Digital Value to DAC

[manoritesameer]

Posted on June 24, 2014 at 21:06

Hello,

       I am using the STM32F4 discovery board. I have a project in which I have a timer which generate an interrupts @ 100Khz. In the ISR it stores a new value to a variable.        Now how can I use the DMA to send this value to the DAC which is updated at the same rate.ThanksRegardsSameer #stm32

[warcatz]

Posted on June 24, 2014 at 22:16

hi ,

i do it like this :

#define BITDEPTH 12 // 12 bits DAC
#define SAMPLERATE (SYSCLK / (1 << 
BITDEPTH
)) // Best audio quality 192MHz / (1 << 11) = 46875Hz
// Initialise Timer2
void Timer2_Init(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
// Clock enable
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
// Timer2 init
TIM_TimeBaseStructure.TIM_Period
= 
SYSCLK
/ SAMPLERATE;
TIM_TimeBaseStructure.TIM_Prescaler
= 
0
; // 192Mhz tick (adjust per your clock)
TIM_TimeBaseStructure.TIM_ClockDivision
= 
TIM_CKD_DIV1
;
TIM_TimeBaseStructure.TIM_CounterMode
= 
TIM_CounterMode_Up
;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
// Timer2 enable
TIM_ARRPreloadConfig(TIM2, ENABLE);
TIM_Cmd(TIM2, ENABLE);
}
// *********************************************************************************
// Timer2 interrup and DAC2 init
void Mod_Int_Init(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
GPIO_InitTypeDef DAC_GPIO_Init; 
RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);
//---------------------------------------------
// init from Timer2 Interrupt
TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE);
NVIC_InitStructure.NVIC_IRQChannel
= 
TIM2_IRQn
;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority
= 
0
;
NVIC_InitStructure.NVIC_IRQChannelSubPriority
= 
0
;
NVIC_InitStructure.NVIC_IRQChannelCmd
= 
ENABLE
;
NVIC_Init(&NVIC_InitStructure);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); 
DAC_GPIO_Init.GPIO_Pin
= 
GPIO_Pin_5
;
DAC_GPIO_Init.GPIO_Mode
= 
GPIO_Mode_AN
;
DAC_GPIO_Init.GPIO_Speed
= 
GPIO_Speed_25MHz
;
DAC_GPIO_Init.GPIO_OType
= 
GPIO_OType_PP
;
DAC_GPIO_Init.GPIO_PuPd
= 
GPIO_PuPd_NOPULL
;
GPIO_Init(GPIOA, &DAC_GPIO_Init);
DAC_Cmd(DAC_Channel_2,ENABLE);
}
// *********************************************************************************
// Timer2 interrupt
void TIM2_IRQHandler(void)
{
if(File_Loaded != 0)
if(SoundBuffer.writePos != SoundBuffer.readPos) 
{
// Output the Audio as mono (only DAC2 pin is free)
Sound_Out = (uint16_t)(((SoundBuffer.left[SoundBuffer.readPos] + SoundBuffer.right[SoundBuffer.readPos])) >> 1);
DAC_SetChannel2Data(DAC_Align_12b_R,Sound_Out);
SoundBuffer.readPos++;
SoundBuffer.readPos &= SOUNDBUFFERSIZE - 1;
}
Int_Count++;
// Clear interrupt flag
TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
}

I hope it can help you . It's a part from my st429 mod player. Tou can get the full source on this page :

https://sites.google.com/site/suprabotics/stm429-discovery-expansion-board-v2-0/amiga-module-player-with-the-stm32f429

Cheers.

[warcatz]

Posted on June 24, 2014 at 22:17

double post .. delete thisd one ...

[Tesla DeLorean]

Posted on June 24, 2014 at 23:02

If you're computing it in a periodic interrupt, could you not just write it to the DAC then? Otherwise you've got to pay particular attention to keeping the IRQ and DMA synchronized.

[manoritesameer]

Posted on June 25, 2014 at 20:04

thank you all... U all guys are great. Also I would like to thank Clive separately for ur great help and amazing spirit.