Master Slave Communication between two Arduino Nano and some I2C devices

Hello guys,

I'm searching desperatly for a way or some code examples to establish a datalink between two Arduino Nano. My problem is the following. I'm bulding a alarm clock which should be programed via bluetooth. Since the I/O Pins of one Arduino Nano are not enough why not let the one do the display (9 TM 1637 SevenSegment displays) and the other one the data recieving (HC-05) and RTC (DS3231). I already connected the Pins A4 and A5 from both and the RTC DS3231 Module and used 50k Pull-Up resistors, so the physical connction is established. The circuit plan which I followed is attatched. Since I'm new to the topic of I2C communication I didn't find lots of information how to get the bluetooth data and RTC data for the one Arduino to the other, I couldn't even find out their adresses. Thank you for your support!

Can you give a list of everything that you want to attach to an Arduino ?

9 TM1637 SevenSegment displays, do they use a clock + data ? Does that mean 9 clock pins and 9 data pins ?
HC-05 Bluetooth, do you want to use SoftwareSerial ? That causes troubles.
RTC DS3231, that's I2C.

The I2C bus is not a communication network bus. It is not that kind of "bus". Its main purpose is for sensors.
One Arduino board has to be the Master, and the others must be Slaves.
A Slave should respond quickly to a interrupt, and should therefor not use SoftwareSerial, OneWire, DHT and Neopixel libraries.
That is just one limitation, there are 10 or 20 more aspects that can cause trouble.

There is a lot of information and there are tutorials. I hope you don't mind that I don't give links to them right now. I'm afraid it will never work because it is too complex.

Can you do everything with an Arduino Mega 2560 ?

This Arduino to Arduino I2C Tutorial may be of interest.


SerialTransfer.h can be used to communicate between Arduinos using I2C