Hi,
I want to use dip switches to activate/deactivate controller boards Vin and of course they share the same ground line.
Is that safe if the boards; for example, share other signal lines for SPI, I2C or any other pins lines ?
you can have multiple devices on I2C and SPI (each SPI device requires a seperate CS chip select line)
how often would you change the DIP switches - you may find they have a limited lifetime?
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Unfortunately that's not possible. Phantom power will be injected into all connected pins of a chip with power cut off. Only dedicated input pins can be secured by current limiting resistors (1k), not output or bidirectional bus pins.
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I mean, the dip switches, in case I want to work with one controller board and disable the other boards.
My question, if I'm activating one controller board and cutting power of the other two boards, would there a problem to the disabled boards ?
as I'm thinking even if the other two boards are not powered by Vin, they still share the ground line. Could the shared IO lines short the pins of the disabled boards ?
All I/O pins have parasitic or protective diodes to Vcc and GND. These diodes can cause current flowing into the Vcc plane of the entire chip. Same for the GND plane.
With unidirectional lines (SPI....) optocouplers may help to isolate the chips from each other. I don't know of a solution for bidirectional I2C lines.
This is another drawing in a simple form:
If the controller board is not powered from the main voltage source, and there is an active signal on pin 11, could pin 11 shorted or maybe burn internal circuitry ?
Yes. Both controllers may be damaged.
I thought of a solution which is to only plug in the board I want to work with and remove the controllers, how about this solution ?
I'm not interested in communicating with another control board on the same development board for this safety issue.
If I want to communicate with another controller, I would put the other controller on a breadboard or another development board.
Have a connector with all wires to plug the module in and out (JST...). If you only make the controllers communicate over I2C or SPI bus then there are not many pins to disconnect. Kind of a mini bus system including power rails.
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How ? Can you post an image or something to understand more ?
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