Here is the beta version of the Diagnostic Software. It should at least get you started. Some instructions are in the README.MD file in the top directory.
Only main menu items 1 and 2 are implemented at this stage (core I2C tests and Analog I/Os).
I need to write a manual for this but I have been too busy coding it so that you could assess your Arduino..hihi
The main menu number 2 (Analogue inputs), brings a second level menu for testing the encoder inputs, the push button, the PTT, the Keyer and the spare analogue input.
Results are displayed in a horizontal bar graph with a scale from 0 to 5V representing the value read by the inputs. That way you can see how it matches the values your voltmeter indicates on the respective pin.
Results are shown only on changes to the values read, for example when rotating the encoder, pushing the PTT or the encoder push-button etc...
If no results are shown then your Arduino cannot read analogue inputs and it would mean plan-B unfortunately.
Let me know how you go with it.
All the best,
73, John (VK2ETA)