Using LogHandler to log to an SD Card with SdFat library

Firmware
1

I am trying to create/adapt my own LogHandler to log to an SD card using the SdFat library. I have taken inspiration from the Papertrial LogHandler, as C++ is not my first language…

A few issues/questions have come up, and I was hoping for some guidance/thoughts/ideas.

Inheritance questions for inputs

Assume I’ve created a new class which starts out something like this:

class SdLogHandler : public LogHandler {
    String m_system;

    public SdLogHandler(String system = System.deviceID(), LogLevel level = LOG_LEVEL_INFO, const LogCategoryFilters &filters = {});
    virtual ~SdLogHandler();

...
}

When I try to use the same inputs as used in the SerialLogHandler example (with loglevels and filters), I get the error: “no matching function for call to ‘SdLogHandler::SdLogHandler(LogLevel)’”. Why is this the case?

Alternatives to Global Variables

To enable the use of the SdFat library for SD use across multiple files, I set the instance of SdFat as a global variable. Is there a better way to do this? Is it possible to create multiple instances of SdFat for use on 1 SD Card? I plan to use the same SD card for logging data and info/bugs…

Any recommendations are greatly appreciated. I can also update with more code if helpful.

2

Default parameters can only be omitted from the end forward, but in your case you want to provide the middle paramter and omit the first and last - that is not allowed in C++.

To do what you want you need to have a seperate constructor (overload) that takes the log level as first (or only) parameter.

1 Like