Adding resistors just in case tells me you did not check out what you have. What value were they, you know the schematic shows 4.7K already on the board. What are the I2C limits? I suspect the other boards have them as well. Links to each hardware device showing technical details helps. Your link to Grove was not much technical help. Research the details of each part and post a schematic, not a frizzy thing. How long are the I2C lines?
Regarding technical details, the setup is very simple. Just the Arduino board with a Grove – Base Shield. On the Grove base shield I connected the clock and the screen. Cables are short, about 20 centimetres.
Sorry for not providing good links, though that these components are quite standard.
The LCD screen technical page:
I bought the clock in Aliexpress, I do not have a lot of details other than this (what I can tell is that without the LCD connected to the I2C line the module is working fine):
VCC in Grove base is set to 5V (all components work on 5V)
Regarding the pull-up resistors, I have to admit that I am still learning... I added two 6.3K resistors between the SCL and SDA lines and 5V source.
I have the feeling that the issue is not related to the pull-up resistors, just tried to discard some options. If you think this is the way to go I can provide more details on the schematics and do more research to ensure I am adding them in the right way
You state: Regarding technical details, the setup is very simple." as we are finding it is not as simple as it appears. Yes post the Schematic, not a frizzy thing. Are the grounds of each item connected together? Do you have any test equipment available? Be sure all the I2C selects on the hardware items are sound. If you have a spare part try it and see if the problems change.
Since connecting groove modules is pretty straight forward, the problem is not the circuit. Post it anyway to rule out any doubts.
Since the modules work as intended if tested separated, the connections are not mechanically faulty.
Shall we see the code wich contains both modules? The problem might be there
Pull-up resistors shouldn't be necessary.
This is the basic schema, as giorgio says is straight forward. I am using the Grove base and standard cables. Also tried without the grove base (like in the schematics) with same results
I am running this code: Arduino Playground - I2cScanner. If the I2C scanner shows the addresses, the module works as expected. (e.g. I can run a program to set / read time)
Perhaps it is just a faulty part, what puzzles me is that the RTC works fine alone or with other I2C modules but not with the LCD
Now I2C scanner works on clock and LCD. But clock stops working after a few seconds (no response) when the LCD is connected. Without the LCD everything is working fine.
Seems that the LCD is somehow damaged or interfering with the I2C interface...
