Posted on July 20, 2014 at 22:55
Hi guys!
Is there anyone that has some experience in setting up this kind of DMA streaming?
I would like to stream 16-bit data to an external DAC, with no sweat for the processor. I've read that timer triggered DMA transfers to SPI are a viable option, and also found some sample code for it.
I have configured my TIM1 to run in OC mode, SPI1 relevant pins and the DMA peripheral toDMA2_Stream3 using Channel_6 as is written in the datasheet.
When I run my code the output is dead, if I look at the DR register for SPI1 is also 0x0000, so no data is pouring in from the DMA.
Does anyone have any suggestions? Should I include some additional code to the main loop, that I am not aware of (I initialize all the peripherals, and in my understanding this should work)?
Here is my initialization function, that I use at startup:
void spi1_init(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
DMA_InitTypeDef DMA_InitStructure;
SPI_InitTypeDef SPI_InitStruct;
GPIO_InitTypeDef GPIO_InitStructure;
/*
* GPIO configuration
*/
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
/* Configure pins used by SPI1:
* PA4 = NSS
* PA5 = SCLK
* PA6 = MISO
* PA7 = MOSI */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_6 | GPIO_Pin_5 | GPIO_Pin_4;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* Connect SPI1 pins to SPI alternate function */
GPIO_PinAFConfig(GPIOA, GPIO_PinSource4, GPIO_AF_SPI1);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_SPI1);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_SPI1);
/* Enable the SPI peripheral clock */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);
/* Configure SPI1 in Mode 0:
* CPOL = 0 --> clock is low when idle
* CPHA = 0 --> data is sampled at the first edge
*
* SPI Master mode, 8 bits of data, clock prescalar is 256, MSB is
* transmitted first. */
SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
SPI_InitStruct.SPI_Mode = SPI_Mode_Master;
SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b;
SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;
SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;
SPI_InitStruct.SPI_NSS = SPI_NSS_Soft | SPI_NSSInternalSoft_Set;
SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_256;
SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_Init(SPI1, &SPI_InitStruct);
/* Enable SPI */
SPI_Cmd(SPI1, ENABLE);
/*
* TIM1 Configuration
*/
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 150;
TIM_TimeBaseStructure.TIM_Prescaler = (uint16_t)(SystemCoreClock / 40000000) - 1;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
/* PWM1 Mode configuration: Channel1 */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 5;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init(TIM1, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable);
TIM_SelectOutputTrigger(TIM1, TIM_TRGOSource_Update);
TIM_ARRPreloadConfig(TIM1, ENABLE);
TIM_Cmd(TIM1, ENABLE);
/*
* DMA2 Configuration
*/
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);
DMA_DeInit(DMA2_Stream3);
DMA_StructInit(&DMA_InitStructure);
DMA_InitStructure.DMA_Channel = DMA_Channel_6;
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&SPI1->DR;
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&test_buffer;
DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
DMA_InitStructure.DMA_BufferSize = TEST_BUFFER_LEN;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
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_ITConfig(DMA2_Stream3, DMA_IT_TC, DISABLE);
DMA_Init(DMA2_Stream3, &DMA_InitStructure);
DMA_Cmd(DMA2_Stream3, ENABLE);
TIM_DMACmd(TIM1, TIM_DMA_Update, ENABLE);
}
Thanks for your suggestions.
BR,
Blaz
Any other suggestions? Could it be that the discovery board pin mappings are the problem (SPI PA pins are already used on discovery for LIS302DL)? Should I be clearing some flags, that I am not aware of?
Thanks again!
