Updated Basics (markdown)

Basics.md

@@ -1,7 +1,7 @@
 The purpose if this page is to provide an overview of the basic usage of the library API. **For details on each supported radio module, please refer to the provided [examples](https://github.com/jgromes/RadioLib/tree/master/examples).**
 
 ## Standalone Module
-1. Connect the wireless module to the Arduino. This includes connecting the SPI bus, as well as some GPIO pins. The extra pins are used for SPI chips select, hardware reset and GPIO or interrupts. Each module uses slightly different setup. For example, some modules might only have one interrupt pin, while others may have multiple. Some modules might have reset pin, others might do without one.
+1. Connect the wireless module to the Arduino. This includes connecting the SPI bus, as well as some GPIO pins. The extra pins are used for SPI chip select, hardware reset and GPIO or interrupts. Each module uses slightly different setup. For example, some modules might only have one interrupt pin, while others may have multiple. Some modules might have reset pin, others might do without one.
   
 2. Provide the pin setup to the library. This is done using the `Module` constructor in the following format: `Module(cs, irq, rst, gpio)`. For example: `RF69 rf = new Module(10, 2, 3);`
     - CS: this is the pin that's used as SPI chip select.
@@ -22,3 +22,21 @@ The purpose if this page is to provide an overview of the basic usage of the lib
 3. After the object is created, the module has to be initialized using the `begin()` method. Typically, this is done in Arduino `setup()` function. If you want to change the module settings, this can be done by providing appropriate values to the `begin()` method.
   
 4. At this point, your module is ready to send or receive any data you want!
+
+## Non-standard SPI setup
+
+Some platforms (such as ESP32) allow user to change the SPI bus pins. By default, RadioLib is using the `SPI` instance provided by Arduino, and will automatically initialize the bus - usually by calling `SPI.begin()`. However, user may want to use a different SPI bus than the default, or do the initialization outside the library. For this cases, an extended `Module` class constructor is provided, in the format `Module(cs, irq, rst, gpio, &spi, spiSettings)`, where `spi` is a reference to an instance of `SPIClass`, and `spiSettings` is an instance of class `SPISettings`. In such case, RadioLib will not perform any internal initialization of the bus, and therefore this is left up to the user, as shown in an example for SX1278 and ESP32 below.
+
+```c++
+SPIClass spi(VSPI);
+SPISettings spiSettings(2000000, MSBFIRST, SPI_MODE0);
+SX1278 radio = new Module(cs, irq, rst, gpio, spi, spiSettings);
+
+void setup() {
+  spi.begin();
+  (...)
+  radio.begin();
+}
+```
+
+Please not that SPI bus MUST be initialized prior to calling the `begin()` method!