I opened a small router and hooked up 2 wires on the PCB (to catch the serial data). That works fine.

Now I'm looking for a way to make a small (tiny) connector in the enclosure, so for future use i can easy attach a connector.

My question, in the land of of a billion connectors, what would be a good small (female) connector, panel mount, max. 5x5 mm?

Many thanks.

  • \$\begingroup\$ What signals are you looking at, what are the frequencies and voltage levels? What tolerances (rise/fall time, max latency, voltage level) does the serial protocol require? there are many choices precisely because there are many different signal types. \$\endgroup\$
    – crasic
    Aug 8 '13 at 7:26
  • \$\begingroup\$ Its a simple tx/rx signal. I hooked-it up with a CP2102 (USB ttl/adapter). Its basically 2 wires, i was thinking abusing a small mono jack (2.5mm), but maybe there is something better. \$\endgroup\$
    – Roger
    Aug 8 '13 at 7:35
  • \$\begingroup\$ Was it balanced data you hooked-up to? \$\endgroup\$
    – Andy aka
    Aug 8 '13 at 7:36
  • \$\begingroup\$ Balanced data? Eeks, sorry im a noob :x \$\endgroup\$
    – Roger
    Aug 8 '13 at 7:38
  • \$\begingroup\$ @Rogier, it'll be unbalanced TTL level so you'll need a ground as well. A 2.5mm stereo jack might be OK but one issue is that various pins can short as you plug it in which probably isn't good in this case. \$\endgroup\$
    – PeterJ
    Aug 8 '13 at 7:47

The CP2102 USB to UART Bridge has an unbalanced 3.3V interface so you should be connecting ground in addition to the TX and RX lines. Using a shielded cable probably isn't a bad idea although at fairly standard low baud rates such as 9600, 57600 etc noise immunity is fairly good so you may not have to worry a lot unless the application is critical or you're in an electrically noisy environment. For test purposes I've run 3.3V TTL serial lines over a few meters of unshielded cable without problems.

A connector I've used in the past that is quite robust and offers panel mount in a small form factor is the Binder 709/719 series. The 3-way panel mount part number can be found at Element 14: Binder 09 9750 30 03. They are a little larger than your specifications and not exactly dirt cheap but are very easy to solder to, here's an indicative photo that shows the 4-pin variety:

enter image description here

Your idea of using a 2.5mm audio jack is probably also worth considering although you need to be aware that while inserting the plug some pins can be temporarily shorted. The RX line being shorted to ground or TX won't matter but you should take care with the TX line at each end. Without specific details of the hardware at each end it's hard to know for sure but a 3k3 resistor in series with the TX line at each end will limit the current to 1mA which should be safe for most devices I can think of.

  • \$\begingroup\$ +1 - That looks good, 6.4mm is pretty close. Bit like a tiny XLR plug, will keep that in mind myself for future projects.. \$\endgroup\$
    – Oli Glaser
    Aug 8 '13 at 10:26
  • \$\begingroup\$ @peterj that looks nice! It would fit i think. However the price is a bit steep (2 connectors $20USD), thats more then the device itself. Its nothing critical (its for serial access into the switch, incase you brick the firmware), but your comment on shorten wires when inserting.... ouch! Thanks. \$\endgroup\$
    – Roger
    Aug 8 '13 at 10:34
  • \$\begingroup\$ @Rogier, they seem to have shot up in price although they were pretty dear when I bought them. I'd probably go with option B above, use the 2.5mm stereo jack and a few resistors on the TX line for a bit of extra safety if they get shorted. Static on the RX line could also be an issue, but if a cheap device I probably wouldn't worry much. \$\endgroup\$
    – PeterJ
    Aug 8 '13 at 10:40

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