Option to format timestamp as [ HH:MM:SS.MMM ]

[MattStarfield]

Showing the timestamp as a raw ms count can be helpful for doing time-math, but for visual inspection, it can be much easier to have the timestamp formatted as something like [ HH:MM:SS.MMM ]. For more than 100 hours, an extra H digit can be added.

I suggest the addition of a format switch function, something like formatTimestampOn();

[MattStarfield]

If it's helpful, here's how I implemented this in my own application...

I have this function:

// return a millisecond value as a string formatted as "HH:MM:SS.mmm"
    char  formattedMillisBuffer[17];                                 // global char buffer for the printing of milliseconds in formatted time
    char* getFormattedMillisString(uint32_t msCount)
    {
      uint16_t milliseconds  = msCount % 1000;          // ms remaining when converted to seconds
      uint16_t allSeconds   = msCount / 1000;           // total number of seconds to calculate remaining values

      uint16_t hours            = allSeconds / 3600;    // convert seconds to hours
      uint16_t secondsRemaining = allSeconds % 3600;    // seconds left over

      uint16_t minutes  = secondsRemaining / 60 ;       // convert seconds left over to minutes
      uint16_t seconds  = secondsRemaining % 60;        // seconds left over

      snprintf(formattedMillisBuffer, sizeof(formattedMillisBuffer),           // "prints" formatted output to a char array (string)
                "%02d:"   //HH:
                "%02d:"   //MM:
                "%02d."   //SS.
                "%03d"    //MMM
                ,
                hours,
                minutes,
                seconds,
                milliseconds
            );

      return formattedMillisBuffer;

    } // END -- getFormattedMillisString()

which I'm calling like this

// add print of Debug Mode if debugLevel is at or above DBG_INFO
// use Serial.print instead of Debug.print() to ignore the state of Debug.timestampXX()
    if(DEBUG_MODE_DEFAULT >= DBG_INFO)
    {
       // Print formatted time
       Serial.print(F("["));
       Serial.print(getFormattedMillisString(millis()));
       Serial.print(F("] "));
       Serial.print(F("debug message\n\r"));
    }

in place of:

Debug.print(DBG_INFO,    F("debug message") );

the "formatted time" debug message looks like this:

[00:00:02.823] debug message

which is helpful because it aligns all of the times and message text to fixed widths, making the debug output more pleasant and readable.