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ZeroDMA: Allocate descriptors from local buffer #247

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ZeroDMA: Allocate descriptors from local buffer #247

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13 changes: 11 additions & 2 deletions libraries/Adafruit_ZeroDMA/Adafruit_ZeroDMA.cpp
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
#include <Adafruit_ZeroDMA.h>
#include <malloc.h> // memalign() function

#include "utility/dma.h"
static volatile uint32_t _channelMask = 0; // Bitmask of allocated channels
Expand Down Expand Up @@ -477,7 +476,7 @@ DmacDescriptor *Adafruit_ZeroDMA::addDescriptor(
// (aligned_alloc() or posix_memalign()) are not currently
// available in the version of ARM GCC in use, but this is,
// so here we are.
if(!(desc = (DmacDescriptor *)memalign(16, sizeof(DmacDescriptor)))) {
if(!(desc = alloc_descriptor())) {
return NULL;
}
DmacDescriptor *prev = &_descriptor[channel];
Expand Down Expand Up @@ -613,6 +612,16 @@ void Adafruit_ZeroDMA::loop(boolean flag) {
}
}

//Alocates a descriptor from the local pool
DmacDescriptor * Adafruit_ZeroDMA::alloc_descriptor(){
if(allocated * sizeof(DmacDescriptor) >= sizeof(desc_heap)){
return (DmacDescriptor *)(&desc_heap[0] + (allocated++) * sizeof(DmacDescriptor));
}else
{
return NULL;
}
}

// MISCELLANY --------------------------------------------------------------

void Adafruit_ZeroDMA::printStatus(ZeroDMAstatus s) const {
Expand Down
7 changes: 7 additions & 0 deletions libraries/Adafruit_ZeroDMA/Adafruit_ZeroDMA.h
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,10 @@
#include "Arduino.h"
#include "utility/dma.h"

#ifndef DMAC_DESC_HEAP_SIZE
#define DMAC_DESC_HEAP_SIZE 4
#endif

// Status codes returned by some DMA functions and/or held in
// a channel's jobStatus variable.
enum ZeroDMAstatus {
Expand Down Expand Up @@ -54,13 +58,16 @@ class Adafruit_ZeroDMA {


protected:
__attribute__((__aligned__(16))) uint8_t desc_heap[DMAC_DESC_HEAP_SIZE*16];
DmacDescriptor * alloc_descriptor();
uint8_t channel;
volatile enum ZeroDMAstatus jobStatus;
bool hasDescriptors;
bool loopFlag;
uint8_t peripheralTrigger;
dma_transfer_trigger_action triggerAction;
void (*callback[DMA_CALLBACK_N])(Adafruit_ZeroDMA *);
size_t allocated = 0;
};

#endif // _ADAFRUIT_ZERODMA_H_