RTOS/DK-TM4C129X: DMA from Flash

David Dudley

Part Number: DK-TM4C129X

Tool/software: TI-RTOS

Is there a reason I can't transmit SPI using TIVAuDMA from ROM? Whenever I call SPI_transfer with a ROM pointer for the transmit message, I get a crash and an error.

over 8 years ago

0 ToddMullanix over 8 years ago

TI__Guru* 96960 points

I've moved your thread to the device forum.

Todd

0 Charles Tsai over 8 years ago

TI__Guru**** 190806 points

Hi David,

Please see below Bus Matrix Memory table. uDMA is not allowed to access ROM. Only CPU can.

0 David Dudley over 8 years ago in reply to Charles Tsai

Expert 1280 points

Guess I should have been a little more specific....

I keep forgetting there's a difference in this device between Flash and ROM.

My program and constant data is loaded into flash, but I can't use the DMA to transmit it out the SPI port.
I have no problem if I memcpy it into a ram buffer, and then send it out.

Would be more efficient and easier on memory consumption however, if I could just send it directly out of Flash.

David

0 Bob Crosby over 8 years ago in reply to David Dudley

TI__Guru 72500 points

David,

The DK-TM4C129X requires that the flash be enabled for DMA read. Try adding this code:

    //
    // Set up Flash Access for DMA
    //
    HWREG(FLASH_PP) |= FLASH_PP_DFA;
    HWREG(FLASH_DMASZ) = 0x4000;
    HWREG(FLASH_DMAST) = 0x0;

0 Bob Crosby over 8 years ago in reply to Bob Crosby

TI__Guru 72500 points

The macros are defined by:

#include "inc/hw_flash.h"

Arm-based microcontrollers

Arm-based microcontrollers forum

RTOS/DK-TM4C129X: DMA from Flash