I am attempting to use the DMA to auto-load PWM values for a motor control application. An example very similar to what I want to do is given in the RM0090, section 17.4.20 (for STM32F427). However, I'm missing some detail and can't get the DMA to transfer the values. We are running the controller at 20kHz and I want to update at 80kHz (the motor PWM freq.), so I am trying to do four bursts of three PWM values that are precalculated during the 20kHz loop. My code is below. You can ignore all the FOC motor control stuff; that is known good code from another implementation. Thanks in advance for your help.
#define MOTOR_PWM_STREAM DMA2_Stream1
#define MOTOR_PWM_DMA_IRQn TIM1_UP_TIM10_IRQn
#define MOTOR_PWM_CHANNEL DMA_Channel_6
#define MOTOR_PWM_BURST_SIZE 3
#define MOTOR_PWM_NUM_BURSTS 4
#define MOTOR_PWM_DMA_BUFF_SIZE (MOTOR_PWM_BURST_SIZE*MOTOR_PWM_NUM_BURSTS)
//DMA to load precalulated PWM values
static const DMA_InitTypeDef svm_DMA_InitStruct = {
.DMA_Channel = MOTOR_PWM_CHANNEL,
.DMA_PeripheralBaseAddr = (uint32_t) &TIM1->DMAR,
.DMA_Memory0BaseAddr = (uint32_t) &svm_dma_buf[0],
.DMA_DIR = DMA_DIR_MemoryToPeripheral,
.DMA_BufferSize = MOTOR_PWM_DMA_BUFF_SIZE,
.DMA_PeripheralInc = DMA_PeripheralInc_Enable,
.DMA_MemoryInc = DMA_MemoryInc_Enable,
.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord, // 16bit data
.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord,
.DMA_Mode = DMA_Mode_Normal,
.DMA_Priority = MOTOR_PWM_DMA_CHANNEL_PRI,
.DMA_FIFOMode = DMA_FIFOMode_Disable,
.DMA_FIFOThreshold = DMA_FIFOThreshold_1QuarterFull,
.DMA_MemoryBurst = DMA_MemoryBurst_Single,
.DMA_PeripheralBurst = DMA_PeripheralBurst_Single
};
// Initialize the DMA to transfer PWM values into CCRx registers upon TIM1 Update request
static void motor_init_svm_dma(void) {
MOTOR_PWM_DMA_CLK_ENABLE();
// DMA Configuration for transferring SVM vectors into PWM registers:
DMA_Cmd(MOTOR_PWM_STREAM, DISABLE);
DMA_DeInit(MOTOR_PWM_STREAM);
DMA_Init(MOTOR_PWM_STREAM, (DMA_InitTypeDef*) &svm_DMA_InitStruct);
// NOTE - I have commented this out because I don't think the interrupt is needed to cause a DMA request - is that correct? Even if I uncomment this, it doesn't work.
// // Enable the DMA interrupt and set to the highest priority
// NVIC_Init((NVIC_InitTypeDef*) &svm_NVIC_InitStructure);
TIM_DMAConfig(MOTOR_PWM_TIMER, TIM_DMABase_CCR1, TIM_DMABurstLength_3Transfers);
TIM_SelectCCDMA(MOTOR_PWM_TIMER, ENABLE);
}
// Load the next four pwm values based on current position
static void motor_load_pwm_dma(void) {
// Turn off the update so it doesn't trigger during this routine
// Also turn off the DMA for now
TIM_DMACmd(MOTOR_PWM_TIMER, TIM_DMA_Update, DISABLE);
DMA_Cmd(MOTOR_PWM_STREAM, DISABLE);
// A term to predict the motor physical movement for the next 4 cycles
int32_t phase_adv = (int32_t)(mot_ctrl_obj.rpm*0.02667F);
uint32_t i;
for(i=0; i<4; i++) {
// Calculate Sin & Cos from desired motor angle
motor_SineCosine_f(&motor_ctrl, phase_adv*i);
// Calculate Ialpha, Ibeta, and Id, Iq from Sin, Cos, Ia, Ib
motor_ControlClarkePark_f(&motor_ctrl);
// Calculate control values based on motor mode: Vq, Vd & desired angle
motor_mode_specific_ctrl();
// Calculate qValpha, qVbeta from Sin, Cos, Vd, Vq
motor_ControlInversePark_f(&motor_ctrl);
// Calculate PWM duty cycles from qValpha & qVbeta
motor_SpaceVectorModCalcs(motor_ctrl.qValpha, motor_ctrl.qVbeta, mot_ctrl_obj.pwm_registers, motor_ctrl.svm_ref_vectors);
// PWM Output - Mapped based on motor mode
svm_dma_buf[i*3] = mot_ctrl_obj.pwm_registers[0];
svm_dma_buf[i*3+1] = mot_ctrl_obj.pwm_registers[1];
svm_dma_buf[i*3+2] = mot_ctrl_obj.pwm_registers[2];
}
// Re-enable timer request and DMA
TIM_DMACmd(MOTOR_PWM_TIMER, TIM_DMA_Update, ENABLE);
DMA_Cmd(MOTOR_PWM_STREAM, ENABLE);
}
