# RPi SIM868
[](https://crates.io/crates/rpi_sim868)
[](LICENSE)
[](https://blog.rust-lang.org/2021/10/21/Rust-1.56.0.html)
### [Documentation](https://docs.rs/rpi_sim868)
RPi SIM868 is a Rust crate designed to simplify interaction with the [Waveshare SIM868 HAT](https://www.waveshare.com/gsm-gprs-gnss-hat.htm) for Raspberry Pi. It utilizes the [Tokio](https://tokio.rs) runtime for managing asynchronous tasks and includes its own task scheduler based on a priority queue.
Each method call initiates a new task, which is enqueued with a priority to ensure swift execution as soon as the serial port becomes available.
Methods (except for `HAT::turn_on`) return `TaskJoinHandle`, where `T` represents the type resulting from parsing and analyzing the serial output, if applicable. Tasks related to phone calls are treated as first-class citizens with high priority, reducing delays in answering or concluding calls.
RPi SIM868 was conceived following a high-altitude balloon launch where the HAT served as a backup tracking device. The initial software, written in Python, lacked the performance and safety synonymous with Rust.
### Tested SIM868 UART selection switch:
- **A** - `ttyUSBx` port
- **B** - `ttySx` port.
### Tested devices:
- RPi 3 Model B
- RPi 4 Model B
- RPi Zero W
- RPi Zero 2 W.