Electronic switches like the 4066 would work. But individual FETs would work well too. Regards, Jim > -------- Original Message -------- > Subject: [EE] Circuit to allow product with RS232, RS485, and RS422 on > same pins? > From: Jason White > Date: Wed, March 13, 2019 10:53 am > To: "Microcontroller discussion list - Public." >=20 >=20 > Hello everyone, >=20 > My work has a product that has four pins for RS232, RS485, or RS422. > Previously the product was built as either RS232 or RS485/RS422 - only > containing a transceiver for one or the other but not both. But now we > want to make a product that can be electronically configured as one or > the other. The problem is that the same pins are used for each > interface! >=20 > I was wondering if anybody has any suggestions for a circuit that > would permit the either of the transceivers (232 and 422) to be > disconnected from the circuit - so that only one was physically > connected to the pins at a time. Off the top of my head I can think of > two solutions: >=20 > (1) Signal relays on the input/output of each transceiver. This would > permit the 232/422/485 to be on the same pins. > Pros: Robust > Cons: bulky, power hungry, and expensive. >=20 > (2) Electronic switch, would a CD4066B work? An electronic switch is > desirable but many don't handle the voltages required. For instance > the MAX232 tolerates +/-30V whereas the seemingly obsolete CD4066B > only handles 0-15V, requiring protection. > Pros: Smaller > Cons: Not sure how to implement, inadequate voltage tolerance >=20 > --=20 > Jason White > --=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 --=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 .