UART data transmit DMA problems
Hello,
i am working on a application where i try to measure a motor speed and current, and then send the data to the PC using serial uart.
The device used is a STM32F427
For controlling the motor i used a timer1 6pwm channels triggered by timer2 hall xor event.
The motor runs with no problems.
For uart transition i use UART3 with DMA TX
- Timer2 CC1 IRQ event occurs at every change in the state of the 3 hall sensors, here i store the CNT value to the rpm variable.
- in the main program loop i check if a previously DMA transfer has ben made ( flag = 0?)
- if yes, then i set the flag , and read the current value and store to a variable called current , and convert the data to string using sprintf in the following format 1234,5678\r\n (11 chars in lenght)
- after i converted the data, i enable the DMA USART TX request
- when the DMA TC completes, i copy the previously converted data to a temporary string buffer for sending out to the USART, afterwards the DMA TX is disabled
The problem i am facing is when displaying the data on the PC i get very often garbage data.
I have attached a small terminal data showing with red marking the garbage, and a simplified version of the code
How to overcome this?
char tmp[2]='''';
char Buffer[20]='''';
uint16_t buflen=11;
void DMA1_Stream3_IRQHandler(void){ if (DMA_GetITStatus(DMA1_Stream3, DMA_IT_TCIF3)) { DMA_ClearITPendingBit(DMA1_Stream3, DMA_IT_TCIF3);USART_DMACmd(USART3, USART_DMAReq_Tx, DISABLE); // disable DMA USART TX request
for(int k=0; k<buflen; k++)
tmp[k]=Buffer[k];
flag=0; // set }}void TIM2_IRQHandler(){ if (TIM_GetITStatus(TIM2, TIM_IT_CC1) != RESET) {TIM_ClearITPendingBit(TIM2, TIM_IT_CC1);
rpm = calculate_rpm(); // store the time between hall sensor state change
}
}
int main(void){
init_usart_with_dma();
while(1){
if(flag==0){
flag=1; // set the DMA flag// read external current sensor
GPIOA->BSRRH = GPIO_Pin_3; // set CS Low SPI1->DR = 0x00;/// write data to be transmitted to the SPI data register while( !(SPI1->SR & SPI_I2S_FLAG_RXNE) ); // wait until receive complete while( SPI1->SR & SPI_I2S_FLAG_BSY ); // wait until SPI is not busy anymore current =SPI1->DR; // return received data from SPI data register GPIOA->BSRRL = GPIO_Pin_3; // set CS Highsprintf(Buffer,''%04d,%04d\r\n'',current,rpm); // 12chars - convert uint to string
USART_DMACmd(USART3, USART_DMAReq_Tx, ENABLE); // re-enable DMA USART TX request
}
}
}
void init_usart_with_dma(void){ DMA_InitTypeDef DMA_InitStructure; USART_InitTypeDef USART_InitStructure; GPIO_InitTypeDef GPIO_InitStruct2; // USART 3 TX - is tied to DMA1 Stream3//PB 10 - TX
//PB 11 - RXGPIO_InitStruct2.GPIO_Pin = GPIO_Pin_10 | GPIO_Pin_11; // Pins 10 (TX) and 11 (RX) are used
GPIO_InitStruct2.GPIO_Mode = GPIO_Mode_AF; // the pins are configured as alternate function so the USART peripheral has access to them GPIO_InitStruct2.GPIO_Speed = GPIO_Speed_50MHz; // this defines the IO speed and has nothing to do with the baudrate! GPIO_InitStruct2.GPIO_OType = GPIO_OType_PP; // this defines the output type as push pull mode (as opposed to open drain) GPIO_InitStruct2.GPIO_PuPd = GPIO_PuPd_UP; // this activates the pullup resistors on the IO pins GPIO_Init(GPIOB, &GPIO_InitStruct2);GPIO_PinAFConfig(GPIOB, GPIO_PinSource10, GPIO_AF_USART3); //
GPIO_PinAFConfig(GPIOB, GPIO_PinSource11, GPIO_AF_USART3);RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);USART_InitStructure.USART_BaudRate = 38400;// 115200;
USART_InitStructure.USART_WordLength = USART_WordLength_8b; USART_InitStructure.USART_StopBits = USART_StopBits_1; USART_InitStructure.USART_Parity = USART_Parity_No; USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; USART_Init(USART3, &USART_InitStructure); USART_ITConfig(USART3, USART_IT_RXNE, ENABLE); USART_Cmd(USART3, ENABLE); //++++++++++++++++ SETUP DMA ++++++++++++++++++++++++//NVIC_InitStructure.NVIC_IRQChannel = DMA1_Stream3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure);DMA_DeInit(DMA1_Stream3);DMA_InitStructure.DMA_Channel = DMA_Channel_4;DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral; // TransmitDMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)tmp;DMA_InitStructure.DMA_BufferSize = (uint16_t)sizeof(tmp) - 1;DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART3->DR;DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;DMA_InitStructure.DMA_Priority = DMA_Priority_High;DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Enable;DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;DMA_Init(DMA1_Stream3, &DMA_InitStructure);// Enable the USART Tx DMA request
USART_DMACmd(USART3, USART_DMAReq_Tx, ENABLE);// Enable DMA Stream Transfer Complete interrupt
DMA_ITConfig(DMA1_Stream3, DMA_IT_TC, ENABLE);// Enable the DMA RX Stream
DMA_Cmd(DMA1_Stream3, ENABLE);}