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The Serial TTL connector we deserve

kohlschuetter.github.io

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Re: The Serial TTL connector we deserve

#61

Post by foresto »

ycui7 wrote: post #51
foresto wrote: post #8

FTDI (the company practically synonymous with TTL serial adapters) uses 3.5mm tip-ring-sleeve connectors for this. In other words, a common headphone jack. I added one to my single-board computer enclosure, following FTDI's wiring. Now I can easily connect whenever I need to use the serial console, and a standard 3.5mm audio extension cable will let me reach across the room without moving my main computer. Replacemen…

Every vendor defines their audio jack connector serial port differently. It is very dangerous to use 3.5mm jack. There is no pinout standard of using 3.5mm. Even as pure audio jack, the 3.5mm connector has two standards, with the difference on ground and mic.

Well, not every vendor does it differently, because there are far more vendors than possible wiring permutations on a 3-contact connector... but I understand what you mean.

The same issue applies to PCB header pins.

And the same goes for 25-pin D-sub connectors, which have been widely used as RS-232, parallel printer, and SCSI ports.

Voltages vary, too.

This is why we check before wiring them to other things.

Re: The Serial TTL connector we deserve

#62

Post by amelius »

Aurornis wrote: post #28
amelius wrote: post #16

I always wonder why Molex makes only black and white connectors. This makes it needlessly difficult to use different connectors for different purposes. Same with phoenix contact but there it's mostly green terminal blocks. Is it so difficult to just offer some more colors?

They’ll make them in any color you want if you order enough. Adding more colors would multiply their logistic and inventory requirements, which are already hard with so many different connectors multiplied by number of pin options. Multiplying that even further by number of colors that most people would never buy isn’t a win.

I mean, LEGO can make the same brick in many different colors. With much lower tolerances.

Re: The Serial TTL connector we deserve

#63

Post by eqvinox »

foresto wrote: post #59
jaeckel wrote: post #56

Earlier quoted context omitted.

Since I once had the case where junk on the line (from a wiggly connection) caused Magic Sysrq requests I'm fully on your side. No junk tolerated for potential hot plug connections.

What byte sequence on a Tx/Rx/Gnd serial line can trigger Sysrq key sequences?

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.

Re: The Serial TTL connector we deserve

#64

Post by eqvinox »

murderfs wrote: post #60
eqvinox wrote: post #46

Earlier quoted context omitted.

Yes, yes :). I was really joking with the 7 pins. It would be amazing though to make it a hermaphroditic 4 or 6pin connector. With a pinout like this: GND TX [VrefTX VrefRX] RX GND So it always plugs at a 180° rotation, connecting RX to TX. And any cable also rotates 180°. Since you always have an odd total of (connections + cables), you always get the right connection...

Better yet, you could add more pins and switch them to using differential pairs to make it extensible for more use cases. While you're at it, you could have pins on both the top and bottom of the connector, and use a pair of sense pins to detect orientation, so that super specialized use cases can use every single pin available on the connector. GND TX1+ TX1- VBUS CC1 D+ D- SBU1 VBUS RX2- RX2+ GND GND RX1+ RX1- VBUS…

I noted this in https://news.ycombinator.com/item?id=48079649

I also pointed out in that comment that USB-C debug accessory detection does not support orientation detection - and neither does the Google adapter you linked (it doesn't use debug accessory mode, and doesn't have some other solution either). As they say: "Determine correct orientation - top vs. bottom - the tool operates correctly only when SBU1 pin corresponds to TX and SBU2 pin corresponds to RX."

The fact that you can't detect orientation in debug accessory mode is a direct result of how it works: both CC lines are connected to the peer; normally the cable pulls one of the two to ground which is then your orientation reference for all the other pins. (This is also why you can't use a regular USB-C receptacle for debug accessories, it has to be direct to plug, the 2nd CC line doesn't go through the cable.)

So, if you use the SBU pins, it's not reversible anymore. If I remember correctly, debug accessories must still put USB on D+/D-, so the remaining option is to put serial RX/TX on the high speed pins, twice each on 180° positions.

Re: The Serial TTL connector we deserve

#66

Post by kalleboo »

amelius wrote: post #62
Aurornis wrote: post #28

Earlier quoted context omitted.

They’ll make them in any color you want if you order enough. Adding more colors would multiply their logistic and inventory requirements, which are already hard with so many different connectors multiplied by number of pin options. Multiplying that even further by number of colors that most people would never buy isn’t a win.

I mean, LEGO can make the same brick in many different colors. With much lower tolerances.

Have you seen what LEGO costs though?

Re: The Serial TTL connector we deserve

#67

Post by kotaKat »

foresto wrote: post #8

FTDI (the company practically synonymous with TTL serial adapters) uses 3.5mm tip-ring-sleeve connectors for this. In other words, a common headphone jack. I added one to my single-board computer enclosure, following FTDI's wiring. Now I can easily connect whenever I need to use the serial console, and a standard 3.5mm audio extension cable will let me reach across the room without moving my main computer. Replacemen…

Funny - in the retail industry, we use a 1/4" jack instead that runs straight RS232 level traffic (for "DEX" - data exchange - typically sending invoices to a merchant from a route driver, or pulling data from vending machines on a route).

........ and the DEX pinout has Rx/Tx in reverse (our tip receives and our ring transmits) in comparison to the FTDI TTL setup. Wellp!

Re: The Serial TTL connector we deserve

#69

Post by aardvarkdriver »

FWIW, my initial thought here was not transistor-transistor logic but through-the-lens (re: camera light metering). I was excited to learn that maybe someone had waded through the stovepiped mess of TTL metering across camera manufacturers and developed an open-source solution.

Re: The Serial TTL connector we deserve

#70

Post by Aurornis »

amelius wrote: post #62
Aurornis wrote: post #28

Earlier quoted context omitted.

They’ll make them in any color you want if you order enough. Adding more colors would multiply their logistic and inventory requirements, which are already hard with so many different connectors multiplied by number of pin options. Multiplying that even further by number of colors that most people would never buy isn’t a win.

I mean, LEGO can make the same brick in many different colors. With much lower tolerances.

Making them in different colors is the easy part. Inventorying and selling them is the hard part.

LEGO knows exactly the demand for every color of every piece because they make the sets.

If they made 10 different colors of the connector, they’d still sell mostly white and black. Then the rest would sit on shelves and take up manufacturing line time and shelf space. Then they’d have to reprice them to sell off the colors that weren’t moving.

LEGO has none of these problems. Everything goes into a set or retail package they make. The individual loose bricks go into a limited number of options at a few retail stores.

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