I'm doing a serial line between a main board with a 1284P at 5V and another board with an ESP8266 at 3.3V. So I gotta use a level shifter. No problem, I got one and I know how to use it. It all goes over a 4 (22 or 24ga i can't remember and can't tell) wire cable (rx, tx, gnd, ?power maybe?) over a length of about 30 or 40 cm. I already have both 5V and 3.3V on both boards. My question is, should I put the level shifter on the main board where I have lots of real estate, or should I put it on the board with the ESP where I can just squeeze it in. Or I guess to put it another way, is there any advantage to keeping the higher voltage in the wire and waiting until the end to shift it down? Or is it all the same putting 5V or 3.3V serial over a wire like that.
The ideal situation is: let the high voltage travel the wire, shift at the receiver side.
(Which might be more complicated than your proposed solutions.)
Of course, there is a lot of "it depends" in here, depending on wire length.
cmiyc:
The ideal situation is: let the high voltage travel the wire, shift at the receiver side.(Which might be more complicated than your proposed solutions.)
Of course, there is a lot of "it depends" in here, depending on wire length.
Gotcha. It's six of one and half a dozen of the other from the design standpoint. But the only thing leaning it towards the main board was laziness and I can't let that be the deciding factor if there's anything else out there.
Though it is not best practice, all the ESP-01 modules I have work without the level shifter.