It was not THAT huge issue, I tried both pull up and down with a 10K resistor, but got different reaction upon connecting of different usb-serial, that's why i asked for better options. Currently it's left with pull-up, which seemed more logical. On 15 April 2014 15:00, Bob Ammerman wrote: > It seems a little surprising that this is such a big issue. A reasonable > value resistor to +5 or ground (depending on which is the correct idle st= ate > for serial TTL, I forget) should do the job just fine. I would suggest > something like 10K, which almost any reasonable signal source can overrid= e. > Assuming a 5V supply you would have need 0.5 ma of current draw to pull i= t > to the opposite rail. > > -- Bob Ammerman > RAm Systems > > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf = Of > KPL > Sent: Tuesday, April 15, 2014 3:01 AM > To: Microcontroller discussion list - Public. > Subject: Re: [EE] noise-proofing open serial interface lines > > Seems like my english and description skills have failed, as usually. > > That interface is left there just for very rare occasions when some > reconfiguration is needed, like RTC adjustments or irrigation reschedulin= g. > All the other time there will be absolutely nothing connected, and i just > want make sure those lines will not pick up a lot of noise at that time, = as > that will cause controller to try to parse what it has received. No long > wires, just a short cable to a connector in the same housing. > Even if lantronix will be permanently connected there for some reason, it > will be located in the same box, as ethernet will be used for remote acce= ss. > > On 12 April 2014 11:46, William "Chops" Westfield wrote: >> On Apr 7, 2014, at 2:05 PM, Jesse Lackey wrote: >> >>> If possible, you could use RS-485 instead of TTL-level. >> >> Real rs232 would be better than TTL, too. Aside from the wider >> voltage margins, I think real rs232 has somewhat controlled impedance. >> And most modern converter chips will include some ESD protection as well= .. >> >> BillW >> >> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > KPL > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/cha= nge > your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 KPL --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .