STM32F103 and I2C TX using DMA, byte array issue

[Bogdan]

Hello, i have the following setup code for i2c and DMA, where i use i2c1 to send some buffer data to a display.

 DMA_DeInit(DMA1_Channel6);
	 DMA_InitStructure.DMA_BufferSize = DMA_I2C_BUFFER_SIZE;//BufferSize;
	 DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
	 DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
	 DMA_InitStructure.DMA_PeripheralDataSize = DMA_MemoryDataSize_Byte;
	 DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
	 DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
	 // DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
	 DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
	 DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)I2C1_DR_Address;
	 DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)SSD1306_Buffer;//I2C1_Buffer_Tx;
	 DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
	 DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
	 DMA_Init(DMA1_Channel6, &DMA_InitStructure);
	
	 I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;
	 I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;
	 I2C_InitStructure.I2C_OwnAddress1 = 0;
	 I2C_InitStructure.I2C_Ack = I2C_Ack_Enable; // enable acknoledge
	 I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;
	 I2C_InitStructure.I2C_ClockSpeed = 400000; //400kHz (Fast Mode) (
	 I2C_Init(I2C1, &I2C_InitStructure);
	 DMA_Cmd(DMA1_Channel6, ENABLE);

And i have the buffer function to send the data via DMA

void I2C_Master_BufferWrite(uint8_t* pBuffer, uint32_t NumByteToWrite, uint8_t SlaveAddress )
 
{
	//__IO uint32_t Adress = 0;
 __IO uint32_t temp = 0;
 __IO uint32_t Timeout = 0;
 /* Configure the DMA channel for I2Cx transmission */
 DMA_InitTypeDef I2CDMA_InitStructure;
 I2CDMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)pBuffer;
 I2CDMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
 I2CDMA_InitStructure.DMA_BufferSize = (uint32_t)NumByteToWrite;
 I2CDMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)I2C1_DR_Address;
 
 DMA_Cmd(DMA1_Channel6, DISABLE);
 DMA_Init(DMA1_Channel6, &I2CDMA_InitStructure);
 DMA_Cmd(DMA1_Channel6, ENABLE);
 
 
 /* Enable the I2Cx DMA requests */
 I2C_DMACmd(I2C1, ENABLE);
 //I2C1->CR2 |= CR2_DMAEN_Set;
 /* Send START condition */
 I2C_GenerateSTART(I2C1, ENABLE);
 //I2C1->CR1 |= CR1_START_Set;
 /* Wait until SB flag is set: EV5 */
 while ((I2C1->SR1&0x0001) != 0x0001);
 
 /* Send slave address */
 I2C_Send7bitAddress(I2C1, SlaveAddress, I2C_Direction_Transmitter);
 
 /* Wait until ADDR is set: EV6 */
 while ((I2C1->SR1&0x0002) != 0x0002);
 
 
 /* Clear ADDR flag by reading SR2 register */
 temp = I2C1->SR2;
 
 /* Wait until DMA end of transfer */
 while (!DMA_GetFlagStatus(DMA1_FLAG_TC6));
 /* Disable the DMA1 Channel 6 */
 DMA_Cmd(DMA1_Channel6, DISABLE);
 /* Clear the DMA Transfer complete flag */
 DMA_ClearFlag(DMA1_FLAG_TC6);
 
 
 
 /* EV8_2: Wait until BTF is set before programming the STOP */
 while ((I2C1->SR1 & 0x00004) != 0x000004);
 /* Program the STOP */
 I2C_GenerateSTOP(I2C1,ENABLE);
 /* Make sure that the STOP bit is cleared by Hardware */
 while ((I2C1->CR1&0x200) == 0x200);
 
 
}

This piece of code is working somehow strange when i try to send more than 1 byte

I have the following example

 uint8_t mm[7]={0x11,0x22,0x33,0x44,0x55,0x66, 0x77 };
 
 I2C_Master_BufferWrite(mm, 5, 0x7A );

With a logic analyzer i get the followings.

 

So i would expect that it sends 5 bytes in order like 0x11 0x22 0x33 0x44 0x55, but it acts like it jumps some certain memory addresses.

What i am doing wrong here?

[Bogdan]

Hmmm,

i later found out that declaring my "mm" array as short mm[7] = { ......} makes the code works as expected.

But i wonder why?

It seems like normal uint8_t is using actually 2 bytes of memory?

This somehow confirms my guessing, that the dma points by 16 bits in the memory counter.

I'm not sure if this is compiler related, and not mcu

[Bob S]

Maybe not THE answer, but should be changed anyway so the HAL code doesn't use uninitialized structure contents. Change

 DMA_InitTypeDef I2CDMA_InitStructure;

to

 DMA_InitTypeDef I2CDMA_InitStructure = {0};

This ensures that ALL of the init structure is set to zeros. Your code leaves some fields set to whatever was in RAM (on the stack).

[Bogdan]

Hello, sorry for the delay.

the initial aproach was using standard periph library, i tried also to develop something under hall, but ran in stranger issues.

Unfortunately i abandoned the usage of dma with i2c, and moved everything to spi where i have higher data rates...