Try it. It works quite well. It’s not that the driver hangs, it is that the driver won’t accept serial input until the DTR requirement is satisfied. So, you simply set the handshake characteristics for the port, and the driver will immediately start accepting data.
Think back on what the requirements were - when the DTR state changed, the port would grab the Getty’s attention, establishing a new user session. This was back in the days of very minimal hardware capabilities. In fact many of the systems did not have hardware UARTs. The driver was active even if not opened so that it could do its task. These days the drivers for cu and tty are the same, and are not actually opened until the application opens them. I haven’t seen a system with serial TTYs active for years - we do that using networking these days. Again, it really doesn’t matter which port of the pair you call out in the application, just set it up properly and use it. That means setting it up completely, including blocking characteristics and handshaking. And, if you want it to work well, use GCD blocks to handle the reads so that you spend minimal time in the handler code. That definitely gives cool to the system. > On Jun 8, 2015, at 6:17 PM, Carl Hoefs <[email protected]> wrote: > > >> On Jun 8, 2015, at 6:13 PM, Jack Brindle <[email protected] >> <mailto:[email protected]>> wrote: >> >> You set the port environment immediately after you open it > > A tty device hangs on open until DTR is asserted, so how can you open it to > change it if it blocks? > -Carl >
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