# [STM32F103RB][C] - DMA, can't change PWM period

Hello i woul'd like change PWM period with DMA. I wrote code but i don't know why LED BLINKING with constant time

#include "stm32f10x.h"
#include "stm32f1xx_nucleo.h"
#include "stm32f10x.h"

int i =0;
u16 PWM_Buf[198];

void TIMInit(void);
void GPIOInit(void);
void DMAInit(void);
void PWMInit(void);

int main(void)
{
GPIOInit();
TIMInit();
DMAInit();
PWMInit();

for(i = 0;i<198;i++)
{
PWM_Buf[i] = i * 10; // <-------- VALUE OF TIM PERIOD
}

while(1)
{
}
}
void TIMInit(void)
{
TIM_TimeBaseInitTypeDef TIMInit;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);

TIMInit.TIM_Period = 1000;
TIMInit.TIM_Prescaler = 64000;

TIMInit.TIM_ClockDivision = TIM_CKD_DIV1;
TIMInit.TIM_CounterMode = TIM_CounterMode_Up;

TIMInit.TIM_RepetitionCounter = 200;

TIM_TimeBaseInit(TIM1, &TIMInit);
}

void GPIOInit(void)
{
GPIO_InitTypeDef GPIOInit;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

GPIOInit.GPIO_Pin = GPIO_Pin_8;
GPIOInit.GPIO_Mode = GPIO_Mode_AF_PP;
GPIOInit.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIOInit);
}

void DMAInit(void)
{

DMA_InitTypeDef DMAInit;

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
DMA_DeInit(DMA1_Channel5);
DMAInit.DMA_DIR = DMA_DIR_PeripheralDST;
DMAInit.DMA_BufferSize = 198;
DMAInit.DMA_PeripheralInc = DMA_PeripheralInc_Enable;
DMAInit.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMAInit.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
DMAInit.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
DMAInit.DMA_Mode = DMA_Mode_Circular;
DMAInit.DMA_Priority = DMA_Priority_High;
DMAInit.DMA_M2M = DMA_M2M_Disable;

DMA_Init(DMA1_Channel5, &DMAInit);

DMA_Cmd(DMA1_Channel5, ENABLE);
}

void PWMInit(void)
{
TIM_OCInitTypeDef  PWMInit;

PWMInit.TIM_OCMode = TIM_OCMode_PWM1;
PWMInit.TIM_OutputState = TIM_OutputState_Enable;
PWMInit.TIM_Pulse = 500;
PWMInit.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init(TIM1, &PWMInit);
TIM_DMACmd(TIM1, TIM_DMA_Update, ENABLE);
TIM_Cmd(TIM1, ENABLE);
TIM_CtrlPWMOutputs(TIM1, ENABLE);
}

• Thank you for providing the full source code along with the question. – Morten Jensen Jan 29 '18 at 14:37
• It's not full code i cutted usart communication, and motor driver. I only paste DMA TIMER AND PWM configuration. I thought i wrote good code but i dont know why period doesnt be diffrent. I need only help for it. – Member Cicada Jan 29 '18 at 14:42
• Are you sure this is correct? DMAInit.DMA_PeripheralInc = DMA_PeripheralInc_Enable; Does this really want to be set to inc? I suspect this is at least one issue you have and it wants to be DMA_PeripheralInc_Disable. I think. – DiBosco Jan 29 '18 at 14:54
• It's not probably problem i disabled this and the same. I don't see anything wrong. I thought someone maybe caught problem – Member Cicada Jan 29 '18 at 15:02
• You need to put @DiBosco for me to see your response. When I did this to create PWMs many years back, my DMA's CPAR register was set to the CCR, not the ARR register which I think you have used here. – DiBosco Jan 29 '18 at 15:46

DMAInit.DMA_PeripheralBaseAddr = (u16)TIM1_ARR_Address;


You can't cast a pointer as an unsigned 16 bit. Pointers are 32 bit on this platform.
Like this: (uint32_t)&TIM1->ARR.

DMAInit.DMA_PeripheralInc = DMA_PeripheralInc_Enable;


You can't increment the peripheral address, the next cycle would be TIMx_RCR, then TIMx_CCR1 etc.

• I'd already pointed out the peripheral inc thing to him and he'd said that'd made no difference. The pointer thing is good point though. – DiBosco Jan 29 '18 at 15:47
• I know it's stupid, but can I ask for the code to be corrected because I have no idea how to do it. I would be very grateful – Member Cicada Jan 29 '18 at 17:00
• I wonder how you wrote this code if you have no idea what to change or at least articulate yourself to ask what to change!!? – charansai Jan 29 '18 at 20:09
• @MemberCicada why have you configured PeripheralDataSize as word and MemoryDataSize as half word? – charansai Jan 29 '18 at 20:24
• @charansai the timer is 16 bit and half word access is possible. – Jeroen3 Jan 30 '18 at 7:05