Solved: LCD 1602 works fine plugged directly to UNO but not wired separately.?

A 1602A LCD unit attached to an adafruit i2c 16x2 RGB shield works fine plugged directly
into a UNO WiFi Rev2 but not when wired with jumper wires. The jumper wires have been ohmed out OK with a meter. There are two data lines (A4 & A5) and 5+ and GND.

Is there additional pins possibly being used by the shield plugged in directly to the UNO?

appreciate any input....

edit - the adafruit website:
pertains to UNO, NOT UNO WiFi Rev2.

try to connect all three GND lines.
If this is not sufficent start adding line by line ...

How long are these wires? Anything over 1000m and you will have problems...

A photo of what you have done might help, as would a schematic. A photo should clearly show how it is wired.

"How long are these wires? Anything over 1000m and you will have problems.."

A 1000 meters? Lol.. These are 6 inches/ 15 cm long.
All 4 wire connections are verified.

6" is fine, but you didn't say so we have no way of knowing!

Well, if you want help you have to provide the information requested, of course you don't have to provide it, but neither does anyone have to help.

Added the other two ground points with no change. A screw shield is probably my next best option as that gives me a termination point for field sensors/control wiring.

You could try swapping out the jumper wires for new ones in case they have a bad connection inside the wire.

They ohmed out fine but I have changed them.

Check the schematic of the UNO WiFi Rev2. I'm reasonably sure (not behind a PC at the moment) that A4 and A5 are not the I2C pins. Use the dedicated pins near pin 13.


The diagram on the adafruit website:

The picture shows a UNO wiring pictorial, NOT for a UNO WiFi Rev2. The WiFi Rev2 has
separate SCL & SDA pins on it on the Digital Input side of the board.

Live and learn.....

I just discovered that reality a short while ago. Thanks for your input.

Because the UNO WiFi Rev2 is actually not related to the UNO in any meaningful way. :cold_sweat: Just a confusing naming.

Completely different processor! :wink:

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