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Writing Data to PSRAM from DSP on RT685

I am using the RT685 platform, connecting a PSRAM through FlexSPI. The PSRAM (ISSI IS66WVR8M8FALL) is connected to PortA2, and there is a QSPI Flash connected to PortA1.

PSRAM was configured to access by AHB, FlexSPI was configured on MCU side after startup, then after a few minutes, wrote data from DSP side. When writing data from DSP side, there were some 0x00 data in the PSRAM, and the data looks regular. To debug this issue, I wrote 192 bytes 0x32 at once and then 0x33 ...

There is no problem of writing and reading data from MCU side. This issue only occurred when writing data from DSP side.

The configuration of FlexSPI,

const flexspi_config_t FLEXSPI_config = {
  .rxSampleClock = kFLEXSPI_ReadSampleClkLoopbackInternally,
  .enableSckFreeRunning = false,
  .enableDoze = true,
  .enableHalfSpeedAccess = false,
  .enableSckBDiffOpt = false,
  .enableSameConfigForAll = false,
  .seqTimeoutCycle = 65535,
  .ipGrantTimeoutCycle = 255,
  .txWatermark = 8U,
  .rxWatermark = 8U,
  .ahbConfig = {
    .ahbGrantTimeoutCycle = 255,
    .ahbBusTimeoutCycle = 65535,
    .resumeWaitCycle = 32,
    .buffer = { 
      { .priority = 0, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 1, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 2, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 3, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 4, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 5, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 6, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 7, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true }
    },
    .enableClearAHBBufferOpt = true,
    .enableReadAddressOpt = false,
    .enableAHBPrefetch = false,
    .enableAHBBufferable = true,
    .enableAHBCachable = false
  }
};

Configuration of PSRAM,

flexspi_device_config_t FLEXSPI_config_Device_SPIRAM = {
   .flexspiRootClk       = SPIRAM_ROOT_CLOCK_HZ,
   .isSck2Enabled        = false,
   .flashSize            = SPIRAM_SIZE_KBYTES,
   .CSIntervalUnit       = kFLEXSPI_CsIntervalUnit1SckCycle,
   .CSInterval           = 2,
   .CSHoldTime           = 3,
   .CSSetupTime          = 3,
   .dataValidTime        = 0,
   .columnspace          = 0U,
   .enableWordAddress    = false,
   .AWRSeqIndex          = SPIRAM_LUT_SEQ_IDX_WRITE,
   .AWRSeqNumber         = 1U,
   .ARDSeqIndex          = SPIRAM_LUT_SEQ_IDX_READ,
   .ARDSeqNumber         = 1U,
   .AHBWriteWaitUnit     = kFLEXSPI_AhbWriteWaitUnit2AhbCycle,
   .AHBWriteWaitInterval = 1,
   .enableWriteMask      = false,
};

Does anyone have idea about this problem?

i.MXRT 600

Re: Writing Data to PSRAM from DSP on RT685

Hi @VincentW

I think the issue is most likely caused by incorrect FlexSPI AHB configuration for multi-master access.

Currently, all AHB buffers are assigned to master 0.

 .buffer = { 
      { .priority = 0, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 1, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 2, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 3, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 4, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 5, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 6, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true },
      { .priority = 7, .masterIndex = 0U, .bufferSize = 256U, .enablePrefetch = true }
    },

You can try to assign one buffer to the dsp.

Enabling AHB write buffering (enableAHBBufferable = true) may delay or merge writes, which is not suitable for PSRAM and can lead to missing data.

You can try to

enableAHBBufferable = false;

BR

Harry