UART.irq(trigger, priority=1, handler=None, wake=machine.IDLE)
Create a callback to be triggered when data is received on the UART.
trigger can only be UART.RX_ANY
priority l*l of the interrupt. Can take values in the range 1-7. Higher values represent higher priorities.
handler an optional function to be called when new characters arrive.
wake can only be machine.IDLE.