The logging library provides a flexible way to trace execution of Arduino programs.
I created this library because I could not find another solution that met
my needs. It is inspired by log4j but is designed to work within the
limitations of the Arduino platform.
logging::StandardFormatter;
logging::SerialAppender appender(Serial, logging::Level::info, &formatter);
logging::Logger::ROOT->add_appender(&appender);
static logging::Logger logger(__FILE__, logging::Level::info);
LOG_INFO(logger, "Hello %s world", "logging");
logger.info() << F("Hello, World ") << std::endl;
logger.info(__LINE__) << F("Hello, World ") << std::endl;
You can attach multiple appenders to any logger to send output to several
places. I have a bluetooth card attached to Serial3 so I define a
SerialAppender for Serial (usb) and Serial3 (bluetooth) so log output
goes to my phone or the host computer or both. An SdAppender sends
log output to files on the microSD card on pin 53. My clock card works
as a TimeSource to supply unix time to a TimestampFormatter so everything
has date and time. You will need to install a clock card and include
the DS3231 library for TimestampFormatter to work.
The SdAppender sends output to files on a microSD card. You will need to include
extra libraries for this to work: SD, SPI and Wire. The SD library defines
a 500 byte buffer so this appender increases the sram usage significantly.
Normally all the appenders are attached to the root logger which is
the parent of all other loggers. However, there is nothing special about the
root logger, except that it is is the default parent of new loggers. You can
construct loggers with explicit parent loggers or supply nullptr to make a new
root logger. For example, I have one logger with no parent logger which
is connected to a single SerialAppender to avoid the delays associated
with file logging.
Configuration can be done in the setup function of your sketch. Be sure
to allocate objects in the heap rather than the stack, so they
won't be deleted when the setup function returns.
New formatters and appenders are easy to define. Use the source code for examples.
Suggestions, requests and contributions are welcome. I have a limited experience with Arduino, so there are probably many ways this can be improved. If you want to fix something, feel free to open a pull request and send me email.
This version does not include any configuration mechanism so you need to create and link all the objects manually.
The clock and microSD interfaces are based on the specific hardware I have available. If I learn of more standardized interfaces I might incorporate those into some future version to be compatible with more hardware varieties.
Internal buffers are shared to minimize the amount of sram required for logging, so it is not re-entrant.
Information from many websites has been used in preparation of this library, too many to list.
Implementation of the C++ style stream logging benefited from http://www.angelikalanger.com/Articles/C++Report/IOStreamsDerivation/IOStreamsDerivation.html and https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html.
Jeroen F.J. Laros reviewed the code and provided useful feedback.
The overall concept is based on log4j and log4cxx. Ideas from the Python logging library has also been incorporated.