Added ADC/DAC resolution to $pinstate command, changed reported values to integer for ADC/DAC devices and float formatted for PWM devices.
Numeric settings can now be set via G65P1Q<n>S<value>, <n> is the setting number, <value> is the new value.
Changed alarm code for Modbus exceptions (communication errors) from 14 to 19.
Refactored MPG stream code to allow plugins to hook into MPG streams (via event handler).
Added _free memory system parameter, returns value in KBytes or -1 if not available from driver.
Changed basic stream data type from char to uint8_t, added HAL function and core API for releasing/closing UART streams.
Some minor bug fixes such as incorrect error code returned for unknown $-commands and temporary incorrect position reporting on in-flight G92 offset changes.
Added system parameter _tool_table_size, 0 if a tool table is not enabled.
Removed dependency on safety door input for parking settings: $41, $42, $56-$59, $392 and $393.
Removed strict dependency on spindle encoder input for spindle synced motion,
allows the use of the stepper spindle which has an implicit encoder.
Some low-level ioport improvements, added definition for virtual pins/ports.
Deprecated direct access to number of the different ioport ports in hal.port struct, use ioports_unclaimed() instead.
Removed IDLE state requirement for executing G65 macros, an error will no longer be returned and the macro will be run.
Added event handler for outputting welcome message on "native" USB connect for drivers that provides the linestate changed event.
Added support for LinuxCNC style (ABORT,<msg>) comment, requires expressions enabled. Terminates gcode program, outputs message and returns error 253.
Added PRM[<setting>] and PRM[<setting>,<bit>] functions to expressions, returns $-setting value or value of bit in integer type setting.
"hardened" flow control code, fixed bug in repeat...continue handling.
Changed signature of grbl.on_gcode_comment event, now returns status code.
Now returns no data for alarm and error enums when firmware is compiled for 128K versions of the STM32F1xx MCU.
This frees up some flash space for plugins etc.
Added $384 setting for controlling G92 offset persistence.
Improved $help command output and handling.
Moved the optional tool table in non-volatile storage.
Added gcode parameter support and optional expression support.
