I’m new to Fritzing and PCB design, and I’m wondering if Fritzing is useful for designing a board that’s not a complete circuit? I’m planning to make a board with an i2c I/O extender chip and some switches. My plan is to use a 4-wire cable to connect it to a Teensy that’s not on the board. How would you model this?
Welcome aboard, yes Fritzing will do this. You just drag in the I/O extender chip, the switches and a 4 pin generic header in to a sketch, connect the parts in breadboard or schematic then complete the routing in pcb view (the connections will appear there from breadboard or schematic.) The connection to the Teensy occurs via the 4 pin generic header on the board. Have a look at this project (you need to download the .fzz file and load that in to Fritzing) as a poor example. Schematic is complete but breadboard and pcb are not but it gives the idea.
The mcp23017 chip is available as a Fritzing part in the forums here:
assuming that is what you want to use as the io expander.
Thanks! Since I would only have part of a circuit, is there any kind of circuit simulation that I would be missing out on? In software terms, I’m a bit unclear on when I’m just drawing pretty pictures for human communication (like comments or documentation), versus writing code that actually does something, either in simulation or when ordering the board to be made.
No. Fritzing doesn’t generally have simulation (if the spice data is in parts it can be used with an external spice program, but not many parts have spice data.) You are mostly producing documentation (breadboard and schematic) which is sometimes the end result. For a pcb the end result is usually the gerber files which describe the board to the board house that makes the boards. In this case you should probably start from breadboard and breadboard and test the circuit on a real breadboard to make sure it works, then produce schematic (if you want one) and pcb to make the actual boards. With breadboard completed correctly Fritzing will provide rats nest lines in schematic and pcb to create the interconnections. It is best practice to complete the entire circuit in one view (breadboard in this case) then do the other two as mistakes in one view will propagate to the other two views and may cause problems. Feel free to ask for help here as the documentation is usually lacking.