Hi,
Im making a custom board and I have a 5V serial port on this board which is used to connect other devices with 5V serial. The Vcc pin is an output for my board. My concern is what happens if the other devices that i connect to also has their Vcc pin as an output. Will they just cancel out or will this potentially damage my board, or the other device, especially if there are fluctuations on either of the 5V lines. i'm using mega2560 as the mcu by the way, not sure if this is important.
I'm thinking of putting a diode there to ensure 1 way flow of current, is this a good idea?
Post a schematic so we can have a clearer idea of what you want to do. Hand drawn, photographed and posted is fine.
It is very seldom a good idea to connect outputs together. Especially power suppy positive outputs (Vcc). They can fight each other and cause nasty problems.
Grounds are different. Usually all the grounds need to be connected together.
If you are connecting severql boards serial outputs together that is a NoNo. If you want to do something like that you need to use an interfaced to allow multiple users transmit and receive. A very popular one is CAN especially if it is mainly control data and reliability is important.
No, i'm not connecting multiple serial devices at the same time.
i use this port as some sort of general purpose serial port..
i connect my laptop through this port for diagnostics purposes, or sometimes an arduino for simulation purposes.
This is probably not what you mean, but it is as close as I can figure. Showing 2 Unos connected by a serial port. Each Uno has its own 5V supply (Vcc), but the grounds are shared so the signals (TX, RX) have a reference.
DC Power sources, usb, batteries, etc. have two wires: GND (ground, or 0V) and positive, also known as VCC, V+ and other names. VCC can be 3.3V for some of your devices, 5V for others, and 12V or whatever for still other devices in the same circuit.
In a typical setup you connect all grounds together, but you never connect VCC from one source to another, even if they are all 5V, for example.
Your chances of getting help here will be much higher if you post a connection diagram or schematic showing what you want to do.
