Hi,
I'm trying to solve a problem which I've posted in other threads. The solution I was thinking of would mean using two arduinos each reading and writing to an SD card. From what I've read this doesn't seem possible. I want both arduinos to read the same data to maintain state. This is for a door lock so the state would be "locked" and "unlocked".
Is this possible to do?
DN 
Even if it were possible, my experience with the relaibility of SD cards on Arduinos would prevent me using them for an application such as a door lock, which you would want to be reliable.
it looks like you want to use way more hardware than really need for the project.
I am sure one Arduino can do it (and without the SD card)
Yeah that what I was hoping too, I just can't get my code to work, so annoying.
Which Arduino? The Pro Mini has some EEPROM on chip. You could use that.
If only needed to store "locked" or "Unlocked" you could easily add some parity bits so if the EEPROM location becomes "used up" you can just move to the next address.
@JohnRob I'm using the Mega. I have a switch and RFID and I want them both to be able to check the state of the lock. I can get both working individually but when I try to run them both it doesn't work. That's why I was thinking of using 2 Arduinos. There's other threads where I've posted the code. Not sure what the solution is at the moment.
You can start by providing the sketch that does not want to work and an explanation what it is supposed to do and what it actually does.
@sterretje Here's a thread that explains it further.
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