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libraries/audio-tools/examples/sandbox/spi/spi-slave-esp32/spi-slave-esp32.ino

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+/***
+ * We use the ESP32DMASPISlave library to implement the SPI slave on the ESP32
+ * which receives the data
+ * 
+ * Untested DRAFT implementation!
+ */
+#include <ESP32DMASPISlave.h>
+#include "AudioTools.h"
+
+const size_t BUFFER_SIZE = 1024;
+uint8_t *dma_rx_buf;
+ESP32DMASPI::Slave spi_slave;
+AudioInfo info(44100, 2, 16); //
+I2SStream out; // or replace with another output
+
+void setup() {
+  Serial.begin(115200);
+  // setup I2S
+  auto cfg = out.defaultConfig(TX_MODE);
+  cfg.copyFrom(info);
+  //cfg.pin_bck = 14;
+  //cfg.pin_ws = 15;
+  //cfg.pin_data = 22;
+  // to use DMA buffer, use these methods to allocate buffer
+  dma_rx_buf = spi_slave.allocDMABuffer(BUFFER_SIZE);
+
+  spi_slave.setDataMode(SPI_MODE0);           // default: SPI_MODE0
+  spi_slave.setMaxTransferSize(BUFFER_SIZE);  // default: 4092 bytes
+
+  // begin() after setting
+  spi_slave.begin();  // default: HSPI (please refer README for pin assignments)
+
+}
+
+void loop() {
+  // start and wait to complete one BIG transaction
+  size_t received_bytes = spi_slave.transfer(nullptr, dma_rx_buf, BUFFER_SIZE);
+  out.write(dma_rx_buf, received_bytes);
+}