sawtooth

[abdelkadermeftah62]

Posted on December 10, 2014 at 17:26

how i can generate a wave sawtooth ? please i need somone help me 

#poorly-framed-question

[Tesla DeLorean]

Posted on December 10, 2014 at 17:43

Can you use the DAC on your non-specific STM32 to output a pattern buffer in a loop?

A blind example from a prior thread

// STM32F4-Discovery Dual DAC 6.25 KHz Sine - [e-mail]
#include ''stm32f4_discovery.h''
/**************************************************************************/
const uint16_t Sine12bit[32] = {
2047, 2447, 2831, 3185,
3498, 3750, 3939, 4056,
4095, 4056, 3939, 3750,
3495, 3185, 2831, 2447,
2047, 1647, 1263, 909,
599, 344, 155, 38,
0, 38, 155, 344,
599, 909, 1263, 1647};
uint16_t SineTable[64];
/**************************************************************************/
void RCC_Config(void)
{
/* DMA1 clock and GPIOA clock enable (to be used with DAC) */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1 | RCC_AHB1Periph_GPIOA, ENABLE);
/* DAC and TIM6 Peripheral clock enable */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC | RCC_APB1Periph_TIM6, ENABLE);
}
/**************************************************************************/
void GPIO_Config(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
/* DAC channel 1 & 2 (DAC_OUT1 = PA.4)(DAC_OUT2 = PA.5) configuration */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_5;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOA, &GPIO_InitStructure);
}
/**************************************************************************/
void TIM6_Config(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
int Period;
Period = ((SystemCoreClock / 2) / 200000); // 200 KHz timebase, 6.25 KHz Sine
/* Time base configuration */
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Period = Period - 1;
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM6, &TIM_TimeBaseStructure);
/* TIM6 TRGO selection */
TIM_SelectOutputTrigger(TIM6, TIM_TRGOSource_Update);
/* TIM6 enable counter */
TIM_Cmd(TIM6, ENABLE);
}
/**************************************************************************/
#define DAC_DHR12RD_ADDRESS 0x40007428 // Right Align 12-bit Dual
void DAC_Config(void)
{
DAC_InitTypeDef DAC_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
/* DAC channel 1 and 2 Configuration */
DAC_InitStructure.DAC_Trigger = DAC_Trigger_T6_TRGO;
DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
DAC_Init(DAC_Channel_1, &DAC_InitStructure);
DAC_Init(DAC_Channel_2, &DAC_InitStructure);
/* DMA1_Stream5 channel7 configuration **************************************/
DMA_DeInit(DMA1_Stream5);
DMA_InitStructure.DMA_Channel = DMA_Channel_7;
DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR12RD_ADDRESS;
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&SineTable[0];
DMA_InitStructure.DMA_BufferSize = 32; // 16-bit x 64 / 2
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word; // 32-bit 16x2
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;
DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
DMA_Init(DMA1_Stream5, &DMA_InitStructure);
/* Enable DMA1_Stream5 */
DMA_Cmd(DMA1_Stream5, ENABLE);
/* Enable DAC Channel 1 and 2 */
DAC_Cmd(DAC_Channel_1, ENABLE);
DAC_Cmd(DAC_Channel_2, ENABLE);
/* Enable DMA for DAC Channel1 */
DAC_DMACmd(DAC_Channel_1, ENABLE);
}
/**************************************************************************/
int main(void)
{
int i, j;
j = 0;
for(i=0; i<32; i++)
{
SineTable[j++] = Sine12bit[i];
SineTable[j++] = Sine12bit[(i + 8) % 32]; // 90 degree phase shift on Channel 2
}
RCC_Config();
GPIO_Config();
TIM6_Config();
DAC_Config();
while(1); // Do not exit
}

[abdelkadermeftah62]

Posted on December 10, 2014 at 17:54

it's oblige to work with DMA ? 

[Tesla DeLorean]

Posted on December 10, 2014 at 17:59

it's oblige to work with DMA ?

No, but combining the DAC+TIM+DMA allows for controlled and accurate waveforms and periodicity.

The DAC also has other modes, you could review those also.