STM32F103T8 usart2 corrupted data

mikaeleg · ‎2011-09-27

Posted on September 28, 2011 at 08:12

Hi,

Im trying to get the usart2 working but for some reason I get random corrupted data when I send message to the STM32F103T8. I can send messages from the STM32 to the computer without any corrupted bytes but not the other way around.

The usart2 is piping the received messages to a DMA. I've activated the usart2 in the following way:

DMA_DeInit(DMA1_Channel6);

DMA_StructInit(&DMA_InitStructure);

DMA_InitStructure.DMA_PeripheralBaseAddr = USART2_DR_Base;

DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)gRXBuf2; //Define in usart2.h

DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;

DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;

DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;

DMA_InitStructure.DMA_BufferSize = RX_BUF_SIZE2; //Define in usart2.h

DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;

DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;

DMA_Init( DMA1_Channel6, &DMA_InitStructure );

USART_InitStructure2.USART_BaudRate = 4800;

USART_InitStructure2.USART_WordLength = USART_WordLength_8b;

USART_InitStructure2.USART_StopBits = USART_StopBits_1;

USART_InitStructure2.USART_Parity = USART_Parity_No;

USART_InitStructure2.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

USART_InitStructure2.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

/* Configure USART2 */

USART_Init(USART2, &USART_InitStructure2);

/* Enable USART2 Receive and Transmit interrupts */

USART_ITConfig(USART2, USART_IT_TC, ENABLE);

// Enable USART2 Receive DMA requests

USART_DMACmd(USART2, USART_DMAReq_Rx, ENABLE);

// Enable DMA1 USART RX channel

DMA_Cmd(DMA1_Channel6, ENABLE);

// Enable USART2

USART_Cmd(USART2, ENABLE);

I have also enabled the usart2 clock as following:

RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);

And finally enabled the usart2 interrupt:

NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

I've done a simple program which checks when new data have been added to the DMA memory where the received data is and send the exact same data back to the computer.

Then i connect to the STM32 with the windows xp hyperterminal and sends some chars.

For example if i send GPGGA, I might get back something like GP=GA or even worse like G?G, where some chars is ''.

Does anyone have any idea what might be wrong? I would really appriciate the help.

Cheers

Mike

#stm32-stm32f103-usart-corrupted

Andrew Neil · ‎2011-09-28

Posted on September 28, 2011 at 11:09

''Does anyone have any idea what might be wrong?''

The usual reason is that your baud rate is not (quite) correct - have you checked with a scope to see exactly what baudrate the STM32 is actually using?

Is the STM32 reporting any Framing errors?

mikaeleg · ‎2011-09-28

Posted on September 28, 2011 at 13:25

Thank you for such a fast answer.

Ive checked the framing error but it is never set, and I have also tested different baudrate but the same corruption occurred.

I have more or less the same code for the USART1 but with dma channel 5 and it works perfectly.

I recently discovered something which might be the problem.

I gave the DMA the memory address for a buffer gRXBuf2 which basicly is defined as:

volatile char gRXBuf2[RX_BUF_SIZE2];

The RX_BUF_SIZE2 is defined as 30. I belive that when the usart2 receives data it automaticly goes into the DMA memory, in this case the gRXBuf2, so for example if I send the message ''GPGGA'' then the buffer should look like:

gRXBuf2[0] = 'G'

gRXBuf2[

1

] = '

P

'

gRXBuf2[

2

] = 'G'

gRXBuf2[

3

] = 'G'

gRXBuf2[

4

] = '

A

'

So I tried to send the previous value in the buffer also.

Something like this:

USART2_transmit(''This: '', 6);

USART2_transmit((char*)&gRXBuf2[gRXBufPtr2], 1);

USART2_transmit(''\r\n'', 2);

if(gRXBufPtr2>0)

{

USART2_transmit(''Prev: '', 6);

USART2_transmit((char*)&gRXBuf2[gRXBufPtr2-1], 1);

USART2_transmit(''\r\n'', 2);

}

And what I got when i only send a's is the following:

This: ê

This: a

Prev: �?

This: <

Prev: �?

This:

Prev: <

This:

Tesla DeLorean · ‎2011-09-28

Posted on September 28, 2011 at 14:16

DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;

DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;

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mikaeleg · ‎2011-09-28

Posted on September 28, 2011 at 14:52

I tried added:

DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;

DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;

but still same corruption of data.

Tesla DeLorean · ‎2011-09-28

Posted on September 28, 2011 at 15:42

Does it work with polled (ie not IRQ or DMA) receive on the same USART?

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mikaeleg · ‎2011-09-29

Posted on September 29, 2011 at 09:09

Hi again,

Im sorry for the late answer but i tried what you said .

I did a simple program like:

while(1)

{

/* Loop until the USARTz Receive Data Register is not empty */

while(USART_GetFlagStatus(USART2, USART_FLAG_RXNE) == RESET)

{

}

gRXBuf2[gRXBufPtr2++] = (USART_ReceiveData(USART2) & 0x7F);

USART2_transmit((char*)&gRXBuf2[gRXBufPtr2-1], 1);

if( gRXBufPtr2 == RX_BUF_SIZE2 )

{

gRXBufPtr2 = 0;

}

and it worked perfectly, so i assume that something is disturbing the dma channel?

mikaeleg · ‎2011-10-03

Posted on October 04, 2011 at 08:26

Just wanted to update this thread as I found the problem.

The problem was that I were on the limits of the memory on the MCU.

So after I reduced some buffers everything worked perfectly.

When you run out of memory, strange things start to happen.

hassankasim84 · ‎2012-06-12

Posted on June 12, 2012 at 14:17

Hii

I had the same problem that you had, can you please tell me how to solve that, Actually I had (chr6dm) module which contain ARM Processor and in this module they used USART1 and now I need to use USART2 for another sensor, I think you also have the same module right ????

hassankasim84 · ‎2012-06-12

Posted on June 12, 2012 at 14:21

I had forgot something what is the (

USART2_DR_Base

) that you used????