- Feature: Realtime feed, rapid, and spindle speed overrides. These
alter the running machine state within tens of milliseconds!
    - Feed override: 100%, +/-10%, +/-1% commands with values 1-200% of
programmed feed
    - Rapid override: 100%, 50%, 25% rapid rate commands
    - Spindle speed override: 100%, +/-10%, +/-1% commands with values
50-200% of programmed speed
    - Override values have configurable limits and increments in
config.h.
- Feature: Realtime toggle overrides for spindle stop, flood coolant,
and optionally mist coolant
    - Spindle stop: Enables and disables spindle during a feed hold.
Automatically restores last spindles state.
    - Flood and mist coolant: Immediately toggles coolant state until
next toggle or g-code coolant command.
- Feature: Jogging mode! Incremental and absolute modes supported.
    - Grbl accepts jogging-specific commands like $J=X100F50. An axis
word and feed rate are required. G20/21 and G90/G91 commands are
accepted.
    - Jog motions can be canceled at any time by a feed hold `!`
command. The buffer is automatically flushed. (No resetting required).
    - Jog motions do not alter the g-code parser state so GUIs don’t
have to track what they changed and correct it.
- Feature: Laser mode setting. Allows Grbl to execute continuous
motions with spindle speed and state changes.
- Feature: Significantly improved status reports. Overhauled to cram in
more meaningful data and still make it smaller on average.
    - All available data is now sent by default, but does not appear if
it doesn’t change or is not active.
    - Machine position(MPos) or work position(WPos) is reported but not
both at the same time. Instead, the work coordinate offsets (WCO)are
sent intermittently whenever it changes or refreshes after 10-30 status
reports. Position vectors are easily computed by WPos  = MPos - WCO.
    - All data has changed in some way. Details of changes are in the
markdown documents and wiki.
- Feature: 16 new realtime commands to control overrides. All in
extended-ASCII character space.
    - While they are not easily typeable and requires a GUI, they can’t
be accidentally triggered by some latent character in the g-code
program and have tons of room for expansion.
- Feature: New substates for HOLD and SAFETY DOOR. A `:x` is appended
to the state, where `x` is an integer and indicates a substate.
    - For example, each integer of a door state describes in what phase
the machine is in during parking. Substates are detailed in the
documentation.
- Feature: With the alarm codes, homing and probe alarms have been
expanded with more codes to provide more exact feedback on what caused
the alarm.
- Feature: New hard limit check upon power-up or reset. If detected, a
feedback message to check the limit switches sent immediately after the
welcome message.
    - May be disabled in config.h.

- OEM feature: Enable/disable `$RST=` individual commands based on
desired behavior in config.h.
- OEM feature: Configurable EEPROM wipe to prevent certain data from
being deleted during firmware upgrade to a new settings version or
`RST=*` command.
- OEM feature: Enable/disable the `$I=` build info write string with
external EEPROM write example sketch.
    - This prevents a user from altering the build info string in
EEPROM. This requires the vendor to write the string to EEPROM via
external means. An Arduino example sketch is provided to accomplish
this. This would be useful for contain product data that is
retrievable.

- Tweak: All feedback has been drastically trimmed to free up flash
space for the v1.0 release.
    - The `$` help message is just one string, listing available
commands.
    - The `$$` settings printout no longer includes descriptions. Only
the setting values. (Sorry it’s this or remove overrides!)
    - Grbl `error:` and `ALARM:` responses now only contain codes. No
descriptions. All codes are explained in documentation.
    - Grbl’s old feedback style may be restored via a config.h, but
keep in mind that it will likely not fit into the Arduino’s flash space.
- Tweak: Grbl now forces a buffer sync or stop motion whenever a g-code
command needs to update and write a value to EEPROM or changes the work
coordinate offset.
    - This addresses two old issues in all prior Grbl versions. First,
an EEPROM write requires interrupts to be disabled, including stepper
and serial comm. Steps can be lost and data can be corrupted. Second,
the work position may not be correlated to the actual machine position,
since machine position is derived from the actual current execution
state, while work position is based on the g-code parser offset state.
They are usually not in sync and the parser state is several motions
behind. This forced sync ensures work and machine positions are always
correct.
    - This behavior can be disabled through a config.h option, but it’s
not recommended to do so.
- Tweak: To make status reports standardized, users can no longer
change what is reported via status report mask, except for only
toggling machine or work positions.
    - All other data fields are included in the report and can only be
disabled through the config.h file. It’s not recommended to alter this,
because GUIs will be expecting this data to be present and may not be
compatible.
- Tweak: Homing cycle and parking motion no longer report a negative
line number in a status report. These will now not report a line number
at all.
- Tweak: New `[Restoring spindle]` message when restoring from a
spindle stop override. Provides feedback what Grbl is doing while the
spindle is powering up and a 4.0 second delay is enforced.
- Tweak: Override values are reset to 100% upon M2/30. This behavior
can be disabled in config.h
- Tweak: The planner buffer size has been reduced from 18 to 16 to free
up RAM for tracking and controlling overrides.
- Tweak: TX buffer size has been increased from 64 to 90 bytes to
improve status reporting and overall performance.
- Tweak: Removed the MOTION CANCEL state. It was redundant and didn’t
affect Grbl’s overall operation by doing so.
- Tweak: Grbl’s serial buffer increased by +1 internally, such that 128
bytes means 128, not 127 due to the ring buffer implementation. Long
overdue.
- Tweak: Altered sys.alarm variable to be set by alarm codes, rather
than bit flags. Simplified how it worked overall.
- Tweak: Planner buffer and serial RX buffer usage has been combined in
the status reports.
- Tweak: Pin state reporting has been refactored to report only the
pins “triggered” and nothing when not “triggered”.
- Tweak: Current machine rate or speed is now included in every report.
- Tweak: The work coordinate offset (WCO) and override states only need
to be refreshed intermittently or reported when they change. The
refresh rates may be altered for each in the config.h file with
different idle and busy rates to lessen Grbl’s load during a job.
- Tweak: For temporary compatibility to existing GUIs until they are
updated, an option to revert back to the old style status reports is
available in config.h, but not recommended for long term use.
- Tweak: Removed old limit pin state reporting option from config.h in
lieu of new status report that includes them.
- Tweak: Updated the defaults.h file to include laser mode, altered
status report mask, and fix an issue with a missing invert probe pin
default.

- Refactor: Changed how planner line data is generated and passed to
the planner and onto the step generator. By making it a struct
variable, this saved significant flash space.
- Refactor: Major re-factoring of the planner to incorporate override
values and allow for re-calculations fast enough to immediately take
effect during operation. No small feat.
- Refactor: Re-factored the step segment generator for re-computing new
override states.
- Refactor: Re-factored spindle_control.c to accommodate the spindle
speed overrides and laser mode.
- Refactor: Re-factored parts of the codebase for a new jogging mode.
Still under development though and slated to be part of the official
v1.0 release. Hang tight.
- Refactor: Created functions for computing a unit vector and value
limiting based on axis maximums to free up more flash.
- Refactor: The spindle PWM is now set directly inside of the stepper
ISR as it loads new step segments.
- Refactor: Moved machine travel checks out of soft limits function
into its own since jogging uses this too.
- Refactor: Removed coolant_stop() and combined with
coolant_set_state().
- Refactor: The serial RX ISR forks off extended ASCII values to
quickly assess the new override realtime commands.
- Refactor: Altered some names of the step control flags.
- Refactor: Improved efficiency of the serial RX get buffer count
function.
- Refactor: Saved significant flash by removing and combining print
functions. Namely the uint8 base10 and base2 functions.
- Refactor: Moved the probe state check in the main stepper ISR to
improve its efficiency.
- Refactor: Single character printPgmStrings() went converted to direct
serial_write() commands to save significant flash space.

- Documentation: Detailed Markdown documents on error codes, alarm
codes, messages, new real-time commands, new status reports, and how
jogging works. More to come later and will be posted on the Wiki as
well.
- Documentation: CSV files for quick importing of Grbl error and alarm
codes.

- Bug Fix: Applied v0.9 master fixes to CoreXY homing.
- Bug Fix: The print float function would cause Grbl to crash if a
value was 1e6 or greater. Increased the buffer by 3 bytes to help
prevent this in the future.
- Bug Fix: Build info and startup string EEPROM restoring was not
writing the checksum value.
- Bug Fix: Corrected an issue with safety door restoring the proper
spindle and coolant state. It worked before, but breaks with laser mode
that can continually change spindle state per planner block.
- Bug Fix: Move system position and probe position arrays out of the
system_t struct. Ran into some compiling errors that were hard to track
down as to why. Moving them out fixed it.