Update README.md

README.md

@@ -88,4 +88,15 @@ reset
 shutdown
 ```
 
+## Hello worlds
+
+* <a href='modules/spi'>SPI (Serial Peripheral Interface)</a>
+
+* <a href='modules/twi'>TWI (i.e., I2C)</a>
+
+* <a href='modules/uarte'>UARTE (i.e., UART with DMA)</a>
+
+* <a href='modules/pwm'>PWM (Pulse width modulation)</a>
+
+