#message #wireless #lora #data #protocols #parts #networking

no-std bin+lib orouter-wireless

Implementation of wireless protocol for Overline network

1 unstable release

0.1.1 Dec 5, 2023
0.1.0 Dec 4, 2023

#9 in #lora

MIT license

39KB
646 lines

orouter-wireless (ōRouter wireless protocol)

Defines and implements protocol used on oRouter's physical radio layer (now using LoRa)

Application level message can be theoretically unlimited, but LoRa can only transmit 255B in one message. This protocol takes care of splitting message to appropriate number of parts with necessary added information allowing in to be joined back on receiving end when all parts arrive.

crate::MessageSlicer takes care of the splitting part and is used before the data is transmitted using oRouter. crate::MessagePool is used on receiving end to put parts of the application level / logical message together to form the original message back. Note that the parts don't have to arrive in order, only that all parts of the message have to arrive eventually.

crate::WirelessMessagePart represents raw chunk of data transmitted/received using oRouters radio chip. This crate implements and uses following scheme for message part:

name length in bytes description
network bytes 2 network bytes. always 0xAA 0xCC (will be configurable in next release)
hash 6 hash - first 3B are random, second 3B form a prefix grouping parts of the message to one
part_num 1 part number 1, 2 or 3 (only 3-part messages supported)
total_count 1 total count of messages with this prefix
length 1 length of data
msg type 1 overline message type
data type 1 byte identifying data type, if previous field is data
data 1 - 240 actual data
CRC16 2 CRC16 of the whole message (header + data)

Example of using a crate::MessageSlicer to split some data for wireless transmission:

use orouter_wireless::{MessageSlicer, MessageType, network};

fn main() {
    // VVV in practice provide a good random seed here VVV
    let mut slicer = orouter_wireless::MessageSlicer::new(1234u64, network::DEFAULT);
    let messages = slicer
        .slice(&[0xc0, 0xff, 0xee], MessageType::Data, 0x01).unwrap();
    println!("slices = {:?}", messages);
}

Example of using a crate::MessagePool to assemble data back from received message parts:

use orouter_wireless::MessagePool;

fn main() {
    let mut message_pool = MessagePool::default();
    // this represents a message part received from oRouter
    //
    // in this example, there is 1 part of total 1 forming the whole message, because the data
    // contained in the message are short
    for part in vec![
        vec![
            0xaa, 0xcc, 0x1b, 0xf2, 0x73, 0x86, 0x80, 0xe1, 0x01, 0x01,
            0x05, 0x01, 0x01, 0x41, 0x48, 0x4f, 0x59, 0x21, 0x53, 0xef
        ]
    ] {
        match message_pool.try_insert(part.clone()) {
            Ok(Some(message)) => assert_eq!(message.data(), b"AHOY!"),
            Ok(None) => {}
            Err(_) => {
                eprintln!(
                    "error while trying to insert message = {:02x?}",
                    part
                )
            }
        }
    }
}

Dependencies

~22–710KB
~13K SLoC