[eqvinox]

At that point it's not a debug connector anymore. Note there's a pseudo-standard for V.24/RS232 on RJ45 already, and nobody uses it for debug connectors since (a) you'd need a RS232 transceiver and (b) RJ45 connectors are honking huge.

The point is to shave off the last cent, which is why you get a possibly-unpopulated 1×4 or 1×3 2.54mm header. Bonus points if the manufacturer designed series resistors into the board (let's say 0402 or even 0201) and left those out too to save the last 0.01 cent.

[pocksuppet]

I think they mean the debug adapter should auto-detect all these things, not the debug port. You'd have one adapter you could plug in to anything and it would usually magically work.

[Aloha]

yes, largely - even if its just pin headers adding a detect line which shows a resistance between it and ground would be an improvement.

In my working life I've seen -

at least 3 different ways to do RS-232 on 8p8c

DTE-DCE is always an issue on standard 232, otherwise I wouldn't have so many null modem cables

232 and 3.3v TTL on the same board or assembly

3.3v and 5v TTL on the same board or assembly

Inconsistent labelling.

I'm in my mid 40's and I think there is a reasonable chance something with RS-232 serial timings will outlast me, it'd be nice to make it more foolproof, as its one of a very few interfaces that will work without drivers.

I do think as a matter of standard good design practice we should be putting clamping diodes on debug ports to prevent blowing things up if hit with the wrong voltage,

[derefr]

> the point is to shave off the last cent

A Tag-Connect footprint has a BOM cost of zero. (Though not a TCO of zero in a closed enterprise ecosystem, as everyone needing to debug the devices needs to buy a stupid $60 pogo-pin cable.)

[Aloha]

I'm open to other options, the biggest things is DTE-DCE auto detection

[eqvinox]

> I'm open to other options,

Err… if you're trying to approach the problem, the onus is on you to come up with options?

I'm not going to preclude you from being creative and coming up with a zero-cost solution that somehow magically does all this, but personally speaking I'd say the chances are minute and it's not worth my time.

I'm also not gonna try to stop you from building that thing you originally suggested, with the 8P8C or 10P10C connector and strapping pins and autodetection and whatnot, I'm just pointing out to you the issues I think it will run into. You're free to ignore my concerns. I'm a random commenter on the internet.

P.S.: calling it DTE-DCE auto detection signals to me that you haven't done a lot of work in this field; those terms are not in common use for TTL serial. People in the field would probably call it something like "TX/RX swap". (Hard to say, since it doesn't really exist.) Maybe you're an engineer for field buses or something like that though…