HamChrono - HamClock reimagined for the RaspberryPi

I have started this project mainly to bring my personal desires to the great features available from HamClock. My advice is that you start there, then check out my design goals to see if this project may provide some benefit to you. I am not here to criticize HamClock, only to bring a slightly different vision to packaging the features.

HamClock by Elwood Downey WB0OEW is an Arduino and Raspberry Pi project that provides a number of useful features for amatuer radio operators. It is quite a nice tool as it is. The main limitation for Raspberry Pi users is that it comes from the Arduino world. Getting the number of features running on such a limited platform is a tour-de-force, and then porting it to the Pi is another significant achievement. The Pi is capable of much more than even the most advanced Arduino. So I became interested in seeing what I could to to unlock those features for Pi users.

Porting to modern C++.

The following are the things that I sought to do better on the Raspberry Pi:

• HamClock, like most Arduino programs (including my own), is based on an endless loop with limited or no event driven architecture. This is an appropriate design for Arduino, but on a pre-emptive multi-taksing operating system it leads to programs that run flat out without pause consuming CPU cycles, generating heat, and keeping other programs from using those cycles.
• I run HamClock on a 7 inch touch screen in a SmartyPi case. This is a great form factor for convenient deployment in the shack. At 800x400 pixels and 7 inches the screen gets very busy and using touch becomes a matter of poke and hope you hit the right spot. HamClock can be made to run on the frame buffer without a screen manager, which is a nice way to provide an appliance-like feel. Elwood has written a GUI system for HamClock that certainly gets the job done for the minimalist target Arduino system, yet another laudable achievement. But if we are building specifically for the Raspberry Pi there are frame buffer GUI libraries we can use.
• Finally I am going to port Elwood's code to modern C++ so that it may be more easily expanded and maintained, at least when run on a full multitasking OS. If you desire the minimalist system for portability, low power or other reasons, then HamClock the way Elwood wrote it is what you want.

This started off as a simple exercise to port HamClock to using the full capabilities available on a Raspberry Pi; but it has quickly become an parallel effort of that, and porting and extending NanoGui-SDL to work well, not just on a Raspberry Pi, but on the 7 inch touch display from Raspberry Pi. I will document the porting progress of each below.

Porting NanoGui-SDL

My work here is centering around making the library more targeted towards using in a 7 inch touch screen environment.

1. Supporting the Touch Screen I have provided basic support by transcoding finger touch, release and motion events to equivalent mouse events. This works, but there may be better solutions to investigate.

2. GUI Presentation In a touch environment, the active elements must be sized large enough and separated well enough to be easy to activate by a finger without a frustrating number of mistakes. NanoGui-SDL has a built in Theme system that can be used to set different program wide default values. There are also a large number of hard code values. As I identify the purpose of each I am replacing them with a Theme value.

3. Font Support The library supports True Type Fonts (TTF), but comes with three fonts bundled which are loaded in an inflexible way. I am migrating this system to one capable of using any True Type font loaded onto the system. This will be easier when Raspberry Pi OS fully supports C++17 with filesystem.

4. Smart Pointers NanoGui-SDL comes with a very nice reference counting shared pointer system wich is much better suited to a hierarchical object model than std::shared_ptr. Unfortunately it is not used as widely or consistently as I'd like; so I am extending its use where it is well suited and using std::unique_ptr and std::shared_ptr in other areas.

5. Memory Leaks The library isn't really leaky, but it does have the rather unfortunate structure that many C programmers employ: the program exit will free all remaining allocated memory. This is true, but it limits the ability of code quality tools, like Valgrind, from easily finding more important leaks. Even a small, on-going memory leak can be catastrophic to a program intended to run for very long periods of time. So I'm cleaning up everything I can track down.

Porting HamClock

1. Satellite Ephemeris Loading ephemeris from the back end is ported. Computing satellite position and predicting passes is also ported.

2. Geo Chron Display This has also been ported using Mercator projection maps loaded from image files on the file system rather than compiling map data into the binary. This latter was a very creative solution to support HamClock on an ESP device. This method is much more flexible. The day-night display is implemented by manipulating the alpha channel of the day map and drawing it on top of the night map. When computng the Azimuthal projection any image co-ordinate not "on" the earth are made transparent on both day and night maps so an interesting background may be seen "behind" the Earth. Most of the heavy lifting is done by the Graphics Co-processor and threaded which results in a very responsive program, even on a Pi 3B.

3. Full Sized Sun Images As a side benefit of using a capbable GUI library and the Graphics Co-processor the program isn't limited to displaying pre-sized thumb nails. The new program downloads the original images from the NASA website and can display them in nearly full size in a pop-up window.

New Widgets and Classes

Writing any program on top of a general purpose GUI library will eventually lead to writing new Widgets. These are the ones I have written for HamChrono.

1. TimeBox A widget to display the time and date. It is two binary mode settings (giving four separate modes):

   1. Time Zone Either GMT or the system local time zone with official Daylight Savings Time.
   2. Large or Small Either full time with seconds and date with the year, or abbreviated by omitting the seconds and year.
   3. The larger version also has a system monitor for temperature.

2. ImageDisplay Display one of a set of images loaded from the files system (or, eventually, downloaded directly) to a thumb nail area. Touch semantics for selecting an image from the set.

3. ImageRepeater Repeat the display of an image in a larger windows. Tied to an ImageDisplay.

4. ImageRepository A non-drawing object that will maintain the set of images and allow any ImageDisplay or ImageRepeater to render the image at a specified location and size. The Model-View-Controller pattern with the ImageRepository providing the model, and the ImageDisplay/Image Repeater providing the display and controller.

5. GeoChrono The heart and soul of HamClock and HamChrono. Modeled on the mechanical Geochron clock which had pride of place in my early workplaces this form of time display graphically conveys a wealth of information important to communicators. This version is modeled closely on the implementation in HamClock.

6. PassTracker A helper Widget for GeoChrono which displays the Azimuth-Elevation of objects being tracked.

7. Ephemeris Model This class manages all the ephemeris data and calculations in one location, distributing the results as needed throughout the program using callbacks.

8. Settings A class to maintain user modifiable sttings in an SQLite3 database in the users' home directory.

Dependencies

Libraries

1. I was going to use LVGL a "Light and Versitile Graphics Library". The use of this libbrary on the 7 inch RaspberryPi display is described by VK3ERW. This library needs to be compiled for the target. It was my intention to provide a package for use on the RaspberryPi. Unfortunately I found the following:

   1. No standardized build environment;
      1. Have to move Makefiles around and put your own together. There is flexibility here, but this makes keeping up with changes hard.
      2. Shared library not provided for, again you can build it yourself...
      3. Does not support common image types or file system out of the box.

2. SDL2 and NanoGUI-SDL

   1. This is very nice library, but has an incomplete and uneven feel. The developers have also become busy with other things. However, it is open source and I can fork the repository and begin taking it in the direction I need. My port of NanoGUI-SDL is included in the project.
   2. Install SDL2 on Debian derivatives: sudo apt install libsdl2-dev libsdl2-ttf-dev libsdl2-image-dev

3. SDL2_gfx a graphics primitive library that adds additional drawing capability to SDL2. Using the primitive drawing functions. Still thinking about the rest.

4. GNU CGICC a Common Gateway Interface library. This will allow my implementation to provide a RESTful API (as HamClock does) for remote control. Using the CGI interface will allow the application to be tied into a web server running on the RaspberryPi which will offload much of the configuration, security and maintenance work of a public facing access.

   1. sudo apt install libcgicc-dev

5. SOCI a C++ Database Access Library.

   1. sudo apt install libsoci-dev

6. SQLite3 QLite is a C-language library that implements a small, fast, self-contained, high-reliability, full-featured, SQL database engine.

   1. sudo apt install libsqlite3-dev

7. libcurl the multiprotocol transfer library. sudo apt-get install libcurl4-openssl-dev

   1. curlpp C++ wrapper around libcURL. sudo apt-get install libcurlpp-dev

8. C++17 compliant standard library.

   1. C++17 or better compiler package (if compiling from source).
   2. For the Raspberry Pi G++ version 8 suffices (C++14)

9. CMake version 3.10 or better (if compiling from source).

Data Sources

1. ClearSkyInstitute.Com
2. NASA
   1. NASA SDO Data
3. Entypo Font was shipped with Nanogui-SDL, I am coninuing to use it.
4. www.die.net I hope to be able to use the Moon Phases imagery found there. Either way the site deserves your attention.
5. CelesTrack NORAD Two-Line Element Sets.

73 Richard Buckley VE3YSH