The developer info says that RTS/CTS isn't implemented in the serial driver.. the serial VFD I'm using is occasionally slow and can't keep up with data being sent, so I need a way to read it's "busy" line and not send any more data until it goes low again. Right now the busy line is connected to the Empeg CTS, which the player uses for display dimming, so I can see it flipping on and off.

How do I check the status of the serial control lines from a userland app?