Log¶

Note

Under construction.

The Log module is an API for outputting logs from applications. Output logs are stored in the system's log buffer and also flow to UART and the console (if connected).

Output Methods¶

Log.error("something failed")
Log.warn("low battery")
Log.info("user clicked")
Log.debug("x=#{x}")

Short forms are also available:

Log.e("err")
Log.w("warn")
Log.i("info")
Log.d("debug")

Tagged Output (2-argument form)¶

You can pass a tag as the first argument and a message as the second.

Log.info("MyApp", "started")
Log.error("Net", "connection refused")

Method	Signature
`Log.error(msg)` / `Log.error(tag, msg)`	Error
`Log.warn(msg)` / `Log.warn(tag, msg)`	Warning
`Log.info(msg)` / `Log.info(tag, msg)`	Info
`Log.debug(msg)` / `Log.debug(tag, msg)`	Debug
`Log.e` / `Log.w` / `Log.i` / `Log.d`	Short forms of the above

Level Constants¶

Constant	Value
`Log::LEVEL_NONE`	0
`Log::LEVEL_ERROR`	1
`Log::LEVEL_WARN`	2
`Log::LEVEL_INFO`	3
`Log::LEVEL_DEBUG`	4
`Log::LEVEL_VERBOSE`	5

Level Control¶

Log.set_level(Log::LEVEL_INFO)             # Set overall level to INFO and above
Log.set_level_for_tag("MyApp", Log::LEVEL_DEBUG)  # Override per tag

Method	Purpose
`Log.set_level(level)`	Set overall log level
`Log.set_level_for_tag(tag, level)`	Override level for a specific tag

Buffer Access¶

Logs are kept in a ring buffer and can be read back later. This is useful when writing apps like a Log Viewer.

Method	Return Value
`Log.read_lines(max_lines = nil, level = nil)`	Array of lines
`Log.write_pos`	Current write position (sequence number)
`Log.set_buffer_level(level_str)`	Set the level retained in the buffer
`Log.buffer_level`	Get the buffer level

lines = Log.read_lines(20)   # Last 20 lines
lines.each { |line| puts line }

Sample¶

class MyApp < FmrbApp
  TAG = "MyApp"

  def on_create
    Log.info(TAG, "started, name=#{@name}")
  end

  def on_event(ev)
    super
    Log.debug(TAG, "event=#{ev[:type]}")
  end

  def on_destroy
    Log.info(TAG, "stopped")
  end
end

Notes¶

Log output overhead

Using Log.debug in frequently called places like on_update consumes CPU and UART bandwidth. In production, it is recommended to limit logging to LEVEL_INFO and above.