diff --git a/Grbl_Esp32/src/Grbl.cpp b/Grbl_Esp32/src/Grbl.cpp
index fcb808ba..769bd434 100644
--- a/Grbl_Esp32/src/Grbl.cpp
+++ b/Grbl_Esp32/src/Grbl.cpp
@@ -77,10 +77,11 @@ void grbl_init() {
         WebUI::inputBuffer.begin();
     } catch (const AssertionFailed& ex) {
         // This means something is terribly broken:
-        grbl_sendf(CLIENT_ALL, "Critical error in run_once: %s", ex.stackTrace.c_str());
-        while (true) {
-            sleep(1000);
-        }
+
+        // Should grbl_sendf always work? Serial is initialized first, so after line 34 it should.
+        grbl_msg_sendf(CLIENT_ALL, MsgLevel::Error, "Critical error in run_once: %s", ex.stackTrace.c_str());
+        sleep(10000);
+        throw;
     }
 }
 
@@ -127,10 +128,9 @@ void run_once() {
         protocol_main_loop();
     } catch (const AssertionFailed& ex) {
         // This means something is terribly broken:
-        grbl_sendf(CLIENT_ALL, "Critical error in run_once: %s", ex.stackTrace.c_str());
-        while (true) {
-            sleep(1000);
-        }
+        grbl_msg_sendf(CLIENT_ALL, MsgLevel::Error, "Critical error in run_once: %s", ex.stackTrace.c_str());
+        sleep(10000);
+        throw;
     }
 }
 
diff --git a/Grbl_Esp32/src/Limits.cpp b/Grbl_Esp32/src/Limits.cpp
index 37065c42..85592b08 100644
--- a/Grbl_Esp32/src/Limits.cpp
+++ b/Grbl_Esp32/src/Limits.cpp
@@ -309,10 +309,11 @@ uint8_t limit_mask = 0;
 
 void limits_init() {
     limit_mask     = 0;
-    Pin::Attr mode = Pin::Attr::Input | Pin::Attr::PullUp;
+    Pin::Attr mode = Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR;
 #ifdef DISABLE_LIMIT_PIN_PULL_UP
-    mode = Pin::Attr::Input;
+    mode = Pin::Attr::Input | Pin::Attr::ISR;
 #endif
+
     auto n_axis = number_axis->get();
     for (int axis = 0; axis < n_axis; axis++) {
         for (int gang_index = 0; gang_index < 2; gang_index++) {
diff --git a/Grbl_Esp32/src/PinSettingsDefinitions.cpp b/Grbl_Esp32/src/PinSettingsDefinitions.cpp
index 6da4f48b..b60d887a 100644
--- a/Grbl_Esp32/src/PinSettingsDefinitions.cpp
+++ b/Grbl_Esp32/src/PinSettingsDefinitions.cpp
@@ -177,7 +177,6 @@ const char* USER_ANALOG_PIN_2_DEFAULT = USER_ANALOG_PIN_2;
 #endif
 const char* USER_ANALOG_PIN_3_DEFAULT = USER_ANALOG_PIN_3;
 
-
 #ifndef SPINDLE_OUTPUT_PIN
 #    define SPINDLE_OUTPUT_PIN UNDEFINED_PIN
 #endif
@@ -866,9 +865,9 @@ void make_pin_settings() {
     MacroButton3Pin      = new PinSetting("Macro/3/Pin", MACRO_BUTTON_3_PIN_DEFAULT);
 
     // XXX Move to Dynamixel class
-    DynamixelTXDPin      = new PinSetting("Dynamixel/TXD/Pin", DYNAMIXEL_TXD_DEFAULT);
-    DynamixelRXDPin      = new PinSetting("Dynamixel/RXD/Pin", DYNAMIXEL_RXD_DEFAULT);
-    DynamixelRTSPin      = new PinSetting("Dynamixel/RTS/Pin", DYNAMIXEL_RTS_DEFAULT);
+    DynamixelTXDPin = new PinSetting("Dynamixel/TXD/Pin", DYNAMIXEL_TXD_DEFAULT);
+    DynamixelRXDPin = new PinSetting("Dynamixel/RXD/Pin", DYNAMIXEL_RXD_DEFAULT);
+    DynamixelRTSPin = new PinSetting("Dynamixel/RTS/Pin", DYNAMIXEL_RTS_DEFAULT);
 
     // User pins:
     UserDigitalPin[0] = new PinSetting("UserDigital/0/Pin", USER_DIGITAL_PIN_0_DEFAULT);
@@ -887,9 +886,9 @@ void make_pin_settings() {
     SpindleForwardPin   = new PinSetting("Spindle/Forward/Pin", SPINDLE_FORWARD_PIN_DEFAULT);
     SpindleReversePin   = new PinSetting("Spindle/Reverse/Pin", SPINDLE_REVERSE_PIN_DEFAULT);
     // XXX Move to VFD class
-    VFDRS485TXDPin      = new PinSetting("Spindle/VFD/TxD/Pin", VFD_RS485_TXD_PIN_DEFAULT);  // VFD_RS485_TXD_PIN
-    VFDRS485RXDPin      = new PinSetting("Spindle/VFD/RxD/Pin", VFD_RS485_RXD_PIN_DEFAULT);  // VFD_RS485_RXD_PIN
-    VFDRS485RTSPin      = new PinSetting("Spindle/VFD/RTS/Pin", VFD_RS485_RTS_PIN_DEFAULT);  // VFD_RS485_RTS_PIN
+    VFDRS485TXDPin = new PinSetting("Spindle/VFD/TxD/Pin", VFD_RS485_TXD_PIN_DEFAULT);  // VFD_RS485_TXD_PIN
+    VFDRS485RXDPin = new PinSetting("Spindle/VFD/RxD/Pin", VFD_RS485_RXD_PIN_DEFAULT);  // VFD_RS485_RXD_PIN
+    VFDRS485RTSPin = new PinSetting("Spindle/VFD/RTS/Pin", VFD_RS485_RTS_PIN_DEFAULT);  // VFD_RS485_RTS_PIN
 
     // Axis:
     LimitPins[X_AXIS][0] = new PinSetting("X/Limit/Pin", X_LIMIT_PIN_DEFAULT);
diff --git a/Grbl_Esp32/src/Pins/GPIOPinDetail.cpp b/Grbl_Esp32/src/Pins/GPIOPinDetail.cpp
index 04605f0c..e7563e41 100644
--- a/Grbl_Esp32/src/Pins/GPIOPinDetail.cpp
+++ b/Grbl_Esp32/src/Pins/GPIOPinDetail.cpp
@@ -143,6 +143,12 @@ namespace Pins {
             pinModeValue |= OUTPUT;
         }
 
+        // TODO FIXME: For now, I added PU capabilities to 'value' as well. This *should* be removed once the
+        // code that uses #define's to decide this is gone.
+        if (value.has(PinAttributes::PullUp)) {
+            pinModeValue |= PULLUP;
+        }
+
         // PU/PD should be specified by the user. Code has nothing to do with them:
         if (_attributes.has(PinAttributes::PullUp)) {
             pinModeValue |= PULLUP;
@@ -161,12 +167,14 @@ namespace Pins {
     }
 
     void GPIOPinDetail::attachInterrupt(void (*callback)(void*), void* arg, int mode) {
-        Assert(_capabilities.has(PinCapabilities::ISR), "Pin has no ISR capability defined. Cannot bind ISR.");
+        Assert(_attributes.has(PinAttributes::ISR),
+               "Pin has no ISR attribute, which means 'setAttr' was not set, or the pin doesn't support ISR's. Cannot bind ISR.");
         ::attachInterruptArg(_index, callback, arg, mode);
     }
 
     void GPIOPinDetail::detachInterrupt() {
-        Assert(_capabilities.has(PinCapabilities::ISR), "Pin has no ISR capability defined. Cannot unbind ISR.");
+        Assert(_attributes.has(PinAttributes::ISR),
+               "Pin has no ISR attribute, which means 'setAttr' was not set, or the pin doesn't support ISR's. Cannot unbind ISR.");
         ::detachInterrupt(_index);
     }
 
diff --git a/Grbl_Esp32/src/System.cpp b/Grbl_Esp32/src/System.cpp
index fed1a0b2..f9695b3e 100644
--- a/Grbl_Esp32/src/System.cpp
+++ b/Grbl_Esp32/src/System.cpp
@@ -48,42 +48,42 @@ void system_ini() {  // Renamed from system_init() due to conflict with esp32 fi
     // setup control inputs
 
     if (ControlSafetyDoorPin->get() != Pin::UNDEFINED) {
-        ControlSafetyDoorPin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp);
+        ControlSafetyDoorPin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR);
         ControlSafetyDoorPin->get().attachInterrupt(isr_control_inputs, CHANGE);
     }
 
     if (ControlResetPin->get() != Pin::UNDEFINED) {
-        ControlResetPin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp);
+        ControlResetPin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR);
         ControlResetPin->get().attachInterrupt(isr_control_inputs, CHANGE);
     }
 
     if (ControlFeedHoldPin->get() != Pin::UNDEFINED) {
-        ControlFeedHoldPin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp);
+        ControlFeedHoldPin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR);
         ControlFeedHoldPin->get().attachInterrupt(isr_control_inputs, CHANGE);
     }
 
     if (ControlCycleStartPin->get() != Pin::UNDEFINED) {
-        ControlCycleStartPin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp);
+        ControlCycleStartPin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR);
         ControlCycleStartPin->get().attachInterrupt(isr_control_inputs, CHANGE);
     }
 
     if (MacroButton0Pin->get() != Pin::UNDEFINED) {
-        MacroButton0Pin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp);
+        MacroButton0Pin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR);
         MacroButton0Pin->get().attachInterrupt(isr_control_inputs, CHANGE);
     }
 
     if (MacroButton1Pin->get() != Pin::UNDEFINED) {
-        MacroButton1Pin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp);
+        MacroButton1Pin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR);
         MacroButton1Pin->get().attachInterrupt(isr_control_inputs, CHANGE);
     }
 
     if (MacroButton2Pin->get() != Pin::UNDEFINED) {
-        MacroButton2Pin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp);
+        MacroButton2Pin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR);
         MacroButton2Pin->get().attachInterrupt(isr_control_inputs, CHANGE);
     }
 
     if (MacroButton3Pin->get() != Pin::UNDEFINED) {
-        MacroButton3Pin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp);
+        MacroButton3Pin->get().setAttr(Pin::Attr::Input | Pin::Attr::PullUp | Pin::Attr::ISR);
         MacroButton3Pin->get().attachInterrupt(isr_control_inputs, CHANGE);
     }