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1

utFAT / DMA with SPI for SD Cards

« on: July 11, 2012, 03:26:27 AM »

Hi Mark,

Have you attempted or given some thought into using DMA for SPI? I'm *trying* to implement DMA in the SD write routine for my M52259 board, but I'm having no luck.

Specifically, I'm trying to replace the WRITE_SPI_CMD(BYTE) function. Here is what I have so far:

Code: [Select]

void utWriteSPICmdWithDMA(unsigned char *ptrBuf, signed long ulLength)
{
        // Allow access to SPI for DMA
GPACR0 = SUP_USER_FULL_ACCESS;
PACR_QSPI = SUP_USER_FULL_ACCESS;

// DMA
    // Config SPI registers
    QAR = QSPI_TRANSMIT_RAM_0;
    QWR = ((0 << QSPI_START_SHIFT) | (0 << QSPI_END_SHIFT));
   
    // Setup DMA
    DMA_SR_BCR2 = ulLength;
    DMA_SAR2  = (unsigned long)ptrBuf;                          // address of first byte to be transferred  (SARn)
   
    DMA_DAR2  = (unsigned long)(QSPI_ADD + 0x14);                                // address of first destination byte       (DARn) = QDR
    DMA_DCR2  = (DCR_BWC_16K | DCR_SINC | /*DCR_DINC |*/ DCR_SSIZE_BYTE | DCR_DSIZE_BYTE | DCR_START); // set up DMA operation (DCRn) and start DMA transfer
   
    while (!(DMA_SR_BCR2 & DSR_DONE)) { };                 // wait until the transfer has terminated

QDLYR = QSPI_SPE;

// DMA transfer done.
    DMA_SR_BCR2 = DSR_DONE;                                          // clear all status bits ready for future transfer
}
After running this code I probed the clock, DataIn, and ChipSelect lines, all look OK. But no writes ever take place...the QSPI data register is always empty and the DMA status register reports no error either.

There are almost NO examples or anything online relating to using DMA with QSPI on my board (or any other boards for that matter!). Your DMA+UART code helps, but there are differences (I'm guessing) that prevent it from working. Shouldn't DMA automatically take care of handling the SPI though?

Does anyone have any ideas as well? Insights? Anything is appreciated!

Thanks!
Justin

2

utFAT / SD Card Performance

« on: June 28, 2012, 01:51:43 AM »

Hi Mark,

I'm currently using a 16GB SD card hooked up via SPI to my M52259DEMO board to log incoming CAN data (and also send the data to a server program on the PC). The CAN is set to 1 Mb/s, and each message has an 8byte payload. I use a temporary 1KB buffer in RAM to store the data (since I know that SD cards like larger data sets).
The data can come in at either 100, 1000, or 2000 messages/second.

The system can keep up with saving 100 and 1000 messages/sec, but at 2000 it can't. I only get about 1500/second, even after I tried to streamline my application. If I disable SD logging, my system can keep up with 2000 (as I can see from my server program).

I've traced through the SD write routines (through utFAT, mass_storage.c, etc), and I don't see any use of DMA. Is there a way I can easily enable it? Or do I have to manually implement it?

Also, does uTasker support other high-speed "tricks", such as 4-bit mode or setting the card to use "burst mode"?

In short, is there anything I can do to improve performance?

Thank you!
Justin