In the past, I did have some luck with Mouser TL016 transformers in a multi= -drop scenario. You would have to keep clocking and vary width to send data, or otherwise h= andle the fact that it doesn't do DC. That was probably 1990 or so and I don't remember much else from that exper= iment.=20 The wire was twisted pair, and every node coupled to the wire through a tra= nsformer. Possibly a comparator for receive? I don't remember. -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of= Neil Sent: Wednesday, May 17, 2017 1:08 PM To: Microcontroller discussion list - Public. Subject: [EE] Low-cost differential signaling I'm doing one-way digital communications between 2 PICs about 12 feet apart= .. ~50 kHz max. Cable currently has 12V, ground, and one data wire (5V di= rect from a PIC 18F output). Nothing is twisted yet -- just straight wires= .. At this stage, it's functional and works fine as it is, but I'd like to = add EMI/noise immunity (against possible external noise from other nearby s= ignals). Shielding is noticeably increasing that cabling cost, so I'm thin= king of differential signaling instead. =20 Looking for a simple way to do this. First thought was to use RS-485 or similar differential transceivers, but t= hat adds a few dollars, which is higher than I'd like. CAN transceivers ar= e lower cost (~$0.40 each side). However, CAN is a relatively low-level si= gnal, so I'm thinking that I can just use 2 I/O pins on the sender to creat= e my own differential 5V-ish signal, and use the comparator on the receivin= g PIC to process the differential signal. =20 I would need to add some resistors at the receiving end as the (PIC32) comp= arator inputs can only handle up to 3.3V on that side. From anyone's exper= ience, would this even make a dent in the system's ability to reduce noise = effects? Additionally, I am hoping to have the sender be open-drain, and p= ull-up at the receiver. Should this be hard-driven to 5V instead for bette= r noise immunity? Another thought is that I have 12V available at the sender, so I can use th= at for the signaling level, but that adds a couple transistors. Or I can s= tay open-drain at the sender and pull up to 12V at the receiver, then volta= ge divide. Would it make a difference for differential signaling? Thanks, -Neil. -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=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 .