[ntp:questions] WinXP no DCD interupts unless RTS/CTS handshaking enabled

James Gibb jamesgibb at clannet.co.uk
Thu Apr 10 08:49:08 UTC 2014

I'm not sure if this is a generic problem or something weird has happened to the UARTs on my box, but I find I only see DCD events if RTS/CTS handshaking is on.  This is true for David Taylor's SerialPort LEDs viewer, RealTerm (a Windows terminal/debugging program) and NTPd.  I've hacked refclock_open to set the DCB flags fOutxCtsFlow to 1 and fRtsControl to RTS_CONTROL_HANDSHAKE and it sees PPS; otherwise it does not.

Now, last week it was seeing the PPS without those hacks.  Since then I've disconnected an oscilloscope and re-worked the wiring around a level converter which temporarily broke PPS at the wire level.  I can't remember using anything except the LED viewer and RealTerm to check I'd got it working again and I had used both prior to that and they didn't cause this interrupt disabling.

Anyone any ideas what's happened?

// James Gibb

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