3 Replies Latest reply on Aug 10, 2020 10:01 AM by WaMa_286156

    How to DMA From SRAM to Control Reg At 100khz rate? help, please.

    WaMa_286156

      I am trying to DMA from an SRAM array into a Control Register at a 100khz rate. (See attached project)

       

      I am building under PSoC Creator 4.2, but also tried it under 4.3. Same results either version of Creator.

       

      According to this post (DMA to GPIO ) feeding a clock into DRQ should work at the clock rate.  As you can see from this image here, once started, the DMA keeps transferring at a high rate ( appears to be about 3mhz).  I am sending 4 bytes,  0,1,2,3 out the control register over and over.

       

      I want the DMA to start over automatically, and transfer at the DRQ rate over and over, re-running the array each time.  (The Preserve parameter is set to 1 for this, and it appears to be working.)

       

      dmaShiftreg.jpeg

       

      The Bytes per burst and request per burst are both 1 (from the DMA wizard):

       

      #define DMA_1_BYTES_PER_BURST 1

      #define DMA_1_REQUEST_PER_BURST 1

      #define DMA_1_SRC_BASE (CYDEV_SRAM_BASE)

      #define DMA_1_DST_BASE (CYDEV_PERIPH_BASE)

       

       

      /* Variable declarations for DMA_1 */

      /* Move these variable declarations to the top of the function */

      uint8 DMA_1_Chan;

      uint8 DMA_1_TD[1];

      void DMA_1_Start() {

          /* DMA Configuration for DMA_1 */

          DMA_1_Chan = DMA_1_DmaInitialize(DMA_1_BYTES_PER_BURST, DMA_1_REQUEST_PER_BURST,

              HI16(DMA_1_SRC_BASE), HI16(DMA_1_DST_BASE));

          DMA_1_TD[0] = CyDmaTdAllocate();

          CyDmaTdSetConfiguration(DMA_1_TD[0], 4, DMA_1_TD[0], DMA_1__TD_TERMOUT_EN | CY_DMA_TD_INC_SRC_ADR | CY_DMA_TD_AUTO_EXEC_NEXT);

          CyDmaTdSetAddress(DMA_1_TD[0], LO16((uint32)OutData), LO16((uint32)crPulsesOut_Control_PTR));

          CyDmaChSetInitialTd(DMA_1_Chan, DMA_1_TD[0]);

          CyDmaChEnable(DMA_1_Chan, 1);

      }

       

      Can someone help me with this?