needs a few more wires

Im building a egg incubator using a mega 2560 as the controller. The wires have to fit into a space between the door channel and the seal so I can only get 8 wires from the mega to the front panel

im using a 4x20 display on IC2 and 4 buttons (edit/up/down/light) but I want to add another 3 outputs. On hand I have a Attiny85 and I have a extra IC2 lcd interface in the post both I think can be made to be used for the extra outputs.

the input buttons are used in the program in such a way that I don't think I can add them to the IC2 as you have to hold the edit button while using the up and down buttons on certain screens.

If the outputs fail that's not a big deal as long as the mega does not hang waiting for wire transfer (mega is doing temp control and pwm the heater so hanging is a bad thing)

any ideas of what posts/links I should be researching?

im thinking tinywire on the attiny as a slave and wire.h on the mega as master but im worried about data failing to transfer and the loop stopping in the mega.

I'm assuming your Mega is inside the incubator. How many wires would you need if it was outside?

Could you have a second Arduino outside the case. Then the two Arduinos could communicate over 3 wires or using Bluetooth.

...R

Ribbon cable?

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