Posted on November 06, 2016 at 01:45Part: STM32F411
I've got a SPI transmit buffer that is 16 bytes long and I send SPI messages that are 16 bytes long.
The SPI bus runs at 50MHz, so I want to use DMA and the FIFO. In addition, I want to use the FIFO to read data from memory in Word mode and write data to the SPI peripheral in Byte mode - I believe this is called unpacking (Table 31 of RM0383, Figure 28 of RM0383).
So, I program the DMA as follows:
/* Peripheral DMA init*/
hdma_spi1_tx.Instance = DMA2_Stream3;
hdma_spi1_tx.Init.Channel = DMA_CHANNEL_3;
hdma_spi1_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
hdma_spi1_tx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_spi1_tx.Init.MemInc = DMA_MINC_ENABLE;
hdma_spi1_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_spi1_tx.Init.MemDataAlignment = DMA_MDATAALIGN_WORD;
hdma_spi1_tx.Init.Mode = DMA_NORMAL;
hdma_spi1_tx.Init.Priority = DMA_PRIORITY_MEDIUM;
hdma_spi1_tx.Init.FIFOMode = DMA_FIFOMODE_ENABLE;
hdma_spi1_tx.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_HALFFULL;
hdma_spi1_tx.Init.MemBurst = DMA_MBURST_SINGLE;
hdma_spi1_tx.Init.PeriphBurst = DMA_PBURST_SINGLE;
if (HAL_DMA_Init(&hdma_spi1_tx) != HAL_OK)
{
Error_Handler();
}
When this snippet of code is executed, Error_Handler() ends up getting called. When I dig into why, it seems that DMA_CheckFifoParam() is looking for the FIFOThreshold to be DMA_FIFO_THRESHOLD_FULL.
From reading the reference manual (RM0383), there is no such requirement. I think the code in DMA_CheckFifoParam() is mapping the requirement for burst transfers.
Thanks in advance.
#fifo #hal_dma_init #threshold
