Adding support for SAM21 and other platforms

Author: nseidle

examples/Example1_Basic_Readings/Example1_Basic_Readings.ino

@@ -24,15 +24,18 @@
 
 MAX30105 particleSensor;
 
+#define debug Serial //Uncomment this line if you're using an Uno or ESP
+//#define debug SerialUSB //Uncomment this line if you're using a SAMD21
+
 void setup()
 {
-  Serial.begin(115200);
-  Serial.println("Initializing...");
+  debug.begin(115200);
+  debug.println("Initializing...");
 
   // Initialize sensor
   if (!particleSensor.begin(Wire, I2C_SPEED_FAST)) //Use default I2C port, 400kHz speed
   {
-    Serial.println("MAX30105 was not found. Please check wiring/power. ");
+    debug.println("MAX30105 was not found. Please check wiring/power. ");
     while (1);
   }
 
@@ -41,13 +44,13 @@ void setup()
 
 void loop()
 {
-  Serial.print(" R[");
-  Serial.print(particleSensor.getRed());
-  Serial.print("] IR[");
-  Serial.print(particleSensor.getIR());
-  Serial.print("] G[");
-  Serial.print(particleSensor.getGreen());
-  Serial.print("]");
-
-  Serial.println();
+  debug.print(" R[");
+  debug.print(particleSensor.getRed());
+  debug.print("] IR[");
+  debug.print(particleSensor.getIR());
+  debug.print("] G[");
+  debug.print(particleSensor.getGreen());
+  debug.print("]");
+
+  debug.println();
 }

src/MAX30105.cpp

@@ -619,19 +619,19 @@ uint16_t MAX30105::check(void)
     _i2cPort->write(MAX30105_FIFODATA);
     _i2cPort->endTransmission();
 
+    //We may need to read as many as 288 bytes so we read in blocks no larger than I2C_BUFFER_LENGTH
+    //I2C_BUFFER_LENGTH changes based on the platform. 64 bytes for SAMD21, 32 bytes for Uno.
     //Wire.requestFrom() is limited to BUFFER_LENGTH which is 32 on the Uno
-    //We may need to read as many as 288 bytes so we read in blocks no larger than 32
-    //BUFFER_LENGTH should work with other platforms with larger requestFrom buffers
     while (bytesLeftToRead > 0)
     {
       int toGet = bytesLeftToRead;
-      if (toGet > BUFFER_LENGTH)
+      if (toGet > I2C_BUFFER_LENGTH)
       {
         //If toGet is 32 this is bad because we read 6 bytes (Red+IR * 3 = 6) at a time
         //32 % 6 = 2 left over. We don't want to request 32 bytes, we want to request 30.
         //32 % 9 (Red+IR+GREEN) = 5 left over. We want to request 27.
 
-        toGet = BUFFER_LENGTH - (BUFFER_LENGTH % (activeLEDs * 3)); //Trim toGet to be a multiple of the samples we need to read
+        toGet = I2C_BUFFER_LENGTH - (I2C_BUFFER_LENGTH % (activeLEDs * 3)); //Trim toGet to be a multiple of the samples we need to read
       }
 
       bytesLeftToRead -= toGet;

src/MAX30105.h

@@ -25,6 +25,24 @@
 #define I2C_SPEED_STANDARD        100000
 #define I2C_SPEED_FAST            400000
 
+//Define the size of the I2C buffer based on the platform the user has
+#if defined(__AVR_ATmega328P__) || defined(__AVR_ATmega168__)
+
+  //I2C_BUFFER_LENGTH is defined in Wire.H
+  #define I2C_BUFFER_LENGTH BUFFER_LENGTH
+
+#elif defined(__SAMD21G18A__)
+
+  //SAMD21 uses RingBuffer.h
+  #define I2C_BUFFER_LENGTH SERIAL_BUFFER_SIZE
+
+#else
+
+  //The catch-all default is 32
+  #define I2C_BUFFER_LENGTH 32
+
+#endif
+
 class MAX30105 {
  public: 
   MAX30105(void);