USART2 - I2C1 problem in STM32F1

[Martin.Sergio]

Posted on March 14, 2014 at 14:28

When I send data to the USART2 it's well received BUT after that the last data character keeps being received until filling up my reception buffer. Note that in the same application I'm also using I2C1 to transmit other data.

After some debugging, I went through the STM32F103RGproduct manual , page 272, figure 50 - DMA1 Request Mapping picture states that the USART2 and I2C1 share the DMA1 channels. I kept doing some testing, concluding that this happens whenusing: - USART2 with DMA RX enabled, and - I2C1 in master mode using the IRQ Handlers as in ''

OptimizedI2Cexamples'', EVENwith DMA disabled.

I can avoid this problem making 2 tricks: 1) Or disabling the USART2 DMA. 2) Or

writinginto the I2C1 usingthe ''I2C_CheckEventfunction''way,

instead of using the I2C1 IRQ Handlers way as in''

OptimizedI2Cexamples''.

Well, I don't know exactly why this problem occurs. Is there any kind of incompatibility between the USART2 with DMA mode and the I2C1 with IRQ Handlers? This is my USART2 configuration:

RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
USART_DeInit(USART2);
USART_StructInit(&USART_InitStruct);
USART_InitStruct.USART_BaudRate = 57600;
USART_InitStruct.USART_WordLength = USART_WordLength_8b;
USART_InitStruct.USART_StopBits = USART_StopBits_1;
USART_InitStruct.USART_Parity = USART_Parity_No;
USART_InitStruct.USART_Mode = (USART_Mode_Rx | USART_Mode_Tx);
USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_Init(USART2, &USART_InitStruct);
USART_ClearFlag(USART2, USART_FLAG_RXNE | USART_FLAG_TC);
USART_DMACmd(USART2, USART_DMAReq_Rx, ENABLE);

This is the DMA configuration:

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
DMA_DeInit(DMA1_Channel6);
DMA_StructInit(&DMA_InitStructure);
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_PeripheralBaseAddr = USART2->DR;
DMA_InitStructure.DMA_MemoryBaseAddr = rx_buf;
DMA_InitStructure.DMA_BufferSize = rx_buf_sz;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_Init(DMA1_Channel6, &DMA_InitStructure);

And the I2C configuration:

RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1, ENABLE);
I2C_DeInit(I2C1 );
I2C_ClearFlag(I2C1, I2C_FLAG_SMBALERT | I2C_FLAG_TIMEOUT | I2C_FLAG_PECERR | I2C_FLAG_OVR | I2C_FLAG_AF | I2C_FLAG_ARLO | I2C_FLAG_BERR);
I2C_ClearITPendingBit(I2C1, I2C_IT_SMBALERT | I2C_FLAG_TIMEOUT | I2C_IT_PECERR | I2C_IT_OVR | I2C_IT_AF | I2C_IT_ARLO | I2C_IT_BERR);
I2C_ITConfig(I2C1,I2C_IT_EVT,ENABLE);
I2C_ITConfig(I2C1,I2C_IT_ERR,ENABLE);
I2C_ITConfig(I2C1,I2C_IT_BUF,ENABLE);

I really hope to hear from you :p #uart-dma-i2c-stm32f1

[Tesla DeLorean]

Posted on March 14, 2014 at 14:47

DMA_InitStructure.DMA_PeripheralBaseAddr = USART2->DR;

Should be &USART2->DR me thinks.

[Martin.Sergio]

Posted on March 14, 2014 at 15:14 Sorry, this is a misspeling writting the post.

If that were the

problem

would not work

either

case 2

:

2) Or 

writing into the I2C1 using the ''I2C_CheckEvent function'' way, 

instead of using the I2C1 IRQ Handlers way as in ''

OptimizedI2Cexamples''.

''

[Tesla DeLorean]

Posted on March 14, 2014 at 15:41

If that were the

problem

would not work

either

case 2

:

Ok, but I'm working with a selective cut-n-paste, a failed one at that, on a chip and protocol I'm not using. Perhaps the problem lies elsewhere? Try to create a complete/consise example of your problem, that is compilable. Have you reviewed the errata, or considered pin conflicts?

[Martin.Sergio]

Posted on March 14, 2014 at 17:26

The misspelling in the post wasn´t in the code. And, about the pinout, in all cases I initialize the same pinout, so i think that the pinout is not the problem.

It is going to take me some time to complete an example that is compilable, because my application runs with FreeRTOS, and the UART2 that I'm using, receives data from a XBee module and the I2C that I'm using, is sending data to a LCD. The most strange thing about the problem is that: 1.- If I have the I2C handlers enabled and the UART is working without DMA, everything works fine. 2.- If I use the I2C with the IRQs disabled and the UART is working with DMA, everything works fine. 3.- But if I have the I2C handlers enabled and the UART is working with DMA, then the problem happens. Between 1 and 3 the only difference in the code is the DMA for UART is enabled, and between 2 and 3 the only difference in the code is how the application is writing in the I2C. Thanks in advance and thank you for your time.