* Add MAX7219_DEBUG to Travis CI testing
* Tweak config and use standard pin naming for MAX7219_DEBUG
* MAX7219: Apply coding standards, use macros, etc.
* Make code work...
* Add Max7219 LED Matrix Debug Support
The Max7219 8x8 LED Matrix's are very helpful for debugging new code.
And for that matter, just trying to maximize printer settings without
causing stuttering.
The displays are very inexpensive (under $2.00 with shipping) and
provide a lot of help when trying to debug complicated code.
* Try to keep Makefile up to date.
When M405 is used it changes 'volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]' value. When M406 disables M405 it leaves the value unchanged.
This PR applies 'calculate_volumetric_multipliers' in M406 instead of resetting it to 1.0 because M200 may not be compatible with M405 hence I'm sure to restore anyway with correct value.
#7504 integration has missed this part.
When more than 1 servo is used with bltouch it's impossible to predefine default servo delay for it.
In my original fix I completely removed this part but maybe this is a better compromise
Enforcing requirements so XON/XOFF software handshake works and no drops of data are experienced while transferring data to an SD Card. I tested this with a CH340 USB to serial adapter (quite typical) at baudrates as high as 1000000 on a Atmega2560 running at 16Mhz, with no problems at all. We need a 1024 byte RX buffer. Less than that and we will have drops, higher than that is not needed