A IRQ is lost when conflicting with another one

[xiansnn]

The DCF code uses two IRQ :

• one linked to internal timer. Used to step one second local clock change
• one linked to DCF radio signal decoder. Used to process bit sequence received on the radio channel When the DCF related IRQ goes wrong (e.g. when a lot of parasitic signals are received on IRQ gpio pin) it happens that the internal timer IRQ is canceled. Modification on the push button driver debounce algorithm improved the robustness but error still occurs. -- Channel 1 (yellow ) : the audio signal converted in signal envelope that triggs an IRQ on both rising and falling edge. -- Channel 2 (blue ) : the local timer IRQ handler.

[xiansnn]

this commit has removed the issue. It is a simple workaround, not really a solution.

[xiansnn]

The last version DCF77_TextUI v2.py with IRQ based local timer seems more robust,