SERCOM stuff - simplify, cleanup, add SAMD21 dummy funcs

Author: PaintYourDragon

cores/arduino/SERCOM.cpp

@@ -751,6 +751,9 @@ int8_t SERCOM::getSercomIndex(void) {
 // This is currently for overriding an SPI SERCOM's clock source only --
 // NOT for UART or WIRE SERCOMs, where it will have unintended consequences.
 // It does not check.
+// SERCOM clock source override is available only on SAMD51 (not 21).
+// A dummy function for SAMD21 (compiles to nothing) is present in SERCOM.h
+// so user code doesn't require a lot of conditional situations.
 void SERCOM::setClockSource(int8_t idx, SercomClockSource src, bool core) {
 
   if(src == SERCOM_CLOCK_SOURCE_NO_CHANGE) return;
@@ -794,7 +797,6 @@ void SERCOM::setClockSource(int8_t idx, SercomClockSource src, bool core) {
 }
 #endif
 
-
 void SERCOM::initClockNVIC( void )
 {
   int8_t idx = getSercomIndex();
@@ -808,8 +810,9 @@ void SERCOM::initClockNVIC( void )
     NVIC_EnableIRQ(sercomData[idx].irq[i]);
   }
 
-  // SPI DMA speed is dictated by the "slow clock," so BOTH are set to the
-  // same clock source (clk_slow isn't sourced from XOSC32K as before).
+  // SPI DMA speed is dictated by the "slow clock" (I think...maybe) so
+  // BOTH are set to the same clock source (clk_slow isn't sourced from
+  // XOSC32K as in prior versions of SAMD core).
   // This might have power implications for sleep code.
 
   setClockSource(idx, clockSource, true);  // true  = core clock

cores/arduino/SERCOM.h

@@ -152,7 +152,10 @@ typedef enum
 	WIRE_MASTER_NACK_ACTION
 } SercomMasterAckActionWire;
 
-#if defined(__SAMD51__)
+// SERCOM clock source override is available only on SAMD51 (not 21)
+// but the enumeration is made regardless so user code doesn't need
+// ifdefs or lengthy comments explaining the different situations --
+// the clock-sourcing functions just compile to nothing on SAMD21.
 typedef enum SercomClockSource {
   SERCOM_CLOCK_SOURCE_FCPU,     // F_CPU clock (GCLK0)
   SERCOM_CLOCK_SOURCE_48M,      // 48 MHz peripheral clock (GCLK1) (standard)
@@ -161,7 +164,6 @@ typedef enum SercomClockSource {
   SERCOM_CLOCK_SOURCE_12M,      // 12 MHz peripheral clock (GCLK4)
   SERCOM_CLOCK_SOURCE_NO_CHANGE // Leave clock source setting unchanged
 };
-#endif // end __SAMD51__
 
 class SERCOM
 {
@@ -233,16 +235,26 @@ class SERCOM
 		uint8_t readDataWIRE( void ) ;
 		int8_t getSercomIndex(void);
 #if defined(__SAMD51__)
+		// SERCOM clock source override is only available on
+		// SAMD51 (not 21) ... but these functions are declared
+		// regardless so user code doesn't need ifdefs or lengthy
+		// comments explaining the different situations -- these
+		// just compile to nothing on SAMD21.
 		void setClockSource(int8_t idx, SercomClockSource src, bool core);
 		SercomClockSource getClockSource(void) { return clockSource; };
 		uint32_t getFreqRef(void) { return freqRef; };
+#else
+		// The equivalent SAMD21 dummy functions...
+		void setClockSource(int8_t idx, SercomClockSource src, bool core) { };
+		SercomClockSource getClockSource(void) { return SERCOM_CLOCK_SOURCE_FCPU; };
+		uint32_t getFreqRef(void) { return F_CPU; };
 #endif
 
 	private:
 		Sercom* sercom;
 #if defined(__SAMD51__)
                 SercomClockSource clockSource;
-                uint32_t freqRef;
+                uint32_t freqRef; // Frequency corresponding to clockSource
 #endif
 		uint8_t calculateBaudrateSynchronous(uint32_t baudrate);
 		uint32_t division(uint32_t dividend, uint32_t divisor) ;

libraries/SPI/SPI.cpp

@@ -42,10 +42,6 @@ SPIClass::SPIClass(SERCOM *p_sercom, uint8_t uc_pinMISO, uint8_t uc_pinSCK, uint
   // SERCOM pads
   _padTx=PadTx;
   _padRx=PadRx;
-
-#if defined(__SAMD51__)
-  maxBitrate = MAX_SPI; // Can override via setClockSource()
-#endif
 }
 
 void SPIClass::begin()
@@ -247,7 +243,6 @@ void SPIClass::detachInterrupt() {
   // Should be disableInterrupt()
 }
 
-#if defined(__SAMD21__) || defined(__SAMD51__)
 // SPI DMA lookup works on both SAMD21 and SAMD51
 
 volatile uint32_t *SPIClass::getDataRegister(void) {
@@ -282,16 +277,17 @@ int SPIClass::getDMACID(void) {
   return (idx >= 0) ? DMACID[idx] : -1;
 }
 
-#endif // end __SAMD21__ || __SAMD51__
-
 #if defined(__SAMD51__)
 
-// Set the SPI device's SERCOM clock CORE and/or SLOW clock source(s).
-// These are SercomClockSource values from an enumeration in SERCOM.h.
-void SPIClass::setClockSources(SercomClockSource core, SercomClockSource slow) {
+// Set the SPI device's SERCOM clock CORE and SLOW clock sources.
+// SercomClockSource values are an enumeration in SERCOM.h.
+// This works on SAMD51 only.  On SAMD21, a dummy function is declared
+// in SPI.h which compiles to nothing, so user code doesn't need to check
+// and conditionally compile lines for different architectures.
+void SPIClass::setClockSource(SercomClockSource clk) {
   int8_t idx = _p_sercom->getSercomIndex();
-  _p_sercom->setClockSource(idx, core, true);  // true  = set core clock
-  _p_sercom->setClockSource(idx, slow, false); // false = set slow clock
+  _p_sercom->setClockSource(idx, clk, true);  // true  = set core clock
+  _p_sercom->setClockSource(idx, clk, false); // false = set slow clock
 }
 
 #endif // end __SAMD51__

libraries/SPI/SPI.h

@@ -41,7 +41,7 @@
   // SAMD51 has configurable MAX_SPI, else use peripheral clock default.
   // Update: changing MAX_SPI via compiler flags is DEPRECATED, because
   // this affects ALL SPI peripherals including some that should NOT be
-  // changed (e.g. anything using SD card). Use the setClockSources()
+  // changed (e.g. anything using SD card). Use the setClockSource()
   // function instead. This is left here for compatibility with interim code.
   #if !defined(MAX_SPI)
     #define MAX_SPI 24000000
@@ -107,17 +107,6 @@ class SPISettings {
   friend class SPIClass;
 };
 
-#if defined(__SAMD51__)
-enum SPIClockSource {
-  SPI_CLOCK_SOURCE_NO_CHANGE, // Leave clock source setting unchanged
-  SPI_CLOCK_SOURCE_FCPU,      // F_CPU clock (GCLK0)
-  SPI_CLOCK_SOURCE_48M,       // 48 MHz peripheral clock (GCLK1) (standard)
-  SPI_CLOCK_SOURCE_100M,      // 100 MHz peripheral clock (GCLK2)
-  SPI_CLOCK_SOURCE_32K,       // XOSC32K clock (GCLK3)
-  SPI_CLOCK_SOURCE_12M        // 12 MHz peripheral clock (GCLK4)
-};
-#endif // end __SAMD51__
-
 class SPIClass {
   public:
   SPIClass(SERCOM *p_sercom, uint8_t uc_pinMISO, uint8_t uc_pinSCK, uint8_t uc_pinMOSI, SercomSpiTXPad, SercomRXPad);
@@ -143,15 +132,17 @@ class SPIClass {
   void setDataMode(uint8_t uc_mode);
   void setClockDivider(uint8_t uc_div);
 
-#if defined(__SAMD21__) || defined(__SAMD51__)
+  // SERCOM lookup functions are available on both SAMD51 and 21.
   volatile uint32_t *getDataRegister(void);
-  int                getDMACID(void);
-#endif
+  int getDMACID(void);
+  uint8_t getSercomIndex(void) { return _p_sercom->getSercomIndex(); };
 #if defined(__SAMD51__)
-  void               setClockSources(
-                       SercomClockSource core = SERCOM_CLOCK_SOURCE_NO_CHANGE,
-                       SercomClockSource slow = SERCOM_CLOCK_SOURCE_NO_CHANGE);
-  uint32_t           getMaxBitrate(void) { return maxBitrate; };
+  // SERCOM clock source override is available only on SAMD51.
+  void setClockSource(SercomClockSource clk);
+#else
+  // On SAMD21, this compiles to nothing, so user code doesn't need to
+  // check and conditionally compile lines for different architectures.
+  void setClockSource(SercomClockSource clk) { };
 #endif // end __SAMD51__
 
   private:
@@ -170,9 +161,6 @@ class SPIClass {
   uint8_t interruptMode;
   char interruptSave;
   uint32_t interruptMask;
-#if defined(__SAMD51__)
-  uint32_t maxBitrate;
-#endif
 };
 
 #if SPI_INTERFACES_COUNT > 0