PIC32 ADC with DMA problem

Hi,

I'm trying to load ADC samples to a buffer using DMA. So I set Timer 3 to trigger ADC convertions and once the convertion is complete it will trigger a DMA transfer. My objective is to load a buffer with all the ADC samples and once the buffer is complete I have to send it. My buffer is defined as "uint16_t buffer[20]".
So I set the DMA as follows:

    void *srcAddr  = (void *) &ADC1BUF0;
    void *destAddr = (void *) buffer

    DMAC_ChannelTransfer(DMAC_CHANNEL_1, srcAddr, 2, destAddr, sizeof(buffer), 2);

But all I get is the same sample being loaded in all of the buffers positions.

There is a register to set for the amount of data to send.
 
 

There is a register to set for the amount of data to send.

 
 //set up dma
 DCH0SSA = KVA_TO_PA(&PORTB); // Move the data from PORTB 
 DCH0DSA = KVA_TO_PA(&scopebuffercoherent);// Move the data to scopebuffer
 DCH0SSIZ = 2; // Source size is 2 bytes
 DCH0CSIZ = 2; // Move 2 bytes at a time
 DCH0DSIZ = scopebufferlength*2; // Move num_bytes bytes of data in total
 DCH0ECON=0; // Clear the DMA configuration settings 
 DCH0ECONbits.CHSIRQ = _TIMER_2_VECTOR; // Timer 2
 DCH0ECONbits.SIRQEN = 1; // Enable Start IRQ
 DCH0ECONbits.AIRQEN = 0; // Disable Abort IRQ
 
 DCH0CON = 0x83; // channel enabled, priority 3
 
 
 
 
 
 
// DCH0ECONbits.CFORCE=1;
 
 
 //wait until dma finished 
 if (!DCH0INTbits.CHDDIF)
 ;
 
 //copy to cached buffer
 unsigned int zx;
 for (zx=0;zx<scopebufferlength-1;zx++)
 {
 scopebuffer[zx]=scopebuffercoherent[zx]; 
 }
 

nigelwright7558
Also be careful with DMA'ed data as it is not cached so make buffer it goes into coherent.
 
unsigned short __attribute__((coherent)) scopebuffercoherent[scopebufferlength];
 
 

My PIC is a PIC32MX I thought that coherent attibute was for the MZ family only

nick23
 
My PIC is a PIC32MX I thought that coherent attibute was for the MZ family only

Or use volatile ?
 

You will probably have to set adc to continuous mode so it keeps getting a2d values.