Basic Message Logger

[EvanLF6768]

A simple interface for logging messages to a serial console with a printf like API to act as the complete bare minimum for logging. In future, something more advanced such as WPILog to facilitate namespaces and datalogging would be preferred.

Frontend

printf-like

// Get the primary logger singleton
auto log = Logging::GetLog();
// The different functions are different log levels
log.Trace("Super verbose information which isn't very important during normal operation, only enabled in debug builds");
log.Debug("Slightly more important information which should not exist during normal operation, only enabled in debug builds");
log.Info("General details which do not imply there is an issue");
log.Warn("Something strange might be going on (eg. a secondary sensor is not connected), but all subsystems can continue to operate");
log.Error("A subsystem has failed");
log.Fatal("Core components cannot operate");

// Specify the level through an enum instead
log.LogMessage(Logging::Level::kWarn, "Can be used for variable log levels");

// Specify format arguments
log.Info("The meaning of life: {}", 42);

RAII Output Iterator

The printf like API will likely be written in terms of this.

{
    // Create a new message handle
    auto msg = Logging::GetLog().MessageBuilder(Logging::Level::kWarn);
    // Write a single character
    *msg++ = 'F';
    // Use format
    std::format_to(msg, "Hello {}", "World!");
    // Message is committed at the end of the scope
}

Metadata

To the beginning of each message the following should be appended:

• Timestamp (seconds since boot to the nearest microsecond)
• Level
• Current FreeRTOS task
  At the end of the message a newline and a null character (acting as an end of message sentinal) should be appended.

For example Warn("foo {}", 42) could become something like [13.894662|WARN|MyTask] foo 42\n\0.

Backend

Messages should be written to an arbitrary number of OutputPort objects. An implementation for a USB VCOM port should be written.

Checkpoints

• Freestanding Hello World via USB VCOM
• Logging::GetLog() and temporary proof of concept function log.RawMessage(str) which directly sends the message with no metadata, formatting or use of OutputPort abstraction
• Extract USB code into an OutputPort object, unit testing
• MessageBuilder without log levels or metadata
• Log levels (no other metadata) and all frontend functions
• Timestamp and current task