How are use converting the RS232 output of the USB-Serial adapter to TTL? O= r are you using something like an FTDI with TTL output? I though 0.5ma wouldn't be much of an issue, but you might want to try a higher resistance.=20 -- 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 8:51 AM To: Microcontroller discussion list - Public. Subject: Re: [EE] noise-proofing open serial interface lines 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=20 > reasonable value resistor to +5 or ground (depending on which is the=20 > correct idle state for serial TTL, I forget) should do the job just=20 > fine. I would suggest something like 10K, which almost any reasonable signal source can override. > Assuming a 5V supply you would have need 0.5 ma of current draw to=20 > pull it to the opposite rail. > > -- Bob Ammerman > RAm Systems > > > -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On=20 > 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=20 > reconfiguration is needed, like RTC adjustments or irrigation rescheduling. > All the other time there will be absolutely nothing connected, and i=20 > just want make sure those lines will not pick up a lot of noise at=20 > that time, as that will cause controller to try to parse what it has=20 > 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,=20 > it will be located in the same box, as ethernet will be used for remote access. > > 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=20 >> 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=20 >> View/change your membership options at=20 >> http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > KPL > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 > View/change your membership options at=20 > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 > View/change your membership options at=20 > http://mailman.mit.edu/mailman/listinfo/piclist -- KPL -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=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 .