Sample C++ app for Epsilon

This is a sample C++ app to use on a NumWorks calculator.

using namespace EADK;

void eadk_main() {
  Display::pushRectUniform(
    Display::Rect(0, 0, 320, 240),
    Display::Color(0x000000)
  );
  while (1) {
    Keyboard::State kbd = Keyboard::scan();
    if (kbd.keyDown(Keyboard::Key::OK)) {
      spaceship.createRockets();
    }
    if (kbd.keyDown(Keyboard::Key::Up)) {
      spaceship.move(0, -Spaceship::k_step);
    }
    refreshScene();
  }
}

Build the app

You need to install an embedded ARM toolchain and a couple Python modules.

brew install numworks/tap/arm-none-eabi-gcc # Or equivalent on your OS
pip3 install lz4 pypng
make clean && make build

Run the app

The app is sent over to the calculator using the DFU protocol over USB.

brew install dfu-util # Or equivalent on your OS
# Now connect your NumWorks calculator to your computer using the USB cable
make run

Notes

The NumWorks calculator runs Epsilon, a tailor-made calculator operating system. Starting from version 16, Epsilon allows installing custom binary apps. To run this sample app, make sure your calculator is up-to-date by visiting https://my.numworks.com. Note that at the moment Epsilon 16 is in beta, so you'll need to register as a beta tester.

Epsilon expects apps to follow a certain layout in memory. Namely, they should start with the following header:

Offset	Size	Value	Description
0x00	0x04	0xDEC0BEBA	Magic start-of-header marker
0x04	0x04	0x00000000	API Level
0x08	0x04	-	Offset from start of the app to a NULL-terminated NFKD UTF-8 string containing the app name
0x0C	0x04	-	Size of the icon data
0x10	0x04	-	Offset from start of the app to the actual icon data. This data should be the result of LZ4-compressing a sequence of 55x56 RGB565 pixels
0x14	0x04	-	Offset from start of the app to the entry point.
0x18	0x04	-	Size of the entire app
0x22	0x04	0xDEC0BEBA	Magic end-of-header marker

Generating the appropriate header is taken care of by a linker script when you run make build. Once the corresponding binary is built on your computer, you will need to install it at address 0x90350000 and 0x90750000 in your calculator's Flash memory. The included run.py script will take care of this for you when you call make run.

Due to the embedded nature of Epsilon, this C++ app is built using -ffreestanding -nostdinc -nostdlib. The interface that an app can use to interact with the OS is essentially a short list of system calls. Feel free to browse the code of Epsilon itself if you want to get an in-depth look.

Please note that any custom app is removed when resetting the calculator.

License

This sample app is distributed under the terms of the BSD License. See LICENSE for details.

Trademarks

NumWorks is a registered trademark.

czadikem / epsilon-sample-app-cpp