initial commit

libraries/Adafruit_Zero_DMA_Library/examples/zerodma_spi1/zerodma_spi1.ino

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+// DMA-based SPI buffer write.  This is transmit-only as written, i.e.
+// not equivalent to Arduino's SPI.transfer() which both sends and
+// receives a single byte or word.  Also, this is single-buffered to
+// demonstrate a simple SPI write case.  See zerodma_spi2.ino for an
+// example using double buffering (2 buffers alternating fill & transmit).
+
+#include <SPI.h>
+#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 issuing to SPI:
+#define DATA_LENGTH 2048
+uint8_t source_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: SPI data out");
+
+  SPI.begin();
+
+  Serial.println("Configuring DMA trigger");
+#ifdef __SAMD51__
+  // SERCOM2 is the 'native' SPI SERCOM on Metro M4
+  myDMA.setTrigger(SERCOM2_DMAC_ID_TX);
+#else
+  // SERCOM4 is the 'native' SPI SERCOM on most M0 boards
+  myDMA.setTrigger(SERCOM4_DMAC_ID_TX);
+#endif
+  myDMA.setAction(DMA_TRIGGER_ACTON_BEAT);
+
+  Serial.print("Allocating DMA channel...");
+  stat = myDMA.allocate();
+  myDMA.printStatus(stat);
+
+  Serial.println("Setting up transfer");
+  myDMA.addDescriptor(
+    source_memory,                    // move data from here
+#ifdef __SAMD51__
+    (void *)(&SERCOM2->SPI.DATA.reg), // to here (M4)
+#else
+    (void *)(&SERCOM4->SPI.DATA.reg), // to here (M0)
+#endif
+    DATA_LENGTH,                      // this many...
+    DMA_BEAT_SIZE_BYTE,               // bytes/hword/words
+    true,                             // increment source addr?
+    false);                           // increment dest addr?
+
+  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
+  for(uint32_t i=0; i<DATA_LENGTH; i++) source_memory[i] = i;
+
+  // Start SPI transaction at 12 MHz
+  SPI.beginTransaction(SPISettings(12000000, MSBFIRST, SPI_MODE0));
+
+  Serial.println("Starting transfer job");
+  t = micros();
+  digitalWrite(LED_BUILTIN, HIGH);
+
+  // Because we've configured a peripheral trigger (SPI), there's
+  // no need to manually trigger transfer, it starts up on its own.
+  stat = myDMA.startJob();
+
+  // Your code could do other things here while SPI write happens!
+
+  while(!transfer_is_done); // Chill until DMA transfer completes
+
+  digitalWrite(LED_BUILTIN, LOW);
+  t = micros() - t; // Elapsed time
+
+  SPI.endTransaction();
+  myDMA.printStatus(stat); // Results of start_transfer_job()
+
+  Serial.print("Done! ");
+  Serial.print(t);
+  Serial.println(" microseconds");
+}
+
+void loop() { }