attempt to emphasise pin numbering

src/en/overlay/i2c.md

@@ -24,9 +24,10 @@ pin:
     active: high
 -->
 #I2C - Inter Integrated Circuit
-
+---
+###I2C pins in BCM mode are: 2, 3
 ###I2C pins in WiringPi are: 8, 9
-
+---
 The Raspberry Pi's I2C pins are an extremely useful way to talk to many different types of external peripheral; from the MCP23017 digital IO expander, to a connected ATmega.
 
 The I2C pins include a fixed 1.8 kohms pull-up resistor to 3.3v. This means they are not suitable for use as general purpose IO where a pull-up is not required.

src/en/overlay/spi.md

@@ -46,9 +46,10 @@ pin:
     name: SPI1 SCLK
 -->
 #SPI - Serial Peripheral Interface
-
+---
+###SPI0 pins in BCM mode are: 9, 10, 11 + 7/8
 ###SPI0 pins in WiringPi are: 12, 13, 14 + 10/11
-
+---
 Known as the four-wire serial bus, SPI lets you daisy-chain multiple compatible devices off a single set of pins by assigning them different chip-select pins.
 
 A useful example of an SPI peripheral is the MCP23S17 digital IO expander chip ( Note the S in place of the 0 found on the I2C version ). You can also use the SPI port to "Bit-Bang" an ATmega 328, loading Arduino sketches onto it with Gordon Hendersons' modified version of AVRDude.

src/en/overlay/uart.md

@@ -17,9 +17,10 @@ pin:
     active: high
 -->
 #UART - Universal Asynchronous Receiver/Transmitter
-
+---
+###UART pins in BCM mode are: 14, 15
 ###UART pins in WiringPi are: 15, 16
-
+---
 UART is an asynchronous serial communication protocol, meaning that it takes bytes of data and transmits the individual bits in a sequential fashion.
 
 Asynchronous transmission allows data to be transmitted without the sender having to send a clock signal to the receiver. Instead, the sender and receiver agree on timing parameters in advance and special bits called 'start bits' are added to each word and used to synchronize the sending and receiving units.