I have a watt meter that has a main PCB and a 16 pin (16x02) display (not arduino)
I took the display apart from the PCB and made a 16 wire extension chord to have the display separate from the main board with all the heavy wiring and it works well but it's too messy having a wide 16 wire strip going into the display.
So...I found this display on eBay (with an arduino serial interface):
and was wondering if I can solder the same module to the main PCB's 16 pin to have the support for a serial connection: https://goo.gl/uTG9uF
The software for your power meter will need to be changed to support the new display as the display 'backpack' most likely uses a completely different technology from what is currently implemented. Unless you have access to the source code, this will not be possible.
I2C is not designed for long distances. It works very well for connecting integrated circuits on the same pcb. Or for a short (150mm) external bus cable.
You have no knowledge of the firmware on your proprietary wattmeter.
Yes, you could "sniff" the 16 pins to determine what the software is writing to the LCD.
Then convert this data to RS232 or RS485 with appropriate driver chips. These protocols are designed for longer distances.
Then convert this data back into LCD commands at your remote site.
This would involve an MCU and electronics at your wattmeter. A long cable. Another MCU and electronics at your remote LCD.
Oh, and the "sniffer" software is a little fiddly.
What distance is between your wattmeter and remote LCD?
Incidentally, your 16 pins are unlikely to all be used. I suspect that only 9 are necessary. 10-way ribbon cable is ok for 1000mm or so.
Is there a way to do it without software and complex stuff? (everything is complex for me as I have never messed with arduinos), something like one tiny module for the display and one for the main PCB.