Remove clockRate arg from begin, add new setClockFrequency API

Author: sandeepmistry

API.md

@@ -14,10 +14,8 @@ Initialize the library with the specified bit rate.
 
 ```arduino
 CAN.begin(bitrate);
-CAN.begin(bitrate, clockRate);
 ```
  * `bitrate` - bit rate in bits per seconds (bps) (`1000E3`, `500E3`, `250E3`, `200E3`, `125E3`, `100E3`, `80E3`, `50E3`, `40E3`, `20E3`, `10E3`, `5E3`)
- * `clockRate` - (optional) clock rate of clock source (`8E6`, `16E6`, `20E6`) connected to MCP2515, defaults to `16 Mhz`
 
 Returns `1` on success, `0` on failure.
 
@@ -44,6 +42,17 @@ CAN.setSPIFrequency(frequency);
 
 This call is optional and only needs to be used if you need to change the default SPI frequency used. Some logic level converters cannot support high speeds such as 10 MHz, so a lower SPI frequency can be selected with `CAN.setSPIFrequency(frequency)`.
 
+### Set Clock Frequency
+
+Override the default clock source frequency that is connected to the MCP2515. **Must** be called before `CAN.begin(...)`.
+
+```arduino
+CAN.setClockFrequency(clockFrequency);
+```
+ * `clockFrequency` - new clock frequency to use (`8E6`, `16E6`) connected to MCP2515, defaults to `16 Mhz`
+
+This call is optional and only needs to be used if you need to change the clock source frequency connected to the MCP2515. Most shields have a 16 MHz clock source on board, some breakout boards have a 8 MHz source.
+
 ### End
 
 Stop the library

keywords.txt

@@ -39,6 +39,7 @@ wakeup	KEYWORD2
 
 setPins	KEYWORD2
 setSPIFrequency	KEYWORD2
+setClockFrequency	KEYWORD2
 dumpRegisters	KEYWORD2
 
 #######################################

src/CAN.cpp

@@ -50,6 +50,7 @@ CANClass::CANClass() :
   _spiSettings(10E6, MSBFIRST, SPI_MODE0),
   _ss(CAN_DEFAULT_SS_PIN),
   _irq(CAN_DEFAULT_INT_PIN),
+  _clockFrequency(CAN_DEFAULT_CLOCK_FREQUENCY),
   _onReceive(NULL),
 
   _packetBegun(false),
@@ -70,7 +71,7 @@ CANClass::CANClass() :
   setTimeout(0);
 }
 
-int CANClass::begin(long baudRate, long clockRate)
+int CANClass::begin(long baudRate)
 {
   _packetBegun = false;
   _txId = -1;
@@ -98,7 +99,7 @@ int CANClass::begin(long baudRate, long clockRate)
   }
 
   const struct {
-    long clockRate;
+    long clockFrequency;
     long baudRate;
     uint8_t cnf[3];
   } CNF_MAPPER[] = {
@@ -132,7 +133,7 @@ int CANClass::begin(long baudRate, long clockRate)
   const uint8_t* cnf = NULL;
 
   for (unsigned int i = 0; i < (sizeof(CNF_MAPPER) / sizeof(CNF_MAPPER[0])); i++) {
-    if (CNF_MAPPER[i].clockRate == clockRate && CNF_MAPPER[i].baudRate == baudRate) {
+    if (CNF_MAPPER[i].clockFrequency == _clockFrequency && CNF_MAPPER[i].baudRate == baudRate) {
       cnf = CNF_MAPPER[i].cnf;
       break;
     }
@@ -434,6 +435,11 @@ void CANClass::setSPIFrequency(uint32_t frequency)
   _spiSettings = SPISettings(frequency, MSBFIRST, SPI_MODE0);
 }
 
+void CANClass::setClockFrequency(long clockFrequency)
+{
+  _clockFrequency = clockFrequency;
+}
+
 void CANClass::dumpRegisters(Stream& out)
 {
   for (int i = 0; i < 128; i++) {

src/CAN.h

@@ -7,16 +7,16 @@
 #include <Arduino.h>
 #include <SPI.h>
 
-#define CAN_DEFAULT_CLOCK_RATE 16e6
-#define CAN_DEFAULT_SS_PIN     10
-#define CAN_DEFAULT_INT_PIN    2
+#define CAN_DEFAULT_CLOCK_FREQUENCY 16e6
+#define CAN_DEFAULT_SS_PIN          10
+#define CAN_DEFAULT_INT_PIN         2
 
 class CANClass : public Stream {
 
 public:
   CANClass();
 
-  int begin(long baudRate, long clockRate = CAN_DEFAULT_CLOCK_RATE);
+  int begin(long baudRate);
   void end();
 
   int beginPacket(int id, int dlc = -1, bool rtr = false);
@@ -47,6 +47,7 @@ class CANClass : public Stream {
 
   void setPins(int ss = CAN_DEFAULT_SS_PIN, int irq = CAN_DEFAULT_INT_PIN);
   void setSPIFrequency(uint32_t frequency);
+  void setClockFrequency(long clockFrequency);
 
   void dumpRegisters(Stream& out);
 
@@ -65,6 +66,7 @@ class CANClass : public Stream {
   SPISettings _spiSettings;
   int _ss;
   int _irq;
+  long _clockFrequency;
   void (*_onReceive)(int);
 
   bool _packetBegun;