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Patriks
Patriks
Senior
February 3, 2015
Solved

Continous data transfer to GPIO with DMA SPC56EL

  • February 3, 2015
  • 1 reply
  • 652 views
Posted on February 03, 2015 at 16:11

Hello,

I would like to use DMA to control the states of some GPIOs. The software should write the entries of an array to the PGPDO[0]register. For that case, I wrote a small demo program. The outputArray isuint16_t and contains 256 elements.Each element stands for a state of 8 GPIO pins. The software should write these elements circular to the PGPDO[0] register, but it doesn´t work. The configuration looks like that: 

 edmaChannelStart(0); 
edmaTCDSetWord0(edmaGetTCD(0),&outputArray); 
edmaTCDSetWord1(edmaGetTCD(0),1,1,2); 
edmaTCDSetWord2(edmaGetTCD(0),512); 
edmaTCDSetWord3(edmaGetTCD(0),-512); 
edmaTCDSetWord4(edmaGetTCD(0),&SIUL.PGPDO[0].R); 
edmaTCDSetWord5Linked(edmaGetTCD(0),0,0xFF,1); 
edmaTCDSetWord6(edmaGetTCD(0),0); 
edmaTCDSetWord7Linked(edmaGetTCD(0),0,0xFF,EDMA_TCD_MODE_START);

Can anybody tell me what I have to change in my configuration when I want the DMA transfer to run continuously as fast as possible? Best regards, Patrik
    This topic has been closed for replies.
    Best answer by Patriks
    Posted on February 05, 2015 at 16:06

    Hello,

    I have found the problem. I think it was a combination of wrong channel config and DMA_MUX config. The following code gives me a continuous transfer of the array elements to the PGPDO port. The DAC2Table contains 128 16bit elemements. 

    
 DMAMUX.CHCONFIG[3].R = 0x00; 
DMAMUX.CHCONFIG[3].R = 0b10001110; 
EDMA.DMAERQL.R = 0xFFFF; 
edmaChannelSetup(3,&DAC2Table,&SIUL.PGPDO[0].R,2,0,1,1,2,128,-256,0,EDMA_TCD_MODE_START);

    I was also able to trigger the transfer of an array element using PIT and the triggered functionality. Nevertheless, I have again some problems in understanding how to use DMA with other modules. It is really hard to get detailed information out of the reference manual and I didn´t found any application notes for the SPC56EL regarding this topic. In DMA_MUX section, I saw the possibility to use the eTimer module as DMA source. Table 173 shows two sources for eTimer_0 - Channel0 and Channel1. But what does this mean? What kind of request connects the eTimer to DMA?Are they regarding to the capture and compare registers? And how do I use the eTimer in combination with DMA? What I want to do is to trigger the transfer ofan array element when theeTimer produces a compare event. The eTimer should reload the load the new compare value from the compare load register, which should then be updated by DMA. Best regards, Patrik

    1 reply

    Patriks
    PatriksAuthorBest answer
    Senior
    February 5, 2015
    Posted on February 05, 2015 at 16:06

    Hello,

    I have found the problem. I think it was a combination of wrong channel config and DMA_MUX config. The following code gives me a continuous transfer of the array elements to the PGPDO port. The DAC2Table contains 128 16bit elemements. 

    
 DMAMUX.CHCONFIG[3].R = 0x00; 
DMAMUX.CHCONFIG[3].R = 0b10001110; 
EDMA.DMAERQL.R = 0xFFFF; 
edmaChannelSetup(3,&DAC2Table,&SIUL.PGPDO[0].R,2,0,1,1,2,128,-256,0,EDMA_TCD_MODE_START);

    I was also able to trigger the transfer of an array element using PIT and the triggered functionality. Nevertheless, I have again some problems in understanding how to use DMA with other modules. It is really hard to get detailed information out of the reference manual and I didn´t found any application notes for the SPC56EL regarding this topic. In DMA_MUX section, I saw the possibility to use the eTimer module as DMA source. Table 173 shows two sources for eTimer_0 - Channel0 and Channel1. But what does this mean? What kind of request connects the eTimer to DMA?Are they regarding to the capture and compare registers? And how do I use the eTimer in combination with DMA? What I want to do is to trigger the transfer ofan array element when theeTimer produces a compare event. The eTimer should reload the load the new compare value from the compare load register, which should then be updated by DMA. Best regards, Patrik
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