Add LoRA.setSPIFrequency(frequency) API (#5)

API.md

@@ -32,6 +32,17 @@ LoRa.setPins(ss, reset, dio0);
 
 This call is optional and only needs to be used if you need to change the default pins used.
 
+### Set SPI Frequency
+
+Override the default SPI frequency of 10 MHz used by the library. **Must** be called before `LoRa.begin()`.
+
+```arduino
+LoRa.setSPIFrequency(frequency);
+```
+ * `frequency` - new SPI frequency to use, defaults to `10E6`
+
+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 `LoRa.setSPIFrequency(frequency)`.
+
 ### End
 
 Stop the library

keywords.txt

@@ -46,6 +46,7 @@ noCrc	KEYWORD2
 
 random	KEYWORD2
 setPins	KEYWORD2
+setSPIFrequency	KEYWORD2
 dumpRegisters	KEYWORD2
 
 #######################################

src/LoRa.cpp

@@ -413,6 +413,11 @@ void LoRaClass::setPins(int ss, int reset, int dio0)
   _dio0 = dio0;
 }
 
+void LoRaClass::setSPIFrequency(uint32_t frequency)
+{
+  _spiSettings = SPISettings(frequency, MSBFIRST, SPI_MODE0);
+}
+
 void LoRaClass::dumpRegisters(Stream& out)
 {
   for (int i = 0; i < 128; i++) {

src/LoRa.h

@@ -51,6 +51,7 @@ public:
   byte random();
 
   void setPins(int ss = LORA_DEFAULT_SS_PIN, int reset = LORA_DEFAULT_RESET_PIN, int dio0 = LORA_DEFAULT_DIO0_PIN);
+  void setSPIFrequency(uint32_t frequency);
 
   void dumpRegisters(Stream& out);