Adjust examples

- Add examples for NRF52 I2S
- Move platform specific files into Platform folder

examples/Platforms/NRF52/NRF52_PDM_I2STest/NRF52_PDM_I2STest.ino

@@ -0,0 +1,39 @@
+#include <AutoAnalogAudio.h>
+
+AutoAnalog aaAudio;
+
+#if defined(USE_TINYUSB)
+    // Needed for Serial.print on non-MBED enabled or adafruit-based nRF52 cores
+    #include "Adafruit_TinyUSB.h"
+#endif
+
+/*********************************************************/
+/* Tested with MAX98357A I2S breakout
+/* BCLK connected to Arduino D1 (p0.03)
+/* LRCK connected to Arduino D3 (p0.29)
+/* DIN  connected to Arduino D5 (p0.05)
+/* SD   connected to Arduino D6 (p1.11)
+/*********************************************************/
+
+void setup() {
+
+
+  Serial.begin(115200);
+  aaAudio.begin(1, 1, 1);  //Setup aaAudio using DAC & I2S
+  aaAudio.adcBitsPerSample = 16; // 16-bit samples input from PDM
+  aaAudio.dacBitsPerSample = 16; // 16-bit samples output to I2S
+  aaAudio.setSampleRate(32000);  // 32kHz
+
+  pinMode(6, OUTPUT);  //Connected to SD pin of MAX98357A
+  digitalWrite(6,HIGH);
+
+}
+
+void loop() {
+
+  aaAudio.getADC(6400); // Get data from PDM microphone
+
+  memcpy(aaAudio.dacBuffer16, aaAudio.adcBuffer16, 12800); // Copy data into output buffer from input buffer
+
+  aaAudio.feedDAC(0,6400); // Feed the data to I2S output
+}

examples/Platforms/NRF52/NRF52_SD_Playback_I2S/NRF52_SD_Playback_I2S.ino

@@ -0,0 +1,94 @@
+/*
+    AutoAnalogAudio streaming via DAC & ADC by TMRh20
+    Copyright (C) 2016  TMRh20 - [email protected], github.com/TMRh20
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+  Auto Analog Audio (Automatic DAC, ADC & Timer) library
+
+  Auto Analog Audio Library Information:
+  http://github.com/TMRh20
+  http://tmrh20.blogspot.com
+
+*/
+
+#include <SPI.h>
+#include <SD.h>
+#include <AutoAnalogAudio.h>
+
+AutoAnalog aaAudio;
+
+/*********************************************************/
+/* Tested with MAX98357A I2S breakout
+/* BCLK connected to Arduino D1 (p0.03)
+/* LRCK connected to Arduino D3 (p0.29)
+/* DIN  connected to Arduino D5 (p0.05)
+/* SD   connected to Arduino D6 (p1.11)
+/*********************************************************/
+
+void setup() {
+
+  Serial.begin(115200);
+
+  Serial.print("Init SD card...");
+  if (!SD.begin(10000000, 2)) {
+    Serial.println("init failed!");
+    return;
+  }
+  Serial.println("init ok");
+  Serial.println("Analog Audio Begin");
+  aaAudio.begin(0, 1, 1);  //Setup aaAudio using DAC and I2S
+
+  //Setup for audio: Use 8 or 16-bit, mono or stereo. Valid sample rates are 16000, 24000, 32000, 44000
+  aaAudio.dacBitsPerSample = 8;    // 8-bit
+  aaAudio.setSampleRate(24000, 0); // 24khz, mono
+
+  pinMode(6,OUTPUT); //Connected to SD pin of MAX98357A
+  digitalWrite(6,HIGH);
+
+  playAudio("brick/brick24.wav"); // 24kHz @ 16-bits is about the maximum when reading from SD card
+}
+
+void loop() {
+
+  loadBuffer();
+
+}
+
+/*********************************************************/
+/* A simple function to handle playing audio files
+/*********************************************************/
+
+File myFile;
+
+void playAudio(char *audioFile) {
+
+  if (myFile) {
+    myFile.close();
+  }
+  //Open the designated file
+  myFile = SD.open(audioFile);
+  //Skip past the WAV header
+  myFile.seek(44);
+}
+
+void loadBuffer() {
+
+  if( myFile.available() ){
+    myFile.read(aaAudio.dacBuffer, 6400); // Change this to dacBuffer16 for 16-bit samples
+    aaAudio.feedDAC(0, 6400);             // change this to 3200 for 16-bit samples
+  }else{
+    myFile.seek(44);
+  }
+}