Parallel data transmission using GPIO and DMA STM32F051xx

[SwagWalker77]

Posted on August 13, 2016 at 19:25

Hi all! I'm trying to create a parallel synchronous data transmission using DMA and GPIO on a STM32F051 MCU. I've been following the AN4666 document that ST released, but is set up for STM32F4 MCUs. I also don't use HAL drivers, unlike the example code ST has for that document.

I'm having issues with getting the DMA to output data to the pins. I see only 0 on the pins. I should see all 1s as I set the data buffer to 0xFFFF for all location in the buffer. I'm guessing I don't have DMA set up properly or have it tied correctly up to TIM1. TIM1 is currently outputting a 20KHz PWM signal as expected.

#include ''base_lib.h''


/* Private typedef -----------------------------------------------------------*/

GPIO_InitTypeDef GPIO_InitStructure;

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

TIM_OCInitTypeDef TIM_OCInitStructure;

NVIC_InitTypeDef NVIC_InitStructure;

DMA_InitTypeDef DMA_InitStructure;


static uint16_t asrc_buffer[FULL_FRAME_SIZE];


uint32_t counter=0;



/* Private function prototypes -----------------------------------------------*/

static void Data_GPIO_Config(void);

static void Timer_GPIO_Config(void);

static void ConfigureTIMxAsPWM_withDMA(void);

//static void SetupTimer(void);

/* Private functions ---------------------------------------------------------*/


/**

* @brief Main program

* @param None

* @retval None

*/

int main(void)

{


//Create data to be sent

for (counter = 0; counter < 
FULL_FRAME_SIZE
- 1 ; counter++)

{

asrc_buffer[counter] &= 0xFFFF;

}



/* Configure the Data GPIO in output mode */

Data_GPIO_Config();


//Set up timer GPIO

Timer_GPIO_Config();


/* Start TIM PWM with DMA1 channel 5 */

ConfigureTIMxAsPWM_withDMA();


while (1){}


}


/**

* @brief Configure the Data GPIO in output mode

*

* @note None

* @param None

* @retval None

*/

void Data_GPIO_Config(void)

{


RCC->AHBENR |=RCC_AHBENR_GPIOCEN; // Enable GPIO port C


GPIO_InitStructure.GPIO_Pin = GPIO_Pin_All;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOC, &GPIO_InitStructure);

}


/**

* @brief Configure the Timer GPIO

*

* @note None

* @param None

* @retval None

*/

void Timer_GPIO_Config(void)

{


RCC->AHBENR |=RCC_AHBENR_GPIOAEN; // Enable GPIO port A


GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;


//place before GPIO_Init to avoid pin being connected

GPIO_PinAFConfig(GPIOA,GPIO_PinSource9,GPIO_AF_2);


GPIO_Init(GPIOA, &GPIO_InitStructure);

}


void ConfigureTIMxAsPWM_withDMA(void)

{


/* TIM1 clock enable */

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1 , ENABLE);

/* DMA1 clock enable */

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);


uint16_t Period;


Period = 1000000 / 20000; // 20 KHz for 1MHz prescaled



/* Time Base configuration */

TIM_TimeBaseStructure.TIM_Prescaler = 48-1;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseStructure.TIM_Period = Period - 1;

TIM_TimeBaseStructure.TIM_ClockDivision = 0;

TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;


TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);


// Channel 2

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

TIM_OCInitStructure.TIM_Pulse = Period/2 ; //50%

TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_Low;


TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;

TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Reset;


TIM_OC2Init(TIM1, &TIM_OCInitStructure);



//reset DMA1 channel5 to default values

DMA_DeInit(DMA1_Channel5);


DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&asrc_buffer; //Data source, aka our data buffer

DMA_InitStructure.DMA_DIR=DMA_DIR_PeripheralDST; // Memory to peripheral

DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //Always write to same register

DMA_InitStructure.DMA_PeripheralBaseAddr=(uint32_t)&(GPIOC->ODR); //Where we want to output the data

DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //Increment through data buffer

DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord; // 16-bit register

DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord; // 16-bit array

DMA_InitStructure.DMA_Mode = DMA_Mode_Normal; //not circular

DMA_InitStructure.DMA_Priority = DMA_Priority_High;


DMA_Init(DMA1_Channel5, &DMA_InitStructure);


// Enable DMA1 Channel5 Transfer Complete interrupt

DMA_ITConfig(DMA1_Channel5,DMA_IT_TC,ENABLE);



//Enable DMA1 channel IRQ Channel5 */

NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel4_5_IRQn; //DMA1_Channel4 and Channel5 interrupts

NVIC_InitStructure.NVIC_IRQChannelPriority=0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);


//Enable the TIM1 compare capture 1 dma requests

TIM_DMACmd(TIM1,TIM_DMA_CC1,ENABLE);


/* TIM1 Main Output Enable */

TIM_CtrlPWMOutputs(TIM1, ENABLE);


// turning on TIM1 and PWM outputs

TIM_Cmd(TIM1, ENABLE);


}


void DMA1_Channel5_IRQHandler(void)

{

//stop the clock cycles. TODO: use bare metal register instead

TIM_Cmd(TIM1,DISABLE);


if(DMA_GetITStatus(DMA1_IT_TC5))

{


//Clear DMA1 Channel5 Half Transfer, Transfer Complete and Global interrupt pending bits

DMA_ClearITPendingBit(DMA1_IT_GL5);

}

}

[Tesla DeLorean]

Posted on August 13, 2016 at 21:14

Use = 0xFFFF, not &= 0xFFFF, the array is probably already zero.

Check if DMA1 supports M2M operation, not sufficiently familiar with the F051, check RM

[SwagWalker77]

Posted on August 13, 2016 at 23:47

Changed to =0xFFFF. From what the RM says, DMA1 should support M2M. My attempt is to go from memory-to-peripheral, which it also supports.

I did see in the RM on table 29 that for TIM1, I should be using Channel 3. It says for TIM1_CH2 the DMA request should be channel 3. I have changed that as well.

[SwagWalker77]

Posted on August 14, 2016 at 00:28

Still not working, but I did find some potential help from an older forum post with a similar problem.

https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Data%20transfer%20from%20GPIO%20port%20to%20RAM%20buffer%20using%20DMA%20upon%20receiving%20a%20trigger%20signal%20on%20the%20timer%20capture%2...