iCE40: Is it possible with the signal 'ENABLE_OUTPUT' of the primitive SB_IO to create a bi-directional Low Voltage Differential Signaling (LVDS) IO?
No. the signal 'ENABLE_OUTPUT' of the primitive SB_IO (IO primitive of the iCE40) cannot be used to create a bi-directional LVDS IO. One has to use two separate pairs of IOs for LVDS Tx and LVDS Rx.