STM32F4 external Sdram data to serial peripheral with dma

[Antonio Alberto Iznaga Marín]

Posted on June 07, 2018 at 01:45

I have a large data buffer stored in external sdram. I'd like to send data to a serial peripheral (uart, spi or iis) directly on a dma transfer. Is it possible to do so?. Every FMC sdram example available move data from sdram to internal ram.

Thanks in advance.

Tony 

[Tesla DeLorean]

Posted on June 07, 2018 at 02:35

In this context you could use USART+DMA to send up to 64KB at a time, the real issue would be overwhelming the host. You'd probably want some protocol to control flow and check integrity as you offload the data.

I'd expect there would be examples of DMA transfers from SDRAM to a memory mapped LCD/FMC, standard settings/configuration for USART+DMA should support a buffer in Internal SRAM or External SDRAM.

Something like X-MODEM would work at 921600 baud

[Antonio Alberto Iznaga Marín]

Posted on June 19, 2018 at 00:15

Thanks Clive, following on your advice i was able to set a dma transfer from external SDRAM memory space to IIS peripheral for sending audio samples to an audio codec as intended. Only noted that when configuring FMC controller through CubeMx a piece of code is missing (according to available examples)  concerning a FMC_SDRAM_CommandTypeDef setting. Since i was using the exact same chip as Discovery boards on my design i was able to copy the code from the examples and it worked.

Best Regards

Tony

PS:

Here its the code missing from CubeMx initialization (I'm using CubeMx v4.20)

file fmc.c

FMC_SDRAM_CommandTypeDef command;

SDRAM_HandleTypeDef hsdram2;

FMC_SDRAM_CommandTypeDef* Command = &command;

Command->CommandMode = FMC_SDRAM_CMD_CLK_ENABLE;

Command->CommandTarget = FMC_SDRAM_CMD_TARGET_BANK2;

Command->AutoRefreshNumber = 1;

Command->ModeRegisterDefinition = 0;

HAL_SDRAM_SendCommand(&hsdram2, Command, 0x1000);

HAL_Delay(100);

Command->CommandMode = FMC_SDRAM_CMD_PALL;

Command->CommandTarget = FMC_SDRAM_CMD_TARGET_BANK2;

Command->AutoRefreshNumber = 1;

Command->ModeRegisterDefinition = 0;

HAL_SDRAM_SendCommand(&hsdram2, Command, 0x1000);

Command->CommandMode = FMC_SDRAM_CMD_AUTOREFRESH_MODE;

Command->CommandTarget = FMC_SDRAM_CMD_TARGET_BANK2;

Command->AutoRefreshNumber = 4;

Command->ModeRegisterDefinition = 0;

HAL_SDRAM_SendCommand(&hsdram2, Command, 0x1000);

tmpmrd = (uint32_t)SDRAM_MODEREG_BURST_LENGTH_2 |

SDRAM_MODEREG_BURST_TYPE_SEQUENTIAL |

SDRAM_MODEREG_CAS_LATENCY_3 |

SDRAM_MODEREG_OPERATING_MODE_STANDARD |

SDRAM_MODEREG_WRITEBURST_MODE_SINGLE;

Command->CommandMode = FMC_SDRAM_CMD_LOAD_MODE;

Command->CommandTarget = FMC_SDRAM_CMD_TARGET_BANK2;

Command->AutoRefreshNumber = 1;

Command->ModeRegisterDefinition = tmpmrd;

HAL_SDRAM_SendCommand(&hsdram2, Command, 0x1000);

HAL_SDRAM_ProgramRefreshRate(&hsdram2, REFRESH_COUNT);

[Vitaliy Chernobay]

Posted on June 19, 2018 at 07:03

This code is for graphics sdram for CubeMX 4.26