initial commit

libraries/Adafruit_Zero_DMA_Library/examples/zerodma_memcpy/zerodma_memcpy.ino

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+// Simple ZeroDMA example -- an equivalent to the memcpy() function.
+// Decause it uses DMA, unlike memcpy(), your code could be doing other
+// things simultaneously while the copy operation runs.
+
+#include <Adafruit_ZeroDMA.h>
+#include "utility/dma.h"
+
+Adafruit_ZeroDMA myDMA;
+ZeroDMAstatus    stat; // DMA status codes returned by some functions
+
+// The memory we'll be moving:
+#define DATA_LENGTH 1024
+uint8_t source_memory[DATA_LENGTH],
+        destination_memory[DATA_LENGTH];
+
+volatile bool transfer_is_done = false; // Done yet?
+
+// Callback for end-of-DMA-transfer
+void dma_callback(Adafruit_ZeroDMA *dma) {
+  (void) dma;
+  transfer_is_done = true;
+}
+
+void setup() {
+  uint32_t t;
+  pinMode(LED_BUILTIN, OUTPUT);   // Onboard LED can be used for precise
+  digitalWrite(LED_BUILTIN, LOW); // benchmarking with an oscilloscope
+  Serial.begin(115200);
+  while(!Serial);                 // Wait for Serial monitor before continuing
+
+  Serial.println("DMA test: memory copy");
+
+  Serial.print("Allocating DMA channel...");
+  stat = myDMA.allocate();
+  myDMA.printStatus(stat);
+
+  Serial.println("Setting up transfer");
+  myDMA.addDescriptor(source_memory, destination_memory, DATA_LENGTH);
+
+  Serial.println("Adding callback");
+  // register_callback() can optionally take a second argument
+  // (callback type), default is DMA_CALLBACK_TRANSFER_DONE
+  myDMA.setCallback(dma_callback);
+
+  // Fill the source buffer with incrementing bytes, dest buf with 0's
+  for(uint32_t i=0; i<DATA_LENGTH; i++) source_memory[i] = i;
+  memset(destination_memory, 0, DATA_LENGTH);
+
+  // Show the destination buffer is empty before transfer
+  Serial.println("Destination buffer before transfer:");
+  dump();
+
+  Serial.println("Starting transfer job");
+  stat = myDMA.startJob();
+  myDMA.printStatus(stat);
+
+  Serial.println("Triggering DMA transfer...");
+  t = micros();
+  digitalWrite(LED_BUILTIN, HIGH);
+  myDMA.trigger();
+
+  // Your code could do other things here while copy happens!
+
+  while(!transfer_is_done); // Chill until DMA transfer completes
+
+  digitalWrite(LED_BUILTIN, LOW);
+  t = micros() - t; // Elapsed time
+
+  Serial.print("Done! ");
+  Serial.print(t);
+  Serial.println(" microseconds");
+
+  Serial.println("Destination buffer after transfer:");
+  dump();
+
+  // Now repeat the same operation, but 'manually' using memcpy() (not DMA):
+  t = micros();
+  digitalWrite(LED_BUILTIN, HIGH);
+  memcpy(destination_memory, source_memory,  DATA_LENGTH);
+  digitalWrite(LED_BUILTIN, LOW);
+  t = micros() - t; // Elapsed time
+  Serial.print("Same operation without DMA: ");
+  Serial.print(t);
+  Serial.println(" microseconds");
+}
+
+// Show contents of destination_memory[] array
+void dump() {
+  for(uint32_t i=0; i<DATA_LENGTH; i++) {
+    Serial.print(destination_memory[i], HEX); Serial.print(' ');
+    if ((i & 15) == 15) Serial.println();
+  }
+}
+
+void loop() { }