Dealing with embedded solutions you also need to deal with HMI. A majority of HMI will always be on displays so having the Raspberry PI as base is quite nice. It is very capable of supporting our GUI needs, but how do we program it?
A friend of mine uses Python with various libraries. I will do a Python demo, but I have something else in mind. I wrote an entry about the Nextion HMI solutions from www.iteadstudio.com earlier. They use a STM32 and a TFD combined with a designer. You create a HMI with objects that later can be communicated with using a serial port. I bought one of them for testing and I am quite impressed over the concept thought I will add that their solution have a few fallbacks.
I will always argue that source code must exist in human editable form. A HMI graphical design is no exception as it is source code with scripting logic embedded. I would have used XML for this purpose. The concept is not new as it has been used in various embedded solutions for years. The most common is PABX telephones with displays.
The issue with HMI is that using more advanced solutions like Qt or similar actually require a bit of knowledge. Most embedded developers or makers focus their knowledge differently and writing an advanced GUI application is often outside their comfort zone. They are simply not willing to spend the time required to master things like Qt. But, even if you master these skills you will find that solutions like Nextion take away a lot of hours if you can accepts the limitations.
I would like to put the GPU’s on Raspberry PI to some usage, but having looked into OpenGL I must admit that this is not an easy task. Using Qt makes it easier, but using Qt itself on Raspberry PI is a bit of an issue even if you forget the skillset issue most will have. Just for the record it actually exist other solutions than Qt as well.
What I would like to do is to create an advanced HMI solution for Raspberry PI using the concepts described above. You simply outline your HMI in XML that is loaded into an application that communicate with easyIPC. The Application + Your XML becomes Your HMI. Embedding this into a stand-alone executable is doable. The graphical designer part is the easy one in my case since I have made numerous flow-chart alike tools in the past. My only remaining puzle is to select a graphical library for C/C++ on Debian to build this in.