STM32F407VG using USART with DMA

[mk61]

Posted on March 31, 2017 at 07:13

Hi everyone,

I wanted to move a data array(source) to another data array(destination) using USART2 and I wanted to move datas to usart2 and from usart2 by using DMA1. I connect the tx pin to rx pin and it worked. The thing confused me is when I disconnected pins somehow some of the datas were able to go to destination array.

My code is below. Can you explain me what is going on? 

&sharpinclude <stm32f4xx.h>

int sayac = 0;int main(){ USART_InitTypeDef USART_InitStructure; GPIO_InitTypeDef GPIO_InitStructure; DMA_InitTypeDef DMA_InitStructure; uint8_t source[500] = 'Hello World

Hello World Hello World Hello World Hello World Hello WorldHello WorldHello WorldHello World Hello World Hello World Hello WorldHello WorldHello WorldHello WorldHello World Hello World Hello World Hello World Hello World Hello World etc..

'; uint8_t destination[500] = {0}; RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1,ENABLE); RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2,ENABLE); RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD,ENABLE); //GPIO Initialisation for USART GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_6; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz; GPIO_Init(GPIOD,&GPIO_InitStructure); GPIO_PinAFConfig(GPIOD,GPIO_PinSource5,GPIO_AF_USART2); GPIO_PinAFConfig(GPIOD,GPIO_PinSource6,GPIO_AF_USART2); //USART Initialisation USART_InitStructure.USART_BaudRate = 9600; USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; USART_InitStructure.USART_Parity = USART_Parity_No; USART_InitStructure.USART_StopBits = USART_StopBits_1; USART_InitStructure.USART_WordLength = USART_WordLength_8b; USART_Init(USART2,&USART_InitStructure); USART_Cmd(USART2,ENABLE); //DMA Stream6 Initialisation for USART Tx DMA_DeInit(DMA1_Stream6); while(DMA_GetCmdStatus(DMA1_Stream6) != DISABLE); DMA_InitStructure.DMA_Channel = DMA_Channel_4; //channel of the stream DMA_InitStructure.DMA_Priority = DMA_Priority_High; //select priority of the stream DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)source; //address of source DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART2->DR; //address of peripheral DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral; //Direction of the transfer DMA_InitStructure.DMA_BufferSize = sizeof(source); //amount of data to be sent DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //Enable incremantation of memory address DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //Disable incremantation of peripheral address DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; //verinin boyutu DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; //verinin boyutu DMA_InitStructure.DMA_Mode = DMA_Mode_Normal; //Stream is disabled when Transfer finishes DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable; DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full; //Fifo disable oldugu i�in �ok �nemli degil DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single; //minumum burst miktar1 yaz1lmazsa olmuyor DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single; //minumum burst miktar1 yaz1lmazsa olmuyor DMA_Init(DMA1_Stream6,&DMA_InitStructure); //DMA Stream5 Initialisation for USART Rx DMA_DeInit(DMA1_Stream5); while(DMA_GetCmdStatus(DMA1_Stream5) != DISABLE); DMA_InitStructure.DMA_Channel = DMA_Channel_4; //channel of the stream DMA_InitStructure.DMA_Priority = DMA_Priority_High; //select priority of the stream DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)destination; //address of source DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART2->DR; //address of peripheral DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory; //Direction of the transfer DMA_InitStructure.DMA_BufferSize = sizeof(destination); //amount of data to be sent DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //Enable incremantation of memory address DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //Disable incremantation of peripheral address DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; //verinin boyutu DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; //verinin boyutu DMA_InitStructure.DMA_Mode = DMA_Mode_Normal; //Stream is disabled when Transfer finishes DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable; DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full; //Fifo disable oldugu i�in �ok �nemli degil DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single; //minumum burst miktar1 yaz1lmazsa olmuyor DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single; //minumum burst miktar1 yaz1lmazsa olmuyor DMA_Init(DMA1_Stream5,&DMA_InitStructure);

USART_ClearFlag(USART2,USART_FLAG_RXNE);

USART_ClearFlag(USART2,USART_FLAG_TXE); USART_DMACmd(USART2,USART_DMAReq_Rx,ENABLE); USART_DMACmd(USART2,USART_DMAReq_Tx,ENABLE);

DMA_Cmd(DMA1_Stream6,ENABLE);

DMA_Cmd(DMA1_Stream5,ENABLE); while(1) { }}#stm32f407vg-using-usart-with-dma*

[Tesla DeLorean]

Posted on March 31, 2017 at 12:53

It is not a memory cell,  the peripherals has two different registers at the same address,  but the one being written is not the same one that is being read. Look at a functional diagram in the reference manual. 

[mk61]

Posted on March 31, 2017 at 14:23

I got it now. Thank you.