diff --git a/CMakeLists.txt b/CMakeLists.txt
index 230010f..4f2e121 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,6 +21,8 @@ target_sources(grbl INTERFACE
  ${CMAKE_CURRENT_LIST_DIR}/stepper.c
  ${CMAKE_CURRENT_LIST_DIR}/system.c
  ${CMAKE_CURRENT_LIST_DIR}/tool_change.c
+ ${CMAKE_CURRENT_LIST_DIR}/alarms.c
+ ${CMAKE_CURRENT_LIST_DIR}/errors.c
 )
 
 target_include_directories(grbl INTERFACE ${CMAKE_CURRENT_LIST_DIR})
diff --git a/README.md b/README.md
index 64c6bf9..016b008 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ It has been written to complement grblHAL and has features such as proper keyboa
 
 ---
 
-Latest build date is 20210819, see the [changelog](changelog.md) for details.  
+Latest build date is 20210907, see the [changelog](changelog.md) for details.  
 __NOTE:__ Drivers built with more than three axes configured \(`N_AXIS` > `3`\) will force a settings reset when upgraded. Backup and restore of settings is recommended for these.
 
 ---
@@ -77,5 +77,7 @@ List of Supported G-Codes:
   *** number of outputs supported dependent on driver implementation.
 ```
 
+Some [plugins](https://github.com/grblHAL/plugins) implements additional M-codes.
+
 ---
-2021-07-26
+2021-09-08
diff --git a/alarms.c b/alarms.c
new file mode 100644
index 0000000..35ce01e
--- /dev/null
+++ b/alarms.c
@@ -0,0 +1,59 @@
+/*
+  alarms.c -
+
+  Part of grblHAL
+
+  Copyright (c) 2017-2021 Terje Io
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
+  Copyright (c) 2009-2011 Simen Svale Skogsrud
+
+  Grbl is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Grbl is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdint.h>
+
+#include "grbl.h"
+#include "core_handlers.h"
+
+PROGMEM static const alarm_detail_t alarm_detail[] = {
+    { Alarm_HardLimit, "Hard limit", "Hard limit has been triggered. Machine position is likely lost due to sudden halt. Re-homing is highly recommended." },
+    { Alarm_SoftLimit, "Soft limit", "Soft limit alarm. G-code motion target exceeds machine travel. Machine position retained. Alarm may be safely unlocked." },
+    { Alarm_AbortCycle, "Abort during cycle", "Reset while in motion. Machine position is likely lost due to sudden halt. Re-homing is highly recommended." },
+    { Alarm_ProbeFailInitial, "Probe fail", "Probe fail. Probe is not in the expected initial state before starting probe cycle when G38.2 and G38.3 is not triggered and G38.4 and G38.5 is triggered." },
+    { Alarm_ProbeFailContact, "Probe fail", "Probe fail. Probe did not contact the workpiece within the programmed travel for G38.2 and G38.4." },
+    { Alarm_HomingFailReset, "Homing fail", "Homing fail. The active homing cycle was reset." },
+    { Alarm_HomingFailDoor, "Homing fail", "Homing fail. Safety door was opened during homing cycle." },
+    { Alarm_FailPulloff, "Homing fail", "Homing fail. Pull off travel failed to clear limit switch. Try increasing pull-off setting or check wiring." },
+    { Alarm_HomingFailApproach, "Homing fail", "Homing fail. Could not find limit switch within search distances. Try increasing max travel, decreasing pull-off distance, or check wiring." },
+    { Alarm_EStop, "EStop", "EStop asserted. Clear and reset" },
+    { Alarm_HomingRequried, "Homing required", "Homing required. Execute homing command ($H) to continue." },
+    { Alarm_LimitsEngaged, "Limit switch engaged", "Limit switch engaged. Clear before continuing." },
+    { Alarm_ProbeProtect, "Probe protection triggered", "Probe protection triggered. Clear before continuing." },
+    { Alarm_Spindle, "Spindle at speed timeout", "Spindle at speed timeout. Clear before continuing." },
+    { Alarm_HomingFailAutoSquaringApproach, "Homing fail", "Homing fail. Could not find second limit switch for auto squared axis within search distances. Try increasing max travel, decreasing pull-off distance, or check wiring." },
+    { Alarm_SelftestFailed, "Selftest failed", "Power on selftest (POS) failed." },
+    { Alarm_MotorFault, "Motor fault", "Motor fault." }
+};
+
+static alarm_details_t details = {
+    .alarms = alarm_detail,
+    .n_alarms = sizeof(alarm_detail) / sizeof(alarm_detail_t)
+};
+
+alarm_details_t *alarms_get_details (void)
+{
+    details.on_get_alarms = grbl.on_get_alarms;
+
+    return &details;
+}
diff --git a/alarms.h b/alarms.h
index 5d10396..8ac1230 100644
--- a/alarms.h
+++ b/alarms.h
@@ -43,7 +43,8 @@ typedef enum {
     Alarm_Spindle = 14,
     Alarm_HomingFailAutoSquaringApproach = 15,
     Alarm_SelftestFailed = 16,
-    Alarm_MotorFault = 17
+    Alarm_MotorFault = 17,
+    Alarm_AlarmMax = Alarm_MotorFault
 } alarm_code_t;
 
 typedef struct {
@@ -52,25 +53,16 @@ typedef struct {
     const char *description;
 } alarm_detail_t;
 
-PROGMEM static const alarm_detail_t alarm_detail[] = {
-    { Alarm_HardLimit, "Hard limit", "Hard limit has been triggered. Machine position is likely lost due to sudden halt. Re-homing is highly recommended." },
-    { Alarm_SoftLimit, "Soft limit", "Soft limit alarm. G-code motion target exceeds machine travel. Machine position retained. Alarm may be safely unlocked." },
-    { Alarm_AbortCycle, "Abort during cycle", "Reset while in motion. Machine position is likely lost due to sudden halt. Re-homing is highly recommended." },
-    { Alarm_ProbeFailInitial, "Probe fail", "Probe fail. Probe is not in the expected initial state before starting probe cycle when G38.2 and G38.3 is not triggered and G38.4 and G38.5 is triggered." },
-    { Alarm_ProbeFailContact, "Probe fail", "Probe fail. Probe did not contact the workpiece within the programmed travel for G38.2 and G38.4." },
-    { Alarm_HomingFailReset, "Homing fail", "Homing fail. The active homing cycle was reset." },
-    { Alarm_HomingFailDoor, "Homing fail", "Homing fail. Safety door was opened during homing cycle." },
-    { Alarm_FailPulloff, "Homing fail", "Homing fail. Pull off travel failed to clear limit switch. Try increasing pull-off setting or check wiring." },
-    { Alarm_HomingFailApproach, "Homing fail", "Homing fail. Could not find limit switch within search distances. Try increasing max travel, decreasing pull-off distance, or check wiring." },
-    { Alarm_EStop, "EStop", "EStop asserted. Clear and reset" },
-    { Alarm_HomingRequried, "Homing required", "Homing required. Execute homing command ($H) to continue." },
-    { Alarm_LimitsEngaged, "Limit switch engaged", "Limit switch engaged. Clear before continuing." },
-    { Alarm_ProbeProtect, "Probe protection triggered", "Probe protection triggered. Clear before continuing." },
-    { Alarm_Spindle, "Spindle at speed timeout", "Spindle at speed timeout. Clear before continuing." },
-    { Alarm_HomingFailAutoSquaringApproach, "Homing fail", "Homing fail. Could not find second limit switch for auto squared axis within search distances. Try increasing max travel, decreasing pull-off distance, or check wiring." },
-    { Alarm_SelftestFailed, "Selftest failed", "Power on selftest (POS) failed." },
-    { Alarm_MotorFault, "Motor fault", "Motor fault." }
-};
+typedef struct alarm_details {
+    const uint16_t n_alarms;
+    const alarm_detail_t *alarms;
+    struct alarm_details *(*on_get_alarms)(void);
+} alarm_details_t;
+
+// NOTE: this must match the signature of on_get_alarms in the alarm_details_t struct above!
+typedef alarm_details_t *(*on_get_alarms_ptr)(void);
+
+alarm_details_t *alarms_get_details (void);
 
 #endif
 
diff --git a/changelog.md b/changelog.md
index 18f69ed..1f8ece3 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,17 @@
 ## grblHAL changelog
 
+Build 20210907:
+
+Core:
+* Improved HAL/core stream handling for plugin issued [realtime commands](http://svn.io-engineering.com/grblHAL/html/structgrbl__t.html#a2ff011529d0a7809a44c8609490e0306).
+* Some minor bug fixes and added rudimentary settings validations relevant when switching board map files.
+
+Drivers & plugins:
+* Fixed regression in encoder plugin.
+* Updated all drivers and relevant plugins for HAL/core API changes.
+* Added PWM inversion option to [iMXRT1062 driver](https://github.com/grblHAL/iMXRT1062).
+* Significantly improved [STM32F7xx driver](https://github.com/grblHAL/STM32F7xx), still work in progress.
+
 Build 20210819:
 
 Core:
diff --git a/config.h b/config.h
index b7f1525..c1691c1 100644
--- a/config.h
+++ b/config.h
@@ -416,19 +416,14 @@ __NOTE:__ these definitions are only referenced in this file. Do __NOT__ change!
 // #define INVERT_LIMIT_BIT_MASK (X_AXIS_BIT|Y_AXIS_BIT) // Default disabled. Uncomment to enable.
 // For inverting the probe pin use DEFAULT_INVERT_PROBE_BIT in defaults.h
 
-// Inverts the spindle enable pin from low-disabled/high-enabled to low-enabled/high-disabled. Useful
-// for some pre-built electronic boards.
-// NOTE: If VARIABLE_SPINDLE is enabled(default), this option has no effect as the PWM output and
-// spindle enable are combined to one pin. If you need both this option and spindle speed PWM,
-// uncomment the config option USE_SPINDLE_DIR_AS_ENABLE_PIN below.
+// Inverts the selected spindle output signals from active high to active low. Useful for some pre-built electronic boards.
 // #define INVERT_SPINDLE_ENABLE_PIN 1 // Default disabled. Uncomment to enable.
 // #define INVERT_SPINDLE_CCW_PIN 1    // Default disabled. Uncomment to enable. NOTE: not supported by all drivers.
 // #define INVERT_SPINDLE_PWM_PIN 1    // Default disabled. Uncomment to enable. NOTE: not supported by all drivers.
 
-// Inverts the selected coolant pin from low-disabled/high-enabled to low-enabled/high-disabled. Useful
-// for some pre-built electronic boards.
+// Inverts the selected coolant signals from active high to active low. Useful for some pre-built electronic boards.
 // #define INVERT_COOLANT_FLOOD_PIN 1 // Default disabled. Uncomment to enable.
-// #define INVERT_COOLANT_MIST_PIN 1  // Default disabled. Note: Enable M7 mist coolant in config.h
+// #define INVERT_COOLANT_MIST_PIN 1  // Default disabled. Note: not supported by all drivers.
 
 
 // Used by variable spindle output only. This forces the PWM output to a minimum duty cycle when enabled.
diff --git a/core_handlers.h b/core_handlers.h
index e0e5889..1e22ccc 100644
--- a/core_handlers.h
+++ b/core_handlers.h
@@ -27,6 +27,8 @@
 
 #include "system.h"
 #include "stream.h"
+#include "alarms.h"
+#include "errors.h"
 #include "settings.h"
 #include "report.h"
 
@@ -61,6 +63,9 @@ typedef struct {
 // Core event handler and other entry points.
 // Most of the event handlers defaults to NULL, a few is set up to call a dummy handler for simpler code.
 
+typedef bool (*enqueue_gcode_ptr)(char *data);
+typedef bool (*protocol_enqueue_realtime_command_ptr)(char c);
+
 typedef void (*on_state_change_ptr)(sys_state_t state);
 typedef void (*on_probe_completed_ptr)(void);
 typedef void (*on_program_completed_ptr)(program_flow_t program_flow, bool check_mode);
@@ -70,10 +75,9 @@ typedef bool (*on_unknown_realtime_cmd_ptr)(char c);
 typedef void (*on_report_options_ptr)(bool newopt);
 typedef void (*on_report_command_help_ptr)(void);
 typedef void (*on_global_settings_restore_ptr)(void);
-typedef setting_details_t *(*on_get_settings_ptr)(void); // NOTE: this must match the signature of the same definition in
-                                                         // the setting_details_t structure in settings.h!
 typedef void (*on_realtime_report_ptr)(stream_write_ptr stream_write, report_tracking_flags_t report);
 typedef void (*on_unknown_feedback_message_ptr)(stream_write_ptr stream_write);
+typedef void (*on_stream_changed_ptr)(stream_type_t type);
 typedef bool (*on_laser_ppi_enable_ptr)(uint_fast16_t ppi, uint_fast16_t pulse_length);
 typedef status_code_t (*on_unknown_sys_command_ptr)(sys_state_t state, char *line); // return Status_Unhandled.
 typedef status_code_t (*on_user_command_ptr)(char *line);
@@ -91,6 +95,8 @@ typedef struct {
     on_report_options_ptr on_report_options;
     on_report_command_help_ptr on_report_command_help;
     on_global_settings_restore_ptr on_global_settings_restore;
+    on_get_alarms_ptr on_get_alarms;
+    on_get_errors_ptr on_get_errors;
     on_get_settings_ptr on_get_settings;
     on_realtime_report_ptr on_realtime_report;
     on_unknown_feedback_message_ptr on_unknown_feedback_message;
@@ -98,9 +104,11 @@ typedef struct {
     on_unknown_sys_command_ptr on_unknown_sys_command; // return Status_Unhandled if not handled.
     on_get_commands_ptr on_get_commands;
     on_user_command_ptr on_user_command;
+    on_stream_changed_ptr on_stream_changed;
     on_laser_ppi_enable_ptr on_laser_ppi_enable;
     // core entry points - set up by core before driver_init() is called.
-    bool (*protocol_enqueue_gcode)(char *data);
+    enqueue_gcode_ptr enqueue_gcode;
+    enqueue_realtime_command_ptr enqueue_realtime_command;
 } grbl_t;
 
 extern grbl_t grbl;
diff --git a/errors.c b/errors.c
new file mode 100644
index 0000000..32b2b33
--- /dev/null
+++ b/errors.c
@@ -0,0 +1,97 @@
+/*
+  errors.c -
+
+  Part of grblHAL
+
+  Copyright (c) 2017-2021 Terje Io
+  Copyright (c) 2011-2016 Sungeun K. Jeon for Gnea Research LLC
+  Copyright (c) 2009-2011 Simen Svale Skogsrud
+
+  Grbl is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Grbl is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdint.h>
+
+#include "grbl.h"
+#include "core_handlers.h"
+
+PROGMEM static const status_detail_t status_detail[] = {
+    { Status_OK, "ok", NULL },
+    { Status_ExpectedCommandLetter, "Expected command letter", "G-code words consist of a letter and a value. Letter was not found." },
+    { Status_BadNumberFormat, "Bad number format", "Missing the expected G-code word value or numeric value format is not valid." },
+    { Status_InvalidStatement, "Invalid statement", "'$' system command was not recognized or supported." },
+    { Status_NegativeValue, "Value < 0", "Negative value received for an expected positive value." },
+    { Status_HomingDisabled, "Homing disabled", "Homing cycle failure. Homing is not configured via settings." },
+    { Status_SettingStepPulseMin, "Value < 2 microseconds", "Step pulse time must be greater or equal to 2 microseconds." },
+    { Status_SettingReadFail, "Settings read failed. Using defaults", "A settings read failed. Auto-restoring affected settings to default values." },
+    { Status_IdleError, "Not idle", "'$' command cannot be used unless controller state is IDLE. Ensures smooth operation during a job." },
+    { Status_SystemGClock, "G-code lock", "G-code commands are locked out during alarm or jog state." },
+    { Status_SoftLimitError, "Homing not enabled", "Soft limits cannot be enabled without homing also enabled." },
+    { Status_Overflow, "Line overflow", "Max characters per line exceeded. Received command line was not executed." },
+    { Status_MaxStepRateExceeded, "Max step rate too high", "'$' setting value cause the step rate to exceed the maximum supported." },
+    { Status_CheckDoor, "Check Door", "Safety door detected as opened and door state initiated." },
+    { Status_LineLengthExceeded, "Line length exceeded", "Build info or startup line exceeded line length limit. Line not stored." },
+    { Status_TravelExceeded, "Travel exceeded", "Jog target exceeds machine travel. Jog command has been ignored." },
+    { Status_InvalidJogCommand, "Invalid jog command", "Jog command has no '=' or contains prohibited g-code." },
+    { Status_SettingDisabledLaser, "Setting disabled", "Laser mode requires PWM output." },
+    { Status_Reset, "Reset asserted", "" },
+    { Status_NonPositiveValue, "Non positive value", "" },
+    { Status_GcodeUnsupportedCommand, "Unsupported command", "Unsupported or invalid g-code command found in block." },
+    { Status_GcodeModalGroupViolation, "Modal group violation", "More than one g-code command from same modal group found in block." },
+    { Status_GcodeUndefinedFeedRate, "Undefined feed rate", "Feed rate has not yet been set or is undefined." },
+    { Status_GcodeCommandValueNotInteger, "Invalid gcode ID:23", "G-code command in block requires an integer value." },
+    { Status_GcodeAxisCommandConflict, "Invalid gcode ID:24", "More than one g-code command that requires axis words found in block." },
+    { Status_GcodeWordRepeated, "Invalid gcode ID:25", "Repeated g-code word found in block." },
+    { Status_GcodeNoAxisWords, "Invalid gcode ID:26", "No axis words found in block for g-code command or current modal state which requires them." },
+    { Status_GcodeInvalidLineNumber, "Invalid gcode ID:27", "Line number value is invalid." },
+    { Status_GcodeValueWordMissing, "Invalid gcode ID:28", "G-code command is missing a required value word." },
+    { Status_GcodeUnsupportedCoordSys, "Invalid gcode ID:29", "G59.x work coordinate systems are not supported." },
+    { Status_GcodeG53InvalidMotionMode, "Invalid gcode ID:30", "G53 only allowed with G0 and G1 motion modes." },
+    { Status_GcodeAxisWordsExist, "Invalid gcode ID:31", "Axis words found in block when no command or current modal state uses them." },
+    { Status_GcodeNoAxisWordsInPlane, "Invalid gcode ID:32", "G2 and G3 arcs require at least one in-plane axis word." },
+    { Status_GcodeInvalidTarget, "Invalid gcode ID:33", "Motion command target is invalid." },
+    { Status_GcodeArcRadiusError, "Invalid gcode ID:34", "Arc radius value is invalid." },
+    { Status_GcodeNoOffsetsInPlane, "Invalid gcode ID:35", "G2 and G3 arcs require at least one in-plane offset word." },
+    { Status_GcodeUnusedWords, "Invalid gcode ID:36", "Unused value words found in block." },
+    { Status_GcodeG43DynamicAxisError, "Invalid gcode ID:37", "G43.1 dynamic tool length offset is not assigned to configured tool length axis." },
+    { Status_GcodeIllegalToolTableEntry, "Invalid gcode ID:38", "Tool number greater than max supported value or undefined tool selected." },
+    { Status_GcodeValueOutOfRange, "Invalid gcode ID:39", "Value out of range." },
+    { Status_GcodeToolChangePending, "Invalid gcode ID:40", "G-code command not allowed when tool change is pending." },
+    { Status_GcodeSpindleNotRunning, "Invalid gcode ID:41", "Spindle not running when motion commanded in CSS or spindle sync mode." },
+    { Status_GcodeIllegalPlane, "Invalid gcode ID:42", "Plane must be ZX for threading." },
+    { Status_GcodeMaxFeedRateExceeded, "Invalid gcode ID:43", "Max. feed rate exceeded." },
+    { Status_GcodeRPMOutOfRange, "Invalid gcode ID:44", "RPM out of range." },
+    { Status_LimitsEngaged, "Limit switch engaged", "Only homing is allowed when a limit switch is engaged." },
+    { Status_HomingRequired, "Homing required", "Home machine to continue." },
+    { Status_GCodeToolError, "Invalid gcode ID:47", "ATC: current tool is not set. Set current tool with M61." },
+    { Status_ValueWordConflict, "Invalid gcode ID:48", "Value word conflict." },
+    { Status_SelfTestFailed, "Self test failed", "Power on self test failed. A hard reset is required." },
+    { Status_EStop, "E-stop", "Emergency stop active." },
+    { Status_MotorFault, "Motor fault", "Motor fault." },
+    { Status_SettingValueOutOfRange, "Value out of range.", "Setting value is out of range." },
+    { Status_SettingDisabled, "Setting disabled", "Setting is not available, possibly due to limited driver support." },
+    { Status_GcodeInvalidRetractPosition, "Invalid gcode ID:54", "Retract position is less than drill depth." }
+ };
+
+static error_details_t details = {
+    .errors = status_detail,
+    .n_errors = sizeof(status_detail) / sizeof(status_detail_t)
+};
+
+error_details_t *errors_get_details (void)
+{
+    details.on_get_errors = grbl.on_get_errors;
+
+    return &details;
+}
diff --git a/errors.h b/errors.h
index ea7bcb4..79b6543 100644
--- a/errors.h
+++ b/errors.h
@@ -93,7 +93,8 @@ typedef enum {
     Status_SDFileEmpty = 64,
 
     Status_BTInitError = 70,
-    Status_Unhandled // For internal use only
+    Status_Unhandled, // For internal use only
+    Status_StatusMax = Status_Unhandled
 } status_code_t;
 
 typedef struct {
@@ -102,68 +103,15 @@ typedef struct {
     const char *description;
 } status_detail_t;
 
-PROGMEM static const status_detail_t status_detail[] = {
-    { Status_OK, "ok", NULL },
-    { Status_ExpectedCommandLetter, "Expected command letter", "G-code words consist of a letter and a value. Letter was not found." },
-    { Status_BadNumberFormat, "Bad number format", "Missing the expected G-code word value or numeric value format is not valid." },
-    { Status_InvalidStatement, "Invalid statement", "Grbl '$' system command was not recognized or supported." },
-    { Status_NegativeValue, "Value < 0", "Negative value received for an expected positive value." },
-    { Status_HomingDisabled, "Homing disabled", "Homing cycle failure. Homing is not configured via settings." },
-    { Status_SettingStepPulseMin, "Value < 2 microseconds", "Step pulse time must be greater or equal to 2 microseconds." },
-    { Status_SettingReadFail, "EEPROM read fail. Using defaults", "An EEPROM read failed. Auto-restoring affected EEPROM to default values." },
-    { Status_IdleError, "Not idle", "Grbl '$' command cannot be used unless Grbl is IDLE. Ensures smooth operation during a job." },
-    { Status_SystemGClock, "G-code lock", "G-code commands are locked out during alarm or jog state." },
-    { Status_SoftLimitError, "Homing not enabled", "Soft limits cannot be enabled without homing also enabled." },
-    { Status_Overflow, "Line overflow", "Max characters per line exceeded. Received command line was not executed." },
-    { Status_MaxStepRateExceeded, "Step rate > 30kHz", "Grbl '$' setting value cause the step rate to exceed the maximum supported." },
-    { Status_CheckDoor, "Check Door", "Safety door detected as opened and door state initiated." },
-    { Status_LineLengthExceeded, "Line length exceeded", "Build info or startup line exceeded EEPROM line length limit. Line not stored." },
-    { Status_TravelExceeded, "Travel exceeded", "Jog target exceeds machine travel. Jog command has been ignored." },
-    { Status_InvalidJogCommand, "Invalid jog command", "Jog command has no '=' or contains prohibited g-code." },
-    { Status_SettingDisabledLaser, "Setting disabled", "Laser mode requires PWM output." },
-    { Status_Reset, "Reset asserted", "" },
-    { Status_NonPositiveValue, "Non positive value", "" },
-    { Status_GcodeUnsupportedCommand, "Unsupported command", "Unsupported or invalid g-code command found in block." },
-    { Status_GcodeModalGroupViolation, "Modal group violation", "More than one g-code command from same modal group found in block." },
-    { Status_GcodeUndefinedFeedRate, "Undefined feed rate", "Feed rate has not yet been set or is undefined." },
-    { Status_GcodeCommandValueNotInteger, "Invalid gcode ID:23", "G-code command in block requires an integer value." },
-    { Status_GcodeAxisCommandConflict, "Invalid gcode ID:24", "More than one g-code command that requires axis words found in block." },
-    { Status_GcodeWordRepeated, "Invalid gcode ID:25", "Repeated g-code word found in block." },
-    { Status_GcodeNoAxisWords, "Invalid gcode ID:26", "No axis words found in block for g-code command or current modal state which requires them." },
-    { Status_GcodeInvalidLineNumber, "Invalid gcode ID:27", "Line number value is invalid." },
-    { Status_GcodeValueWordMissing, "Invalid gcode ID:28", "G-code command is missing a required value word." },
-    { Status_GcodeUnsupportedCoordSys, "Invalid gcode ID:29", "G59.x work coordinate systems are not supported." },
-    { Status_GcodeG53InvalidMotionMode, "Invalid gcode ID:30", "G53 only allowed with G0 and G1 motion modes." },
-    { Status_GcodeAxisWordsExist, "Invalid gcode ID:31", "Axis words found in block when no command or current modal state uses them." },
-    { Status_GcodeNoAxisWordsInPlane, "Invalid gcode ID:32", "G2 and G3 arcs require at least one in-plane axis word." },
-    { Status_GcodeInvalidTarget, "Invalid gcode ID:33", "Motion command target is invalid." },
-    { Status_GcodeArcRadiusError, "Invalid gcode ID:34", "Arc radius value is invalid." },
-    { Status_GcodeNoOffsetsInPlane, "Invalid gcode ID:35", "G2 and G3 arcs require at least one in-plane offset word." },
-    { Status_GcodeUnusedWords, "Invalid gcode ID:36", "Unused value words found in block." },
-    { Status_GcodeG43DynamicAxisError, "Invalid gcode ID:37", "G43.1 dynamic tool length offset is not assigned to configured tool length axis." },
-    { Status_GcodeIllegalToolTableEntry, "Invalid gcode ID:38", "Tool number greater than max supported value or undefined tool selected." },
-    { Status_GcodeValueOutOfRange, "Invalid gcode ID:39", "Value out of range." },
-    { Status_GcodeToolChangePending, "Invalid gcode ID:40", "G-code command not allowed when tool change is pending." },
-    { Status_GcodeSpindleNotRunning, "Invalid gcode ID:41", "Spindle not running when motion commanded in CSS or spindle sync mode." },
-    { Status_GcodeIllegalPlane, "Invalid gcode ID:42", "Plane must be ZX for threading." },
-    { Status_GcodeMaxFeedRateExceeded, "Invalid gcode ID:43", "Max. feed rate exceeded." },
-    { Status_GcodeRPMOutOfRange, "Invalid gcode ID:44", "RPM out of range." },
-    { Status_LimitsEngaged, "Limit switch engaged", "Only homing is allowed when a limit switch is engaged." },
-    { Status_HomingRequired, "Homing required", "Home machine to continue." },
-    { Status_GCodeToolError, "Invalid gcode ID:47", "ATC: current tool is not set. Set current tool with M61." },
-    { Status_ValueWordConflict, "Invalid gcode ID:48", "Value word conflict." },
-    { Status_SelfTestFailed, "Self test failed", "Power on self test failed. A hard reset is required." },
-    { Status_EStop, "E-stop", "Emergency stop active." },
-    { Status_MotorFault, "Motor fault", "Motor fault." },
-    { Status_SettingValueOutOfRange, "Value out of range.", "Setting value is out of range." },
-    { Status_SettingDisabled, "Setting disabled", "Setting is not available, possibly due to limited driver support." },
-    { Status_GcodeInvalidRetractPosition, "Invalid gcode ID:54", "Retract position is less than drill depth." },
-    { Status_SDMountError, "SD Card", "SD Card mount failed." },
-    { Status_SDReadError, "SD Card", "SD Card file open/read failed." },
-    { Status_SDFailedOpenDir, "SD Card", "SD Card directory listing failed." },
-    { Status_SDDirNotFound, "SD Card", "SD Card directory not found." },
-    { Status_SDFileEmpty, "SD Card", "SD Card file empty." },
-    { Status_BTInitError, "Bluetooth", "Bluetooth initalisation failed." }
-};
+typedef struct error_details {
+    const uint16_t n_errors;
+    const status_detail_t *errors;
+    struct error_details *(*on_get_errors)(void);
+} error_details_t;
+
+// NOTE: this must match the signature of on_get_alarms in the on_get_statuses struct above!
+typedef error_details_t *(*on_get_errors_ptr)(void);
+
+error_details_t *errors_get_details (void);
 
 #endif
diff --git a/grbl.h b/grbl.h
index 1d4ab83..be581b7 100644
--- a/grbl.h
+++ b/grbl.h
@@ -34,7 +34,7 @@
 #else
 #define GRBL_VERSION "1.1f"
 #endif
-#define GRBL_VERSION_BUILD "20210819"
+#define GRBL_VERSION_BUILD "20210907"
 
 // The following symbols are set here if not already set by the compiler or in config.h
 // Do NOT change here!
diff --git a/grbllib.c b/grbllib.c
index 9765f06..565acb6 100644
--- a/grbllib.c
+++ b/grbllib.c
@@ -103,7 +103,8 @@ int grbl_enter (void)
     // Clear all and set some core function pointers
     memset(&grbl, 0, sizeof(grbl_t));
     grbl.on_execute_realtime = protocol_execute_noop;
-    grbl.protocol_enqueue_gcode = protocol_enqueue_gcode;
+    grbl.enqueue_gcode = protocol_enqueue_gcode;
+    grbl.enqueue_realtime_command = stream_enqueue_realtime_command;
     grbl.on_report_options = dummy_bool_handler;
 
     // Clear all and set some HAL function pointers
@@ -181,7 +182,7 @@ int grbl_enter (void)
 #endif
 
 #ifdef SPINDLE_PWM_DIRECT
-    driver_ok = driver_ok && hal.spindle.get_pwm != NULL && hal.spindle.update_pwm != NULL;
+    driver_ok = driver_ok && (!hal.driver_cap.variable_spindle || (hal.spindle.get_pwm != NULL && hal.spindle.update_pwm != NULL));
 #endif
 
     if(!driver_ok) {
diff --git a/nvs_buffer.c b/nvs_buffer.c
index 74faa6d..87f0fc6 100644
--- a/nvs_buffer.c
+++ b/nvs_buffer.c
@@ -68,7 +68,7 @@ static const emap_t target[] = {
     {TOOL_ADDR(5), NVS_GROUP_TOOLS, 5},
     {TOOL_ADDR(6), NVS_GROUP_TOOLS, 6},
     {TOOL_ADDR(7), NVS_GROUP_TOOLS, 7},
-#if N_TOOL > 8
+#if N_TOOLS > 8
 #error Increase number of tool entries!
 #endif
 #endif
@@ -373,6 +373,14 @@ void nvs_memmap (void)
     strcat(buf, uitoa(sizeof(settings_t) + NVS_CRC_BYTES));
     report_message(buf, Message_Plain);
 
+#ifdef N_TOOLS
+    strcpy(buf, "Tool table: ");
+    strcat(buf, uitoa(NVS_ADDR_TOOL_TABLE));
+    strcat(buf, " ");
+    strcat(buf, uitoa(N_TOOLS * (sizeof(tool_data_t) + NVS_CRC_BYTES)));
+    report_message(buf, Message_Plain);
+#endif
+
     strcpy(buf, "Parameters: ");
     strcat(buf, uitoa(NVS_ADDR_PARAMETERS));
     strcat(buf, " ");
diff --git a/planner.c b/planner.c
index b3bd33d..9ba9ecd 100644
--- a/planner.c
+++ b/planner.c
@@ -315,7 +315,7 @@ inline static float plan_compute_profile_parameters (plan_block_t *block, float
 }
 
 // Re-calculates buffered motions profile parameters upon a motion-based override change.
-void plan_update_velocity_profile_parameters ()
+static void plan_update_velocity_profile_parameters ()
 {
     plan_block_t *block = block_buffer_tail;
     float prev_nominal_speed = SOME_LARGE_VALUE; // Set high for first block nominal speed calculation.
diff --git a/planner.h b/planner.h
index c7a1776..2eaceb2 100644
--- a/planner.h
+++ b/planner.h
@@ -132,9 +132,6 @@ float plan_get_exec_block_exit_speed_sqr();
 // Called by main program during planner calculations and step segment buffer during initialization.
 float plan_compute_profile_nominal_speed(plan_block_t *block);
 
-// Re-calculates buffered motions profile parameters upon a motion-based override change.
-void plan_update_velocity_profile_parameters();
-
 // Reset the planner position vector (in steps)
 void plan_sync_position();
 
@@ -147,7 +144,6 @@ uint_fast16_t plan_get_block_buffer_available();
 // Returns the status of the block ring buffer. True, if buffer is full.
 bool plan_check_full_buffer();
 
-void plan_get_planner_mpos(float *target);
 void plan_feed_override (uint_fast8_t feed_override, uint_fast8_t rapid_override);
 
 #endif
diff --git a/plugins_init.h b/plugins_init.h
index 3be81c5..bca7c28 100644
--- a/plugins_init.h
+++ b/plugins_init.h
@@ -48,6 +48,11 @@
     openpnp_init();
 #endif
 
+#if WEBUI_ENABLE
+    extern void webui_init (void);
+    webui_init();
+#endif
+
     my_plugin_init();
 
 #if ODOMETER_ENABLE
diff --git a/report.c b/report.c
index f02dac2..7f6024d 100644
--- a/report.c
+++ b/report.c
@@ -1381,6 +1381,15 @@ static void report_bitfield (const char *format, bool bitmap)
     }
 }
 
+static void write_quoted (const char *s, const char *sep)
+{
+    hal.stream.write("\"");
+    hal.stream.write(s); // TODO: escape double quoutes
+    hal.stream.write("\"");
+    if(sep)
+        hal.stream.write(sep);
+}
+
 static void report_settings_detail (settings_format_t format, const setting_detail_t *setting, uint_fast8_t offset)
 {
     switch(format)
@@ -1474,126 +1483,130 @@ static void report_settings_detail (settings_format_t format, const setting_deta
             break;
 
         case SettingsFormat_Grbl:
-            hal.stream.write("\"");
-            hal.stream.write(uitoa(setting->id + offset));
-            hal.stream.write("\",\"");
-            if(setting->group == Group_Axis0)
-                hal.stream.write(axis_letter[offset]);
-            hal.stream.write(setting->name[0] == '?' ? &setting->name[1] : setting->name); // temporary hack for ? prefix...
-            if(setting->unit) {
-                hal.stream.write("\",\"");
-                hal.stream.write(setting->unit);
-            } else // TODO: output sensible unit from datatype
-                hal.stream.write("\",\"");
-#ifndef NO_SETTINGS_DESCRIPTIONS
-            hal.stream.write("\",\"");
-            report_setting_description(format, (setting_id_t)(setting->id + offset));
-            hal.stream.write("\"");
-#else
-            hal.stream.write("\",\"\"");
-#endif
+            {
+                write_quoted(uitoa(setting->id + offset), ",");
+                hal.stream.write("\"");
+                if(setting->group == Group_Axis0)
+                    hal.stream.write(axis_letter[offset]);
+                hal.stream.write(setting->name[0] == '?' ? &setting->name[1] : setting->name); // temporary hack for ? prefix...
+                hal.stream.write("\",");
+                if(setting->unit) {
+                    write_quoted(setting->unit, ",");
+                } else // TODO: output sensible unit from datatype
+                    write_quoted("", ",");
+
+    #ifndef NO_SETTINGS_DESCRIPTIONS
+                const char *description = setting_get_description((setting_id_t)(setting->id + offset));
+                write_quoted(description ? description : "", ",");
+    #else
+                write_quoted("", NULL);
+    #endif
+            }
             break;
 
         case SettingsFormat_grblHAL:
-            hal.stream.write(uitoa(setting->id + offset));
+            {
+                hal.stream.write(uitoa(setting->id + offset));
 
-            hal.stream.write("\t");
+                hal.stream.write("\t");
 
-            if(setting->group == Group_Axis0)
-                hal.stream.write(axis_letter[offset]);
-            hal.stream.write(setting->name[0] == '?' ? &setting->name[1] : setting->name); // temporary hack for ? prefix...
+                if(setting->group == Group_Axis0)
+                    hal.stream.write(axis_letter[offset]);
+                hal.stream.write(setting->name[0] == '?' ? &setting->name[1] : setting->name); // temporary hack for ? prefix...
 
-            hal.stream.write("\t");
+                hal.stream.write("\t");
 
-            if(setting->unit)
-                hal.stream.write(setting->unit);
-            else if(setting->datatype == Format_AxisMask || setting->datatype == Format_Bitfield || setting->datatype == Format_XBitfield)
-                hal.stream.write("mask");
-            else if(setting->datatype == Format_Bool)
-                hal.stream.write("boolean");
-            else if(setting->datatype == Format_RadioButtons)
-                hal.stream.write("integer");
-
-            hal.stream.write("\t");
-/*
-            Format_Bool = 0,
-            Format_Bitfield,
-            Format_XBitfield,
-            Format_RadioButtons,
-            Format_AxisMask,
-            Format_Integer, // 32 bit
-            ,
-            Format_String,
-            Format_Password,
-            Format_IPv4,
-            // For internal use only
-            Format_Int8,
-            Format_Int16,
-*/
-            switch(setting_datatype_to_external(setting->datatype)) {
-
-                case Format_Integer:
+                if(setting->unit)
+                    hal.stream.write(setting->unit);
+                else if(setting->datatype == Format_AxisMask || setting->datatype == Format_Bitfield || setting->datatype == Format_XBitfield)
+                    hal.stream.write("mask");
+                else if(setting->datatype == Format_Bool)
+                    hal.stream.write("boolean");
+                else if(setting->datatype == Format_RadioButtons)
                     hal.stream.write("integer");
-                    break;
 
-                case Format_Decimal:
-                    hal.stream.write("float");
-                    break;
+                hal.stream.write("\t");
+    /*
+                Format_Bool = 0,
+                Format_Bitfield,
+                Format_XBitfield,
+                Format_RadioButtons,
+                Format_AxisMask,
+                Format_Integer, // 32 bit
+                ,
+                Format_String,
+                Format_Password,
+                Format_IPv4,
+                // For internal use only
+                Format_Int8,
+                Format_Int16,
+    */
+                switch(setting_datatype_to_external(setting->datatype)) {
 
-                case Format_Bool:
-                    hal.stream.write("bool");
-                    break;
+                    case Format_Integer:
+                        hal.stream.write("integer");
+                        break;
 
-                case Format_AxisMask:
-                case Format_Bitfield:
-                    hal.stream.write("bitfield");
-                    break;
+                    case Format_Decimal:
+                        hal.stream.write("float");
+                        break;
 
-                case Format_XBitfield:
-                    hal.stream.write("xbitfield");
-                    break;
+                    case Format_Bool:
+                        hal.stream.write("bool");
+                        break;
 
-                case Format_RadioButtons:
-                    hal.stream.write("radiobuttons");
-                    break;
+                    case Format_AxisMask:
+                    case Format_Bitfield:
+                        hal.stream.write("bitfield");
+                        break;
 
-                case Format_IPv4:
-                    hal.stream.write("ipv4");
-                    break;
+                    case Format_XBitfield:
+                        hal.stream.write("xbitfield");
+                        break;
 
-                case Format_String:
-                    hal.stream.write("string");
-                    break;
+                    case Format_RadioButtons:
+                        hal.stream.write("radiobuttons");
+                        break;
 
-                case Format_Password:
-                    hal.stream.write("password");
-                    break;
+                    case Format_IPv4:
+                        hal.stream.write("ipv4");
+                        break;
 
-                default:
-                    break;
+                    case Format_String:
+                        hal.stream.write("string");
+                        break;
+
+                    case Format_Password:
+                        hal.stream.write("password");
+                        break;
+
+                    default:
+                        break;
+                }
+
+                hal.stream.write("\t");
+
+                if(setting->format)
+                    hal.stream.write(setting->format);
+                else if (setting->datatype == Format_AxisMask)
+                    hal.stream.write("axes");
+
+                hal.stream.write("\t");
+
+    #ifndef NO_SETTINGS_DESCRIPTIONS
+                const char *description = setting_get_description((setting_id_t)(setting->id + offset));
+                hal.stream.write(description ? description : "");
+    #endif
+                hal.stream.write("\t");
+
+                if(setting->min_value)
+                    hal.stream.write(setting->min_value);
+
+                hal.stream.write("\t");
+
+                if(setting->max_value)
+                    hal.stream.write(setting->max_value);
             }
-
-            hal.stream.write("\t");
-
-            if(setting->format)
-                hal.stream.write(setting->format);
-            else if (setting->datatype == Format_AxisMask)
-                hal.stream.write("axes");
-
-            hal.stream.write("\t");
-
-#ifndef NO_SETTINGS_DESCRIPTIONS
-            report_setting_description(format, (setting_id_t)(setting->id + offset));
-#endif
-            hal.stream.write("\t");
-
-            if(setting->min_value)
-                hal.stream.write(setting->min_value);
-
-            hal.stream.write("\t");
-
-            if(setting->max_value)
-                hal.stream.write(setting->max_value);
             break;
     }
 
@@ -1746,21 +1759,7 @@ status_code_t report_settings_details (settings_format_t format, setting_id_t id
 
 status_code_t report_setting_description (settings_format_t format, setting_id_t id)
 {
-    uint_fast16_t idx;
-    const char *description = NULL;
-    setting_details_t *settings = settings_get_details();
-    const setting_detail_t *setting = setting_get_details(id, NULL);
-
-    if(setting) do {
-        if(settings->descriptions) {
-            idx = settings->n_descriptions;
-            do {
-                if(settings->descriptions[--idx].id == setting->id)
-                    description = settings->descriptions[idx].description;
-            } while(idx && description == NULL);
-        }
-        settings = settings->on_get_settings ? settings->on_get_settings() : NULL;
-    } while(settings && description == NULL);
+    const char *description = setting_get_description(id);
 
     if(format == SettingsFormat_MachineReadable) {
         hal.stream.write("[SETTINGDESCR:");
@@ -1778,42 +1777,74 @@ status_code_t report_setting_description (settings_format_t format, setting_id_t
 
 #endif
 
-status_code_t report_alarm_details (void)
+status_code_t report_alarm_details (bool grbl_format)
 {
-    uint_fast16_t idx, n_alarms = sizeof(alarm_detail) / sizeof(alarm_detail_t);
+    uint_fast16_t idx;
+    alarm_details_t *list = alarms_get_details();
 
-    for(idx = 0; idx < n_alarms; idx++) {
+    if(grbl_format)
+        hal.stream.write("\"Alarm Code in v1.1+\",\" Alarm Message in v1.0-\",\" Alarm Description\"" ASCII_EOL);
 
-        hal.stream.write("[ALARMCODE:");
+    do { // TODO: add sorting?
 
-        hal.stream.write(uitoa(alarm_detail[idx].id));
-        hal.stream.write(vbar);
-        hal.stream.write(alarm_detail[idx].name);
-        hal.stream.write(vbar);
-        if(alarm_detail[idx].description)
-            hal.stream.write(alarm_detail[idx].description);
-        hal.stream.write("]" ASCII_EOL);
-    }
+        for(idx = 0; idx < list->n_alarms; idx++) {
+
+            if(grbl_format) {
+                write_quoted(uitoa(list->alarms[idx].id), ",");
+                write_quoted(list->alarms[idx].name, ",");
+                write_quoted(list->alarms[idx].description ? list->alarms[idx].description : "", NULL);
+                hal.stream.write(ASCII_EOL);
+            } else {
+                hal.stream.write("[ALARMCODE:");
+                hal.stream.write(uitoa(list->alarms[idx].id));
+                hal.stream.write(vbar);
+                hal.stream.write(list->alarms[idx].name);
+                hal.stream.write(vbar);
+                if(list->alarms[idx].description)
+                    hal.stream.write(list->alarms[idx].description);
+                hal.stream.write("]" ASCII_EOL);
+            }
+        }
+
+        list = list->on_get_alarms ? list->on_get_alarms() : NULL;
+
+    } while(list);
 
     return Status_OK;
 }
 
-status_code_t report_error_details (void)
+status_code_t report_error_details (bool grbl_format)
 {
-    uint_fast16_t idx, n_alarms = sizeof(status_detail) / sizeof(status_detail_t);
+    uint_fast16_t idx;
+    error_details_t *list = errors_get_details();
 
-    for(idx = 0; idx < n_alarms; idx++) {
+    if(grbl_format)
+        hal.stream.write("\"Error Code in v1.1+\",\"Error Message in v1.0-\",\"Error Description\"" ASCII_EOL);
 
-        hal.stream.write("[ERRORCODE:");
+    do { // TODO: add sorting?
 
-        hal.stream.write(uitoa(status_detail[idx].id));
-        hal.stream.write(vbar);
-        hal.stream.write(status_detail[idx].name);
-        hal.stream.write(vbar);
-        if(status_detail[idx].description)
-            hal.stream.write(status_detail[idx].description);
-        hal.stream.write("]" ASCII_EOL);
-    }
+        for(idx = 0; idx < list->n_errors; idx++) {
+
+            if(grbl_format) {
+                write_quoted(uitoa(list->errors[idx].id), ",");
+                write_quoted(list->errors[idx].name, ",");
+                write_quoted(list->errors[idx].description ? list->errors[idx].description : "", NULL);
+                hal.stream.write(ASCII_EOL);
+            } else {
+                hal.stream.write("[ERRORCODE:");
+                hal.stream.write(uitoa(list->errors[idx].id));
+                hal.stream.write(vbar);
+                hal.stream.write(list->errors[idx].name);
+                hal.stream.write(vbar);
+                if(list->errors[idx].description)
+                    hal.stream.write(list->errors[idx].description);
+                hal.stream.write("]" ASCII_EOL);
+            }
+        }
+
+        list = list->on_get_errors ? list->on_get_errors() : NULL;
+
+    } while(list);
 
     return Status_OK;
 }
@@ -1943,7 +1974,6 @@ status_code_t report_current_limit_state (sys_state_t state, char *args)
     return Status_OK;
 }
 
-
 // Prints spindle data (encoder pulse and index count, angular position).
 status_code_t report_spindle_data (sys_state_t state, char *args)
 {
diff --git a/report.h b/report.h
index 4025718..7a6fc39 100644
--- a/report.h
+++ b/report.h
@@ -93,8 +93,8 @@ void report_execute_startup_message (char *line, status_code_t status_code);
 // Prints build info and user info.
 void report_build_info (char *line, bool extended);
 
-status_code_t report_alarm_details (void);
-status_code_t report_error_details (void);
+status_code_t report_alarm_details (bool grbl_format);
+status_code_t report_error_details (bool grbl_format);
 status_code_t report_setting_group_details (bool by_id, char *prefix);
 status_code_t report_settings_details (settings_format_t format, setting_id_t setting, setting_group_t group);
 #ifndef NO_SETTINGS_DESCRIPTIONS
diff --git a/settings.c b/settings.c
index c328a5f..29d7671 100644
--- a/settings.c
+++ b/settings.c
@@ -1465,17 +1465,21 @@ bool settings_read_tool_data (uint32_t tool, tool_data_t *tool_data)
 #endif
 }
 
-// Read Grbl global settings from persistent storage.
+// Read global settings from persistent storage.
 // Checks version-byte of non-volatile storage and global settings copy.
 bool read_global_settings ()
 {
     bool ok = hal.nvs.type != NVS_None && SETTINGS_VERSION == hal.nvs.get_byte(0) && hal.nvs.memcpy_from_nvs((uint8_t *)&settings, NVS_ADDR_GLOBAL, sizeof(settings_t), true) == NVS_TransferResult_OK;
 
+    // Sanity check of settings, board map could have been changed...
+    if(settings.mode == Mode_Laser && !hal.driver_cap.variable_spindle)
+        settings.mode = Mode_Standard;
+
     return ok && settings.version == SETTINGS_VERSION;
 }
 
 
-// Write Grbl global settings to persistent storage
+// Write global settings to persistent storage
 void settings_write_global (void)
 {
     if(override_backup.valid)
@@ -1486,7 +1490,7 @@ void settings_write_global (void)
 }
 
 
-// Restore Grbl global settings to defaults and write to persistent storage
+// Restore global settings to defaults and write to persistent storage
 void settings_restore (settings_restore_t restore)
 {
     uint_fast8_t idx;
@@ -1728,6 +1732,32 @@ const setting_detail_t *setting_get_details (setting_id_t id, setting_details_t
     return NULL;
 }
 
+const char *setting_get_description (setting_id_t id)
+{
+    const char *description = NULL;
+
+#ifndef NO_SETTINGS_DESCRIPTIONS
+
+    uint_fast16_t idx;
+    setting_details_t *settings = settings_get_details();
+    const setting_detail_t *setting = setting_get_details(id, NULL);
+
+    if(setting) do {
+        if(settings->descriptions) {
+            idx = settings->n_descriptions;
+            do {
+                if(settings->descriptions[--idx].id == setting->id)
+                    description = settings->descriptions[idx].description;
+            } while(idx && description == NULL);
+        }
+        settings = settings->on_get_settings ? settings->on_get_settings() : NULL;
+    } while(settings && description == NULL);
+
+#endif
+
+    return description;
+}
+
 static status_code_t validate_value (const setting_detail_t *setting, float value)
 {
     float val;
diff --git a/settings.h b/settings.h
index 98fd5f3..7d866eb 100644
--- a/settings.h
+++ b/settings.h
@@ -704,6 +704,9 @@ typedef struct setting_details {
     driver_settings_restore_ptr restore;
 } setting_details_t;
 
+// NOTE: this must match the signature of on_get_settings in the setting_details_t structure above!
+typedef setting_details_t *(*on_get_settings_ptr)(void);
+
 extern settings_t settings;
 
 // Initialize the configuration subsystem (load settings from persistent storage)
@@ -749,6 +752,7 @@ setting_details_t *settings_get_details (void);
 bool settings_is_group_available (setting_group_t group);
 bool settings_iterator (const setting_detail_t *setting, setting_output_ptr callback, void *data);
 const setting_detail_t *setting_get_details (setting_id_t id, setting_details_t **set);
+const char *setting_get_description (setting_id_t id);
 setting_datatype_t setting_datatype_to_external (setting_datatype_t datatype);
 setting_group_t settings_normalize_group (setting_group_t group);
 char *setting_get_value (const setting_detail_t *setting, uint_fast16_t offset);
diff --git a/stepper.c b/stepper.c
index 67b02e0..bd3cee4 100644
--- a/stepper.c
+++ b/stepper.c
@@ -550,15 +550,16 @@ void st_reset ()
     // NOTE: buffer indices starts from 1 for simpler driver coding!
 
     // Set up stepper block ringbuffer as circular linked list and add id
-    uint_fast8_t idx;
-    for(idx = 0 ; idx <= SEGMENT_BUFFER_SIZE - 2 ; idx++) {
-        st_block_buffer[idx].next = &st_block_buffer[idx == SEGMENT_BUFFER_SIZE - 2 ? 0 : idx + 1];
+    uint_fast8_t idx, idx_max = (sizeof(st_block_buffer) / sizeof(st_block_t)) - 1;
+    for(idx = 0 ; idx <= idx_max ; idx++) {
+        st_block_buffer[idx].next = &st_block_buffer[idx == idx_max ? 0 : idx + 1];
         st_block_buffer[idx].id = idx + 1;
     }
 
     // Set up segments ringbuffer as circular linked list, add id and clear AMASS level
-    for(idx = 0 ; idx <= SEGMENT_BUFFER_SIZE - 1 ; idx++) {
-        segment_buffer[idx].next = &segment_buffer[idx == SEGMENT_BUFFER_SIZE - 1 ? 0 : idx + 1];
+    idx_max = (sizeof(segment_buffer) / sizeof(segment_t)) - 1;
+    for(idx = 0 ; idx <= idx_max ; idx++) {
+        segment_buffer[idx].next = &segment_buffer[idx == idx_max ? 0 : idx + 1];
         segment_buffer[idx].id = idx + 1;
         segment_buffer[idx].amass_level = 0;
     }
diff --git a/stream.c b/stream.c
index 5996518..12405c7 100644
--- a/stream.c
+++ b/stream.c
@@ -91,6 +91,11 @@ ISR_CODE bool stream_buffer_all (char c)
     return false;
 }
 
+ISR_CODE bool stream_enqueue_realtime_command (char c)
+{
+    return hal.stream.enqueue_rt_command ? hal.stream.enqueue_rt_command(c) : protocol_enqueue_realtime_command(c);
+}
+
 ISR_CODE bool stream_enable_mpg (const io_stream_t *mpg_stream, bool mpg_mode)
 {
     static io_stream_t org_stream = {
@@ -138,12 +143,14 @@ ISR_CODE bool stream_enable_mpg (const io_stream_t *mpg_stream, bool mpg_mode)
 
 #ifdef DEBUGOUT
 
-static stream_write_ptr dbg_write;
+static stream_write_ptr dbg_write = NULL;
 
-static void debug_write (const char *s)
+void debug_write (const char *s)
 {
-    dbg_write(s);
-    while(hal.debug.get_tx_buffer_count()); // Wait until message is delivered
+    if(dbg_write) {
+        dbg_write(s);
+        while(hal.debug.get_tx_buffer_count()); // Wait until message is delivered
+    }
 }
 
 void debug_stream_init (io_stream_t *stream)
diff --git a/stream.h b/stream.h
index 6332e0a..367abf3 100644
--- a/stream.h
+++ b/stream.h
@@ -56,7 +56,7 @@ Helper functions for saving away and restoring a stream input buffer. _Not refer
 #endif
 
 #ifndef BLOCK_TX_BUFFER_SIZE
-#define BLOCK_TX_BUFFER_SIZE 256
+#define BLOCK_TX_BUFFER_SIZE 1024
 #endif
 
 // Serial baud rate
@@ -124,11 +124,23 @@ This should be called by driver code prior to inserting a character into the inp
 */
 typedef bool (*enqueue_realtime_command_ptr)(char c);
 
+
+/*! \brief Optional, but recommended, pointer to function for enqueueing realtime command characters.
+\param c character to enqueue.
+\returns \a true if sucessfully enqueued, \a false otherwise.
+
+__NOTE:__ Stream implementations should pass the character over the current handler registered by the set_enqueue_rt_handler().
+
+User or plugin code should __not__ enqueue realtime command characters via this handler, it should call \a grbl.enqueue_realtime_command() instead.
+*/
+typedef bool (*enqueue_realtime_command2_ptr)(char c);
+
+
 /*! \brief Pointer to function for setting the enqueue realtime commands handler.
 \param enqueue_realtime_command_ptr pointer to the new handler function.
 \returns \a enqueue_realtime_command_ptr pointer to the replaced function.
 
-__NOTE:__ Stream implementation should hold a pointer to the handler in a local variable and typically
+__NOTE:__ Stream implementations should hold a pointer to the handler in a local variable and typically
 set it to protocol_enqueue_realtime_command() on initialization.
 */
 typedef enqueue_realtime_command_ptr (*set_enqueue_rt_handler_ptr)(enqueue_realtime_command_ptr);
@@ -179,7 +191,6 @@ for handing feed-holds, overrides, soft resets etc.
 
 \param disable \a true to disable stream, \a false to enable,
 */
-
 typedef bool (*disable_stream_ptr)(bool disable);
 
 //! Properties and handlers for stream I/O
@@ -190,10 +201,11 @@ typedef struct {
     stream_write_ptr write;                                 //!< Handler for writing string to current output stream only.
     stream_write_ptr write_all;                             //!< Handler for writing string to all active output streams.
     stream_write_char_ptr write_char;                       //!< Handler for writing a single character to current stream only.
+    enqueue_realtime_command2_ptr enqueue_rt_command;       //!< (Optional) handler for enqueueing a realtime command character.
     stream_read_ptr read;                                   //!< Handler for reading a single character from the input stream.
     flush_stream_buffer_ptr reset_read_buffer;              //!< Handler for flushing the input buffer.
     cancel_read_buffer_ptr cancel_read_buffer;              //!< Handler for flushing the input buffer and inserting an #ASCII_CAN character.
-    set_enqueue_rt_handler_ptr set_enqueue_rt_handler;      //!< Handler for setting the enqueue realtime commands handler.
+    set_enqueue_rt_handler_ptr set_enqueue_rt_handler;      //!< Handler for setting the enqueue realtime command character handler.
     suspend_read_ptr suspend_read;                          //!< Optional handler for saving away and restoring the current input buffer.
     stream_write_n_ptr write_n;                             //!< Optional handler for writing n characters to current output stream only. Required for Modbus support.
     disable_stream_ptr disable;                             //!< Optional handler for disabling/enabling a stream. Recommended?
@@ -257,7 +269,10 @@ bool stream_buffer_all (char c);
 
 bool stream_tx_blocking (void);
 
+bool stream_enqueue_realtime_command (char c);
+
 #ifdef DEBUGOUT
+void debug_write (const char *s);
 void debug_stream_init (io_stream_t *stream);
 #endif
 
diff --git a/system.c b/system.c
index e37e68f..c11db1c 100644
--- a/system.c
+++ b/system.c
@@ -35,7 +35,9 @@
 
 static status_code_t jog (sys_state_t state, char *args);
 static status_code_t enumerate_alarms (sys_state_t state, char *args);
+static status_code_t enumerate_alarms_grblformatted (sys_state_t state, char *args);
 static status_code_t enumerate_errors (sys_state_t state, char *args);
+static status_code_t enumerate_errors_grblformatted (sys_state_t state, char *args);
 static status_code_t enumerate_groups (sys_state_t state, char *args);
 static status_code_t enumerate_settings (sys_state_t state, char *args);
 static status_code_t enumerate_all (sys_state_t state, char *args);
@@ -210,7 +212,9 @@ PROGMEM static const sys_command_t sys_commands[] = {
     { "N0", false, set_startup_line0 },
     { "N1", false, set_startup_line1 },
     { "EA", true, enumerate_alarms },
+    { "EAG", true, enumerate_alarms_grblformatted },
     { "EE", true, enumerate_errors },
+    { "EEG", true, enumerate_errors_grblformatted },
     { "EG", true, enumerate_groups },
     { "ES", true, enumerate_settings },
     { "ESG", true, enumerate_settings_grblformatted },
@@ -340,12 +344,22 @@ static status_code_t jog (sys_state_t state, char *args)
 
 static status_code_t enumerate_alarms (sys_state_t state, char *args)
 {
-    return report_alarm_details();
+    return report_alarm_details(false);
+}
+
+static status_code_t enumerate_alarms_grblformatted (sys_state_t state, char *args)
+{
+    return report_alarm_details(true);
 }
 
 static status_code_t enumerate_errors (sys_state_t state, char *args)
 {
-    return report_error_details();
+    return report_error_details(false);
+}
+
+static status_code_t enumerate_errors_grblformatted (sys_state_t state, char *args)
+{
+    return report_error_details(true);
 }
 
 static status_code_t enumerate_groups (sys_state_t state, char *args)
@@ -370,8 +384,8 @@ static status_code_t enumerate_settings_halformatted (sys_state_t state, char *a
 
 static status_code_t enumerate_all (sys_state_t state, char *args)
 {
-    report_alarm_details();
-    report_error_details();
+    report_alarm_details(false);
+    report_error_details(false);
     report_setting_group_details(true, NULL);
     return report_settings_details(SettingsFormat_MachineReadable, Setting_SettingsAll, Group_All);
 }