FL-176 LF RFID RX (#248)

* pulldown ibutton pin during rfid read
* enable and handle COMP interrupts
* send events from comparator IRQ and handle in app
* manchester encode
* successfully read em4100
* read-emulate
* led

firmware/targets/f3/Inc/stm32wbxx_it.h

@@ -56,6 +56,7 @@ void DebugMon_Handler(void);
 void EXTI1_IRQHandler(void);
 void EXTI2_IRQHandler(void);
 void USB_LP_IRQHandler(void);
+void COMP_IRQHandler(void);
 void EXTI9_5_IRQHandler(void);
 void TIM1_TRG_COM_TIM17_IRQHandler(void);
 void TIM2_IRQHandler(void);