avoid float division

Author: hathach

cores/arduino/SERCOM.cpp

@@ -479,15 +479,16 @@ void SERCOM::initMasterWIRE( uint32_t baudrate )
 //  sercom->I2CM.INTENSET.reg = SERCOM_I2CM_INTENSET_MB | SERCOM_I2CM_INTENSET_SB | SERCOM_I2CM_INTENSET_ERROR ;
 
   uint8_t speedBit = sercom->I2CM.CTRLA.bit.SPEED;
-  uint32_t topSpeeds[3] = {400000, 1000000, 3400000}; // {(sm/fm), (fm+), (hs)}
+  const uint32_t topSpeeds[3] = {400000, 1000000, 3400000}; // {(sm/fm), (fm+), (hs)}
   const uint32_t minBaudrate = freqRef / 512;         // BAUD = 255: SAMD51 ~195kHz, SAMD21 ~94kHz
   const uint32_t maxBaudrate = topSpeeds[speedBit];
   baudrate = max(minBaudrate, min(baudrate, maxBaudrate));
 
   if (speedBit == 0x2)
     sercom->I2CM.BAUD.bit.HSBAUD = freqRef / (2 * baudrate) - 1;
   else
-    sercom->I2CM.BAUD.bit.BAUD = freqRef / (2 * baudrate) - 5 - freqRef * WIRE_RISE_TIME_NANOSECONDS / (2 * 1e9f);
+    sercom->I2CM.BAUD.bit.BAUD = freqRef / (2 * baudrate) - 5 -
+      (freqRef/2000000ul * WIRE_RISE_TIME_NANOSECONDS) / 1000;
 }
 
 void SERCOM::prepareNackBitWIRE( void )
@@ -789,10 +790,15 @@ uint32_t SERCOM::getSercomFreqRef(void)
     gen = GCLK->PCHCTRL[pch].bit.GEN;
   }
 
+  // GCLK0 = F_CPU
+  // GCLK1 = 48 MHz
+  // GCLK2 = 100 MHz
+  // GCLK3 = XOSC32K
+  // GCLK4 = 12 MHz
   switch (gen)
   {
   case 0:
-    freqRef = 100000000UL;
+    freqRef = 100000000UL; // F_CPU but limit at 100 Mhz for SERCOM ref clock
     break;
   case 1:
     freqRef = 48000000UL;
@@ -836,7 +842,7 @@ void SERCOM::setClockSource(int8_t idx, SercomClockSource src, bool core) {
   if(core) clockSource = src; // Save SercomClockSource value
 
   // From cores/arduino/startup.c:
-  // GCLK0 = F_CPU (this is 120 MHz and exceeds SERCOM maximum)
+  // GCLK0 = F_CPU (this is 120 MHz and exceeds SERCOM maximum, limit to 100Mhz)
   // GCLK1 = 48 MHz
   // GCLK2 = 100 MHz
   // GCLK3 = XOSC32K

cores/arduino/SERCOM.h

@@ -214,10 +214,10 @@ class SERCOM
 
 		void resetWIRE( void ) ;
 		void enableWIRE( void ) ;
-    void disableWIRE( void );
-    void prepareNackBitWIRE( void ) ;
-    void prepareAckBitWIRE( void ) ;
-    void prepareCommandBitsWire(uint8_t cmd);
+                void disableWIRE( void );
+                void prepareNackBitWIRE( void ) ;
+                void prepareAckBitWIRE( void ) ;
+                void prepareCommandBitsWire(uint8_t cmd);
 		bool startTransmissionWIRE(uint8_t address, SercomWireReadWriteFlag flag) ;
 		bool sendDataMasterWIRE(uint8_t data) ;
 		bool sendDataSlaveWIRE(uint8_t data) ;
@@ -233,12 +233,12 @@ class SERCOM
 		bool isRestartDetectedWIRE( void ) ;
 		bool isAddressMatch( void ) ;
 		bool isMasterReadOperationWIRE( void ) ;
-    bool isRXNackReceivedWIRE( void ) ;
+                bool isRXNackReceivedWIRE( void ) ;
 		int availableWIRE( void ) ;
 		uint8_t readDataWIRE( void ) ;
 		int8_t getSercomIndex(void);
-	uint32_t getSercomFreqRef(void);
-#if defined(__SAMD51__)
+                uint32_t getSercomFreqRef(void);
+#if defined(__SAMD51__) || defined(__SAME51__) || defined(__SAME53__) || defined(__SAME54__)
 		// 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
@@ -254,9 +254,9 @@ class SERCOM
 		uint32_t getFreqRef(void) { return F_CPU; };
 #endif
 
-	private:
-	Sercom *sercom;
-	uint32_t freqRef = 48000000; // Frequency corresponding to clockSource
+          private:
+                Sercom *sercom;
+                uint32_t freqRef = 48000000ul; // Frequency corresponding to clockSource
 #if defined(__SAMD51__) || defined(__SAME51__) || defined(__SAME53__) || defined(__SAME54__)
                 SercomClockSource clockSource;
 #endif