Crate stlog

Lightweight logging framework for resource constrained devices

Features

• O(1) runtime. Logging strings of arbitrary size takes a constant number of instructions.

• O(0) memory usage. The logged strings are NOT stored in the device memory.

• Supports different logging levels: trace, debug, info, warn and error.

Non-features

• printf style or any other kind of formatting

Limitations

• The current implementation only supports 256 different log strings. This restriction will be lifted in the future.

Requirements

The device program must be stored in ELF format.

The device linker script must allocate a .stlog section in the output ELF file as described below:

SECTIONS
{
    /* .. */

    .stlog 0 (INFO) : {
        _sstlog_trace = .;
        *(.stlog.trace*);
        _estlog_trace = .;

        _sstlog_debug = .;
        *(.stlog.debug*);
        _estlog_debug = .;

        _sstlog_info = .;
        *(.stlog.info*);
        _estlog_info = .;

        _sstlog_warn = .;
        *(.stlog.warn*);
        _estlog_warn = .;

        _sstlog_error = .;
        *(.stlog.error*);
        _estlog_error = .;
    }

    /* .. */
}

Example

• Device side

#[macro_use]
extern crate stlog;

struct Logger { .. }

impl<'a> stlog::Logger for &'a Logger { .. }

fn main() {
    let logger = Logger { .. };

    info!(&logger, "Hello, world!");
    warn!(&logger, "The quick brown fox jumps over the lazy dog.");
}

• Host side

$ # flash and execute the device program
$ arm-none-eabi-gdb /path/to/device/binary &

$ # stcat is required to decode strings logged via `stlog`
$ cargo install stcat --vers 0.1.0

$ cat /dev/ttyUSB0 | stcat -e /path/to/device/binary
INFO Hello, world!
WARN The quick brown fox jumps over the lazy dog.

Assuming that the device is logging the strings through the /dev/ttyUSB0 interface. The device binary must not be stripped.

Macros

debug
error
info
trace
warn

Traits

Logger

A logger compatible with the stlog logging framework