...
    raise YosysError(stderr.strip())
nmigen._toolchain.yosys.YosysError: ERROR: Multiple edge sensitive events found for this signal!

class BasicFSMDevice(Elaboratable):
    def __init__(self):
        self.clk = Signal()
        self.csn = Signal()
        
    def elaborate(self, platform : Platform):
        m = Module()
        
        m.domains += ClockDomain("asyncFSM", async_reset=True, local=True)
        
        m.d.comb += ClockSignal('asyncFSM').eq(self.clk)
        m.d.comb += ResetSignal('asyncFSM').eq(self.csn)
        
        with m.FSM(domain='asyncFSM', reset='IDLE', name='serialFSM'):
            with m.State('IDLE'):
                m.next = 'BUSY'
            with m.State('BUSY'):
                m.next = 'BUSY'
        
        return m
        
    def ports(self) -> List[Signal]:
        return [
            self.clk,
            self.csn
        ]

if __name__ == "__main__":
    simulate = False

    parser = main_parser()
    args = parser.parse_args()

    m = Module()
    m.submodules.basicFSM = basicFSM = BasicFSMDevice()
    
    main_runner(parser, args, m, ports=basicFSM.ports())