After a couple of weeks away I am now back on the project. In the meantime a few changes have occurred that will have a bearing on how future development progresses.
The most disruptive aspect is that the display technology I am using is going through significant change. The software drivers are being substantially updated, providing a number of very useful new features that I would like to include in my design. Amongst other things, this will permit me to use a range of different fonts for the various parts of the display. The update also brings improved performance and more mundane capabilities that will make the software easier to write, such as text alignment and the ability to determine string display size.
A further development is that, having gained experience with the current display I have decided to go for a different unit. The current unit is a single "page" display, which means that new screens have to completely overwrite the existing screen. This adds complexity when there are potentially multiple screens, e.g. Main, Menu, Configuration, etc.
I have therefore ordered a new display based on Complex Programmable Logic Device (CPLD) technology. Amongst other things, the CPLD display provides up to eight pages that can be recalled non-destructively as required. This will significantly reduce the amount of coding required. The device is on the slow boat from Hong Kong as I write this missive.
The upshot of all this is that software development is on hold pending the arrival of these new items. I therefore plan to get on with the hardware design aspects, with a view to getting the front and rear panels into the workshop for CNC milling in the next few days.