[Bug 284042] FTDI: UART breaks JTAG

From: <bugzilla-noreply_at_freebsd.org>
Date: Mon, 13 Jan 2025 23:22:17 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=284042

--- Comment #2 from bsd@orsolic.org ---
I have 2 interfaces after connecting FTDI: /dev/cuaU0 and /dev/cuaU1.

There are no other USB UARTs connected nor UART sessions (cu will exit when
device disappears).

Just running "stty -a -f /dev/cuaU1" (UART) is enough to break JTAG (cuaU0).

What I should do with devd? Making it to link 1st channel to /dev/jtag and 2nd
to /dev/uart doesn't change things (stty -a -f /dev/uart will break JTAG).

HW flow seems to be disabled by default?
stty -a -f /dev/cuaU1 | grep -E 'rts|dtr'
cflags: cread cs8 -parenb -parodd hupcl clocal -cstopb -crtscts -dsrflow
        -dtrflow -mdmbuf rtsdtr

If I kludge uftdi to skip creating interface for 1st channel then only
/dev/cuaU0 will be created (for the UART), but using UART still breaks JTAG.

There is a buffer on JTAG port on my HW
https://docs.espressif.com/projects/esp-dev-kits/en/latest/other/_static/esp-prog/schematics/SCH_ESP32-PROG_V2.1_20190709.pdf
I can try it without buffer when I got my custom PCB which doesn't have buffer.

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