Sample Rust app for Epsilon
This is a sample Rust app to use on a NumWorks calculator. Yes, you can now use Rust to write code for a graphing calculator!
fn eadk_main() {
for _ in 0..100 {
let c = eadk::Color { rgb565: random_u16() };
let r = eadk::Rect { x: random_coordinate(), y: random_coordinate(), width: random_coordinate(), height: random_coordinate() };
eadk::display::push_rect_uniform(r, c);
}
loop {}
}Build the app
You need to install an embedded ARM toolchain as well as the corresponding rust target and a couple Python modules.
brew install rustup numworks/tap/arm-none-eabi-gcc # Or equivalent on your OS
rustup-init
rustup target add thumbv7em-none-eabihf
pip3 install lz4 pypng
cargo buildRun 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
cargo runNotes
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 cargo build. Once the corresponding binary is built on your computer, you will need to install it at address 0x90350000 in your calculator's Flash memory. The included run.py script will take care of this for you when you call cargo run.
Due to the embedded nature of Epsilon, the Rust app has to be no_std. 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 and Rust are a registered trademarks.