# AT-Parser-RS
A lightweight, `no_std` AT command parser library for embedded Rust applications.
[](https://crates.io/crates/at-parser-rs)
[](https://docs.rs/at-parser-rs)
[](LICENSE)
## Overview
AT-Parser-RS provides a flexible framework for implementing AT command interfaces in embedded systems. It supports the standard AT command syntax including execution, query, test, and set operations.
## Features
- `no_std` compatible - suitable for bare-metal and embedded environments
- Fixed-size response buffers via `Bytes<SIZE>` — no heap allocation
- Support for all AT command forms:
- `AT+CMD` - Execute command
- `AT+CMD?` - Query current value
- `AT+CMD=?` - Test supported values
- `AT+CMD=<args>` - Set new value(s)
- Type-safe command registration via traits
- Static command definitions (suitable for embedded/RTOS)
### Feature Flags
The library supports the following optional features:
- **`osal_rs`** - Enables integration with FreeRTOS through the [osal-rs](https://crates.io/crates/osal-rs) library for RTOS-based applications. Provides synchronization primitives like `Mutex` for thread-safe command handling.
- **`enable_panic`** - Enables a custom panic handler for `no_std` environments, providing a minimal panic implementation for embedded targets.
By default, no features are enabled, providing pure `no_std` compatibility without external dependencies.
```bash
# Build with FreeRTOS support
cargo build --features="osal_rs"
# Build with custom panic handler
cargo build --features="enable_panic"
# Build with both features
cargo build --features="osal_rs,enable_panic"
```
## Command Forms
The parser supports four standard AT command forms:
| **Execute** | `AT+CMD` | Execute an action | `AT+RST` |
| **Query** | `AT+CMD?` | Get current setting | `AT+ECHO?` |
| **Test** | `AT+CMD=?` | Get supported values | `AT+ECHO=?` |
| **Set** | `AT+CMD=<args>` | Set new value(s) | `AT+ECHO=1` |
> **Note**: All commands must start with the `AT` prefix (e.g., `AT+CMD`, not just `+CMD`). The parser expects the full AT command syntax.
## Core Types
### `AtContext<SIZE>` Trait
The main trait for implementing command handlers. The const generic `SIZE` defines the response buffer size in bytes. Override only the methods your command needs:
```rust
pub trait AtContext<const SIZE: usize> {
fn exec(&self) -> AtResult<SIZE>;
fn query(&mut self) -> AtResult<SIZE>;
fn test(&mut self) -> AtResult<SIZE>;
fn set(&mut self, args: Args) -> AtResult<SIZE>;
}
```
All methods return `Err(AtError::NotSupported)` by default.
### `AtResult<SIZE>` and `AtError`
```rust
pub type AtResult<const SIZE: usize> = Result<Bytes<SIZE>, AtError>;
pub enum AtError {
UnknownCommand, // Command not found
NotSupported, // Operation not implemented
InvalidArgs, // Invalid argument(s)
}
```
### `Bytes<SIZE>`
`Bytes<SIZE>` is a fixed-size byte buffer from `osal-rs` (re-exported by this crate) used to return responses without heap allocation:
```rust
use at_parser_rs::Bytes;
// Create from a string slice (truncated to SIZE if longer)
let response = Bytes::<64>::from_str("OK");
```
### `AtParser<T, SIZE>`
The parser is generic over both the handler type `T` and the response buffer size `SIZE`:
```rust
pub struct AtParser<'a, T, const SIZE: usize>
where
T: AtContext<SIZE> + ?Sized;
```
### `Args` Structure
Provides access to comma-separated arguments:
```rust
pub struct Args<'a> {
pub raw: &'a str,
}
impl<'a> Args<'a> {
pub fn get(&self, index: usize) -> Option<&'a str>;
}
```
## Usage Examples
### 1. Define Command Modules
Implement the `AtContext<SIZE>` trait for your command handlers. Choose a buffer size that fits your largest response string:
```rust
use at_parser_rs::context::AtContext;
use at_parser_rs::{AtResult, AtError, Args, Bytes};
const SIZE: usize = 64;
/// Echo command - returns/sets echo state
pub struct EchoModule {
pub echo: bool,
}
impl AtContext<SIZE> for EchoModule {
// Execute: return current echo state
fn exec(&self) -> AtResult<SIZE> {
if self.echo {
Ok(Bytes::from_str("ECHO: ON"))
} else {
Ok(Bytes::from_str("ECHO: OFF"))
}
}
// Query: return current echo value
fn query(&mut self) -> AtResult<SIZE> {
if self.echo { Ok(Bytes::from_str("1")) } else { Ok(Bytes::from_str("0")) }
}
// Set: enable/disable echo
fn set(&mut self, args: Args) -> AtResult<SIZE> {
let v = args.get(0).ok_or(AtError::InvalidArgs)?;
match v {
"0" => {
self.echo = false;
Ok(Bytes::from_str("ECHO OFF"))
}
"1" => {
self.echo = true;
Ok(Bytes::from_str("ECHO ON"))
}
_ => Err(AtError::InvalidArgs),
}
}
// Test: show valid values and usage
fn test(&mut self) -> AtResult<SIZE> {
Ok(Bytes::from_str("Valid values: 0 (OFF), 1 (ON)"))
}
}
/// Reset command - executes system reset
pub struct ResetModule;
impl AtContext<SIZE> for ResetModule {
fn exec(&self) -> AtResult<SIZE> {
// Trigger hardware reset
// reset_system();
Ok(Bytes::from_str("OK - System reset"))
}
fn test(&mut self) -> AtResult<SIZE> {
Ok(Bytes::from_str("Reset the system"))
}
}
```
### 2. Create Module Instances
For standard applications, create instances on the stack:
```rust
let mut echo = EchoModule { echo: false };
let mut reset = ResetModule;
```
For embedded/`no_std` environments with `static mut` (single-threaded only):
```rust
static mut ECHO: EchoModule = EchoModule { echo: false };
static mut RESET: ResetModule = ResetModule;
```
> **Note**: `static mut` requires `unsafe` blocks and is only safe in single-threaded contexts. For RTOS or multi-threaded applications, use proper synchronization primitives.
### 3. Initialize Parser and Register Commands
```rust
use at_parser_rs::parser::AtParser;
use at_parser_rs::context::AtContext;
const SIZE: usize = 64;
let mut parser: AtParser<dyn AtContext<SIZE>, SIZE> = AtParser::new();
let commands: &mut [(&str, &mut dyn AtContext<SIZE>)] = &mut [
("AT+ECHO", &mut echo),
("AT+RST", &mut reset),
];
parser.set_commands(commands);
```
### 4. Execute Commands
```rust
// Execute: show current state
match parser.execute("AT+ECHO") {
Ok(response) => println!("Response: {}", response), // "ECHO: OFF"
Err(e) => println!("Error: {:?}", e),
}
// Test: show valid values
match parser.execute("AT+ECHO=?") {
Ok(response) => println!("Valid: {}", response), // "Valid values: 0 (OFF), 1 (ON)"
Err(e) => println!("Error: {:?}", e),
}
// Set: enable echo
match parser.execute("AT+ECHO=1") {
Ok(response) => println!("Response: {}", response), // "ECHO ON"
Err(e) => println!("Error: {:?}", e),
}
// Query: get current value
match parser.execute("AT+ECHO?") {
Ok(response) => println!("Echo: {}", response), // "1"
Err(e) => println!("Error: {:?}", e),
}
// Execute reset
match parser.execute("AT+RST") {
Ok(response) => println!("Response: {}", response), // "OK - System reset"
Err(e) => println!("Error: {:?}", e),
}
// Unknown command
match parser.execute("AT+UNKNOWN") {
Ok(_) => {},
Err(AtError::UnknownCommand) => println!("Command not found"),
Err(_) => {}
}
```
`Bytes<SIZE>` implements `Display`, so it can be printed directly with `{}` or converted to a string via `.to_string()`.
## Advanced Example: UART Module
```rust
use at_parser_rs::{AtResult, AtError, Args, Bytes};
use at_parser_rs::context::AtContext;
const SIZE: usize = 64;
pub struct UartModule {
pub baudrate: u32,
pub data_bits: u8,
}
impl AtContext<SIZE> for UartModule {
// Query: return current configuration
fn query(&mut self) -> AtResult<SIZE> {
Ok(Bytes::from_str("115200,8"))
}
// Set: configure UART
fn set(&mut self, args: Args) -> AtResult<SIZE> {
let baudrate = args.get(0)
.ok_or(AtError::InvalidArgs)?
.parse::<u32>()
.map_err(|_| AtError::InvalidArgs)?;
let data_bits = args.get(1)
.ok_or(AtError::InvalidArgs)?
.parse::<u8>()
.map_err(|_| AtError::InvalidArgs)?;
if ![7, 8].contains(&data_bits) {
return Err(AtError::InvalidArgs);
}
self.baudrate = baudrate;
self.data_bits = data_bits;
// Apply configuration to hardware
// configure_uart(baudrate, data_bits);
Ok(Bytes::from_str("OK"))
}
// Test: show valid configurations and usage
fn test(&mut self) -> AtResult<SIZE> {
Ok(Bytes::from_str("AT+UART=<baudrate>,<data_bits> where baudrate: 9600-115200, data_bits: 7|8"))
}
}
```
Usage:
```rust
parser.execute("AT+UART=?"); // "AT+UART=<baudrate>,<data_bits> where..."
parser.execute("AT+UART=115200,8"); // "OK"
parser.execute("AT+UART?"); // "115200,8"
```
## Parsing Arguments
The `Args` structure provides a simple interface for accessing comma-separated arguments:
```rust
fn set(&mut self, args: Args) -> AtResult<SIZE> {
let arg0 = args.get(0).ok_or(AtError::InvalidArgs)?;
let arg1 = args.get(1).ok_or(AtError::InvalidArgs)?;
let arg2 = args.get(2); // Optional argument
// Process arguments...
Ok(Bytes::from_str("OK"))
}
```
**Important**: `Args::get()` uses 0-based indexing. For a command like `AT+CMD=foo,bar,baz`:
- `args.get(0)` returns `Some("foo")`
- `args.get(1)` returns `Some("bar")`
- `args.get(2)` returns `Some("baz")`
- `args.get(3)` returns `None`
For numeric arguments:
```rust
let value = args.get(0)
.ok_or(AtError::InvalidArgs)?
.parse::<i32>()
.map_err(|_| AtError::InvalidArgs)?;
```
## Thread Safety
### Single-threaded (bare-metal)
```rust
static mut MODULE: MyModule = MyModule::new();
// Safe in single-threaded context
```
### Multi-threaded (RTOS)
```rust
use core::cell::RefCell;
use osal_rs::sync::Mutex;
static MODULE: Mutex<RefCell<MyModule>> = Mutex::new(RefCell::new(MyModule::new()));
```
## Using the `at_modules!` Macro
The library provides an `at_modules!` macro for defining static command arrays. The first argument is the `SIZE` const:
```rust
use at_parser_rs::at_modules;
use at_parser_rs::context::AtContext;
const SIZE: usize = 64;
static mut ECHO: EchoModule = EchoModule { echo: false };
static mut RESET: ResetModule = ResetModule;
at_modules! {
SIZE;
"AT+ECHO" => ECHO,
"AT+RST" => RESET,
}
```
### Limitations and Considerations
⚠️ **Important**: This macro has significant limitations:
1. **Unsafe**: The macro creates mutable references to static data, requiring `unsafe` blocks
2. **Single-threaded only**: Not suitable for multi-threaded or RTOS environments
3. **Limited flexibility**: Cannot mix different command handler types
### Recommended Alternative
For most applications, the manual approach shown in the examples is preferred:
```rust
use at_parser_rs::context::AtContext;
use at_parser_rs::parser::AtParser;
const SIZE: usize = 64;
let mut echo = EchoModule { echo: false };
let mut reset = ResetModule;
let commands: &mut [(&str, &mut dyn AtContext<SIZE>)] = &mut [
("AT+ECHO", &mut echo),
("AT+RST", &mut reset),
];
parser.set_commands(commands);
```
This approach is safer, more flexible, and works in all contexts (stack, heap, RTOS).
## Best Practices
1. **Choose an appropriate `SIZE`**: Pick a buffer size that fits your largest response string; responses longer than `SIZE` are silently truncated
2. **Validate arguments**: Always check argument count and validity before processing
3. **Handle errors gracefully**: Use appropriate `AtError` variants for different failure modes
4. **Document test responses**: Use `test()` to provide clear usage information
5. **Minimize state**: Keep module state simple and thread-safe
## Examples
The library includes several example files demonstrating different usage patterns:
### Standard Examples
- **`complete_usage.rs`** - Complete demonstration with multiple command types (Echo, Reset, Info, LED)
- **`basic_parser.rs`** - Shows direct usage of the `AtParser` with comprehensive test cases
### Embedded/no_std Examples
These examples demonstrate code patterns suitable for `no_std` environments:
- **`embedded_basic.rs`** - Basic patterns and error handling for no_std/embedded environments
- **`embedded_error_handling.rs`** - Patterns for custom error handling and type conversions
- **`embedded_uart_config.rs`** - UART and device configuration patterns with `AtContext` implementation
> **Note**: The embedded examples are designed to show code patterns and best practices rather than being fully functional standalone programs. They demonstrate how to structure code for embedded/no_std contexts.
Run examples with:
```bash
# Standard examples (fully functional)
cargo run --example complete_usage
cargo run --example basic_parser
# Embedded examples (demonstrate patterns)
cargo run --example embedded_basic --no-default-features
cargo run --example embedded_error_handling --no-default-features
cargo run --example embedded_uart_config --no-default-features
```
## License
This project is licensed under the GNU Lesser General Public License v2.1 or later (LGPL-2.1-or-later) - see the [LICENSE](LICENSE) file for details.