPUART_GetFlagStatus(LPUART1, LPUART_LPUSTA_MATCH))
{//判断接收中断匹配事件
LPUART_ClearFlagStatus(LPUART1, LPUART_LPUSTA_MATCH);
}
if(LPUART_GetITStatus(LPUART1, LPUART_LPUIF_RXIF) == SET) {
LPUART_ClearITPendingBit(LPUART1, LPUART_LPUIF_RXIF);
rxDataBuf = LPUART_ReceiveData(LPUART1);
if(++cnt >= 10)
cnt_flag = 1;
}
EXTI_ClearITPendingBit(EXTI_Line22);
}
d.编写试验样例：void LPUART_Wakeup_Test(void)
{
uint8_t temp, i;
char string1[] = "LPUART wakeup mcu test!\r\n";
char string2[] = "mcu stop!\r\n";
char string3[] = "mcu wakeup!\r\n";
for(i = 0; i < strlen(string1); i++)
{
Output_Byte(LPUART1, string1);
}
DELAY_Ms(20);
for(i = 0; i < strlen(string2); i++)
{
Output_Byte(LPUART1, string2);
}
PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);//休眠
for(i = 0; i < strlen(string3); i++)
{
Output_Byte(LPUART1, string3);
}
while(1)
{
}
}
e.在main函数配置好LPUART后，调用实验函数LPUART_Wakeup_Test，可以得到如下结果：
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