Nano, Prevent reset on usb serial open

I'm using a Nano as the master controller for a digital organ. When powered up, it triggers a relay that boots up a PC. The PC then opens serial ports to the Nano (and other Nanos). However, the opening of the Serial link triggers a reset which I don't want to happen. How can I prevent this reset from occurring. I understand that this reset is meant to facilitate downloading new code, but I can work around that. Any ideas, please?

What do you use to open the serial port on the PC? A dedicated application? The serial monitor in the IDE? A 3rd party terminal program?

Most terminal programs give the option to suppress the reset when opening the serial port.

If it's a dedicated application, how much control do you have over it? If you wrote it, in which language?

You can also use a number of serial-to-usb adapters and use those to connect your Nanos to the PC instead of the normal USB. That will solve the issue as well.

Or you can cut a trace on the Nano; this will block further uploads but you can find ways around that (upload via ICSP or soldering the trace back).

Thanks! I'm programming in C on LInux (Debian). Further googling suggests that adding HUPCL
to the termios cflags list might do the trick. Can't try this until tomorrow afternoon, but it sounds promising.

Is your nano legit or a clone?

A radical solution that requires skills in working with electronic components
is remove capacitor C4 (official nano) and connect 2 wires in its place.
This 2 wires go to a switch.
In this switch you connect a 100 nF capacitor and a wire, the other wire on the other side of the capacitor, so you can or cannot allow DRT to be reseated in your nano.

In the Arduino clone it appears that the capacitor is C3.
But just locate the capacitor that has one side connected to the reset pin of the atmega328.

I've come up with an alternative solution. I have a small FTDI adapter: USB in one end,
TX,RX and DTR at the other end. Wire it to the TX and RX pins on the Nano and it should do the trick.

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