rmodbus - Modbus for Rust
A framework to build fast and reliable Modbus-powered applications.
Cargo crate: https://crates.io/crates/rmodbus
What is rmodbus
rmodbus is not a yet another Modbus server. rmodbus is a set of tools to quickly build Modbus-powered applications.
Why yet another Modbus lib?
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rmodbus is transport and protocol independent
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rmodbus is platform independent
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can be easily used in blocking and async (non-blocking) applications
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tuned for speed and reliability
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provides a set of tools to easily work with Modbus context
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supports server frame processing for Modbus TCP/UDP and RTU
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server context can be easily, managed, imported and exported
So the server isn't included?
Yes, there's no server included. You build the server by your own. You choose protocol, technology and everything else. rmodbus just process frames and works with Modbus context.
Here's an example of a simple TCP blocking server:
use ;
use TcpListener;
use thread;
use ;
There are also examples for Serial-RTU and UDP in examples folder (if you're reading this text somewhere else, visit rmodbus project repository.
Modbus context
The rule is simple: one standard Modbus context per application. 10k+10k 16-bit registers and 10k+10k coils are usually more than enough. This takes about 43Kbytes of RAM, but if you need to reduce context size, download library source and change CONTEXT_SIZE constant in "context.rs".
rmodbus server context is thread-safe, easy to use and has a lot of functions.
The context is created automatically, as soon as the library is imported. No additional action is required.
Every time Modbus context is accessed, a context mutex must be locked. This slows down a performance, but guarantees that the context always has valid data after bulk-sets or after 32-bit data types were written. So make sure your application locks context only when required and only for a short period time.
There are two groups of context functions:
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High-level API: simple functions like coil_get automatically lock the context but do this every time when called. Use this for testing or if the speed is not important.
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Advanced way is to use low-level API, lock the context manually and then call proper functions, like set, set_f32 etc.
Take a look at simple PLC example:
use context;
use File;
use *;
use MutexGuard;
To let the above program communicate with outer world, Modbus server must be up and running in the separate thread, asynchronously or whatever is preferred.
Modbus client
Planned.