Thanks! I guess I just was wondering if I could "cheat" = low parts count, using say 2 lines of a PIC output, driving A hi and B low, and A and B are my output lines. Then drive A low and B high, and thus flipping polarity, ....
wait, that's not differential.
I guess I think of traditional signals as being like the on-board - reference to ground, and say TTL being +5 and ground.
I think of differential as the 2 output lines having NO ground reference, and being driven "apart" (say 0v and anything - say 5v). Thus +2.5 -2.5.
I guess I could have TTL differential output by having say one output line is tied to pin A, which is tristated and pulled up/down by 1K's. Thus it puts out 2.5, and when you want, you un-tri-state the pin to say +5, or 0, while the "B" pin, similarly held at 2.5V with a pair of 1K's (not a very strong signal since 1K can be overcome easily) is then pulled to the opposite voltage, producing an opposite - though always positive WRT Ground - voltage. ..
BOY would it be neat to be building a house, and being able to run LV wiring / extra twisted pair signal cables "all over the place", heck, I keep thinking - have for years - you have FIBER/FIBRE running everywhere, if there was an easy way to "insert nodes".
Some of the "highly wired" or "home of the future" seem to put sensors on "everything" like every door, light, etc. Wonder if they hard wire all those? Oh, those are probably rich people and they can afford a wireless chip at every node? It would just have to transmit on state change, then go back to sleep, perhaps waking once an hour to "check in" for a health check, or "my batt is dying", etc.
Thank you all for the wonderful replies. I posted some msgs in other places - simple MOSFET question, and got no answers in 1.5 yrs. ;-)