Restore RAK18000 examples.

examples/RAK11300/IO/RAK18000_Stereo/RAK18000_Stereo.ino

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+/**
+ * @file RAK18000_Stereo.ino
+ * @author rakwireless
+ * @brief  This example reads audio data from the on-board PDM microphones, and prints
+ * out the samples to the Serial console. The Serial Plotter built into the
+ * Arduino IDE can be used to plot the audio data (Tools -> Serial Plotter)
+ * @version 0.1
+ * @date 2021-03-07
+ *
+ * @copyright Copyright (c) 2020
+ *
+ */
+
+#include <PDM.h>
+
+// buffer to read samples into, each sample is 16-bits
+short sampleBuffer[256] = {0};
+
+// number of samples read
+volatile int samplesRead = 0;
+
+void setup() {
+
+	time_t timeout = millis();
+	Serial.begin(115200);
+	while (!Serial)
+	{
+		if ((millis() - timeout) < 5000)
+		{
+			delay(100);
+		}
+		else
+		{
+			break;
+		}
+	}
+
+  PDM.setBufferSize(256);
+  // configure the data receive callback
+  PDM.onReceive(onPDMdata);
+  // optionally set the gain, defaults to 20
+  PDM.setGain(20);
+
+  // initialize PDM with:
+  // - 2 means stereo, 1 means single
+  // - a 16 kHz sample rate
+  if (!PDM.begin(2, 16000)) 
+  {
+    Serial.println("Failed to start PDM!");
+    while (1);
+  }
+}
+
+void loop() 
+{
+    for (int i = 0; i < samplesRead; i++) 
+    {
+        //Simple filtering, if less than 200, it will be regarded as noise
+        if(sampleBuffer[i] <= 200 && sampleBuffer[i] >= -200)
+        {
+            sampleBuffer[i] = 0;
+        } 
+        Serial.println(sampleBuffer[i]);
+    }
+    // clear the read count
+	  samplesRead = 0;
+}
+
+void onPDMdata() {
+  // query the number of bytes available
+  int bytesAvailable = PDM.available();
+
+  // read into the sample buffer
+  PDM.read((uint8_t *)sampleBuffer, bytesAvailable);
+  // 16-bit, 2 bytes per sample
+  samplesRead = bytesAvailable/2;
+}

examples/RAK4630/IO/RAK18000_Stereo/RAK18000_Stereo.ino

@@ -0,0 +1,94 @@
+/**
+ * @file RAK18000_Stereo.ino
+ * @author rakwireless
+ * @brief  This example reads audio data from the on-board PDM microphones, and prints
+ * out the samples to the Serial console. The Serial Plotter built into the
+ * Arduino IDE can be used to plot the audio data (Tools -> Serial Plotter)
+ * @version 0.1
+ * @date 2021-03-07
+ *
+ * @copyright Copyright (c) 2020
+ *
+ * @note RAK4631 GPIO mapping to nRF52840 GPIO ports
+   RAK4631    <->  nRF52840
+   WB_IO1     <->  P0.17 (GPIO 17)
+   WB_IO2     <->  P1.02 (GPIO 34)
+   WB_IO3     <->  P0.21 (GPIO 21)
+   WB_IO4     <->  P0.04 (GPIO 4)
+   WB_IO5     <->  P0.09 (GPIO 9)
+   WB_IO6     <->  P0.10 (GPIO 10)
+   WB_SW1     <->  P0.01 (GPIO 1)
+   WB_A0      <->  P0.04/AIN2 (AnalogIn A2)
+   WB_A1      <->  P0.31/AIN7 (AnalogIn A7)
+ */
+#include <Wire.h>
+
+#include <PDM.h>
+
+#define PDM_DATA_PIN  21
+#define PDM_CLK_PIN   4
+#define PDM_PWR_PIN   -1
+
+// buffer to read samples into, each sample is 16-bits
+short sampleBuffer[256] = {0};
+
+// number of samples read
+volatile int samplesRead = 0;
+
+void setup() {
+
+	time_t timeout = millis();
+	Serial.begin(115200);
+	while (!Serial)
+	{
+		if ((millis() - timeout) < 5000)
+		{
+			delay(100);
+		}
+		else
+		{
+			break;
+		}
+	}
+
+  PDM.setPins(PDM_DATA_PIN, PDM_CLK_PIN, PDM_PWR_PIN);
+  PDM.setBufferSize(256);
+  // configure the data receive callback
+  PDM.onReceive(onPDMdata);
+  // optionally set the gain, defaults to 20
+  PDM.setGain(20);
+
+  // initialize PDM with:
+  // - 2 means stereo, 1 means single
+  // - a 16 kHz sample rate
+  if (!PDM.begin(2, 16000)) 
+  {
+    Serial.println("Failed to start PDM!");
+    while (1);
+  }
+}
+
+void loop() 
+{
+    for (int i = 0; i < samplesRead; i++) 
+    {
+        //Simple filtering, if less than 200, it will be regarded as noise
+        if(sampleBuffer[i] <= 200 && sampleBuffer[i] >= -200)
+        {
+            sampleBuffer[i] = 0;
+        } 
+        Serial.println(sampleBuffer[i]);
+    }
+    // clear the read count
+	  samplesRead = 0;
+}
+
+void onPDMdata() {
+  // query the number of bytes available
+  int bytesAvailable = PDM.available();
+
+  // read into the sample buffer
+  PDM.read((uint8_t *)sampleBuffer, bytesAvailable);
+  // 16-bit, 2 bytes per sample
+  samplesRead = bytesAvailable/2;
+}