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eqvinoxtoday at 10:10 AM1 replyview on HN

It's not a byte sequence, it's a BREAK == pulling the line low for longer than a byte, i.e. invalid serial framing on the stop bit.


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forestotoday at 5:33 PM

I'm aware of serial breaks, but this is the first I've heard of them being interpreted as SysRq by Linux. That could be handy. Thanks for the tip.

I assume the possibility of spurious Rx state is why FTDI chose to wire Rx to the tip pin of the female TRS connector: It's the last pin to make contact with anything when plugging in, and therefore least likely to be bridged to ground. I suppose the mechanical design of any particular jack would determine whether it's possible at all.