2017-06-17 18:34 GMT+03:00 Danny Miller: > That's not a true differential output. It's an optoisolator's two output > terminals. Since they're isolated, neither terminal is tied to a gnd or + > so you can connect it high or low. > > When tripped, it conducts current (supplied externally) from + to -. It > cannot generate its own voltage, only conduct. >
> So all you need to do is hook it to a pin with an external pullup. AFAIK > all the 7i47 have a pullup to +5v. Alarm+ to pin, Alarm- to gnd. The > pin will go low when the Alarm signal is active. > > Similarly the inputs aren't true differential, they're an optoisolator's > input diode with a series resistor to produce the rated trigger current > when +5v is applied + to -. Due to some esoteric details in how the bus > switch drive output works, these work best if you tie the + to +5v and use the pin to drive the - to gnd. The signal is weaker if you do it > the other way. Thanks for the tip! I was going to try the weaker way. If there's a series resistor, it's safe to drive full 5V between /RX and RX. 7i47s has GND and 5V pins near RX terminals, pretty handy to connect either way. Thanks, Andrew ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
