I2C Examples on UNO and NANO

Development Tools IDE 1.x
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Hello
Please excuse if this has been answered before (perhaps point me to them?)

I have two UNOs, one I believe is genuine Arduino, the other I got in a "beginner's assortment".
When I connect them together via the I2C and load the slave sender example on one, and the master reader example on the other, they work as expected. (The Serial Monitor on the master reader shows "Hello Hello Hello .... (etc)"

If I load the examples on them in reverse, they both still work as expected.

I also have some NANO clones.
If I connect a NANO clone as master reader, and one of the UNOs as slave sender, they work correctly.

However, if I connect any of the NANO clones as slave sender, and one UNO as master reader they don't do anything (the LEDs don't flash and the master reader does not send anything to the Serial Monitor).

I can even connect a NANO clone as master reader, and one of the UNOs as slave sender and it works.
The only combination that does not work is NANO clone as slave sender.

My question is: if I purchase a genuine Arduino NANO or Micro, will it work as slave sender, or is there something else I don't know about?
Thanks for any help.

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44 Views so far, but no answer, so I answered my own question by purchasing a genuine Arduino Micro, and no, it does not work.

I can connect/disconnect to UNOs all day, one as Master Reader and one as Slave Sender, but connecting a Micro as Slave Sender to a UNO as Master Reader does not show anything on the Serial Monitor.

Just does not work.

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[Update] As noted above, could not get a Micro configured with the built-in example "Slave Sender" to communicate with a UNO configured as Master Reader.

Today noticed that there are also Master Sender and Slave Receiver in the examples, so configured the Micro as Master Sender and the UNO as Slave Receiver and it did not work at first. Then removed the 4.7 k pullup resistor from the SCL line and it sprang to life!

Works as expected.

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I am working on a very similar project. My Arduino Nano was sending to Uno. I am glad that you fix it and pointed out where the problem can be, as I had some issues with it before.

Thank you.