diff --git a/Grbl_Esp32/src/Pin.cpp b/Grbl_Esp32/src/Pin.cpp
index 05bc9d4f..9564108f 100644
--- a/Grbl_Esp32/src/Pin.cpp
+++ b/Grbl_Esp32/src/Pin.cpp
@@ -27,14 +27,14 @@
 
 #ifdef ESP32
 #    include "Grbl.h"  // serial output
-#    define pin_error(...) info_serial(__VA_ARGS__)
+#    define pin_error(...) error_serial(__VA_ARGS__)
 #else
 #    define pin_error(...)                                                                                                                 \
         {}
 #endif
 
 #if defined PIN_DEBUG
-#    define pin_debug(...) pin_error(__VA_ARGS__)
+#    define pin_debug(...) debug_serial(__VA_ARGS__)
 #else
 #    define pin_debug(...)                                                                                                                 \
         {}
@@ -129,7 +129,7 @@ bool Pin::parse(StringRange tmp, Pins::PinDetail*& pinImplementation) {
         pinImplementation = new Pins::VoidPinDetail();
         return true;
     }
-    pin_error("Unknown prefix: \"%s\"\r\n", prefix.c_str());
+    pin_error("ERR: Unknown prefix: \"%s\"\r\n", prefix.c_str());
     return false;
 }
 
@@ -148,7 +148,7 @@ Pin Pin::create(const StringRange& str) {
 
         return Pin(pinImplementation);
     } catch (const AssertionFailed& ex) {  // We shouldn't get here under normal circumstances.
-        pin_error("Setting up pin [%s] failed. Details: %s\r\n", str.str().c_str(), ex.what());
+        pin_error("ERR: Setting up pin [%s] failed. Details: %s", str.str().c_str(), ex.what());
         (void)ex;  // Get rid of compiler warning
 
         return Pin(new Pins::ErrorPinDetail(str.str()));
diff --git a/Grbl_Esp32/src/Pins/GPIOPinDetail.cpp b/Grbl_Esp32/src/Pins/GPIOPinDetail.cpp
index 379df6dd..9cebe6c9 100644
--- a/Grbl_Esp32/src/Pins/GPIOPinDetail.cpp
+++ b/Grbl_Esp32/src/Pins/GPIOPinDetail.cpp
@@ -27,6 +27,8 @@ extern "C" int  __digitalRead(uint8_t pin);
 extern "C" void __digitalWrite(uint8_t pin, uint8_t val);
 
 namespace Pins {
+    std::vector<bool> GPIOPinDetail::_claimed(nGPIOPins, false);
+
     PinCapabilities GPIOPinDetail::GetDefaultCapabilities(uint8_t index) {
         // See https://randomnerdtutorials.com/esp32-pinout-reference-gpios/ for an overview:
         switch (index) {
@@ -103,6 +105,7 @@ namespace Pins {
         // WILL get into trouble.
 
         Assert(_capabilities != PinCapabilities::None, "Bad GPIO number");
+        Assert(!_claimed[index], "Pin is already used.");
 
         // User defined pin capabilities
         for (auto opt : options) {
@@ -118,6 +121,7 @@ namespace Pins {
                 Assert(false, "Bad GPIO option passed to pin %d: %s", int(index), opt());
             }
         }
+        _claimed[index] = true;
 
         // readWriteMask is xor'ed with the value to invert it if active low
         _readWriteMask = _attributes.has(PinAttributes::ActiveLow);
diff --git a/Grbl_Esp32/src/Pins/GPIOPinDetail.h b/Grbl_Esp32/src/Pins/GPIOPinDetail.h
index bbbd15a5..54e7a5b0 100644
--- a/Grbl_Esp32/src/Pins/GPIOPinDetail.h
+++ b/Grbl_Esp32/src/Pins/GPIOPinDetail.h
@@ -28,6 +28,9 @@ namespace Pins {
 
         static PinCapabilities GetDefaultCapabilities(uint8_t index);
 
+        static const int         nGPIOPins = 40;
+        static std::vector<bool> _claimed;
+
     public:
         GPIOPinDetail(uint8_t index, PinOptionsParser options);
 
@@ -45,7 +48,7 @@ namespace Pins {
 
         String toString() override;
 
-        ~GPIOPinDetail() override {}
+        ~GPIOPinDetail() override { _claimed[_index] = false; }
     };
 
 }
diff --git a/Grbl_Esp32/src/Pins/I2SOPinDetail.cpp b/Grbl_Esp32/src/Pins/I2SOPinDetail.cpp
index 0a2b4df1..2433f40c 100644
--- a/Grbl_Esp32/src/Pins/I2SOPinDetail.cpp
+++ b/Grbl_Esp32/src/Pins/I2SOPinDetail.cpp
@@ -25,9 +25,12 @@
 extern "C" void __digitalWrite(uint8_t pin, uint8_t val);
 
 namespace Pins {
+    std::vector<bool> I2SOPinDetail::_claimed(nI2SOPins, false);
+
     I2SOPinDetail::I2SOPinDetail(uint8_t index, const PinOptionsParser& options) :
         PinDetail(index), _capabilities(PinCapabilities::Output | PinCapabilities::I2S), _attributes(Pins::PinAttributes::Undefined),
         _readWriteMask(0) {
+        Assert(!_claimed[index], "Pin is already used.");
         // User defined pin capabilities
         for (auto opt : options) {
             if (opt.is("low")) {
@@ -38,6 +41,7 @@ namespace Pins {
                 Assert(false, "Unsupported I2SO option '%s'", opt());
             }
         }
+        _claimed[index] = true;
 
         // readWriteMask is xor'ed with the value to invert it if active low
         _readWriteMask = _attributes.has(PinAttributes::ActiveLow);
diff --git a/Grbl_Esp32/src/Pins/I2SOPinDetail.h b/Grbl_Esp32/src/Pins/I2SOPinDetail.h
index a48dfd70..a83e4945 100644
--- a/Grbl_Esp32/src/Pins/I2SOPinDetail.h
+++ b/Grbl_Esp32/src/Pins/I2SOPinDetail.h
@@ -27,6 +27,9 @@ namespace Pins {
         PinAttributes   _attributes;
         int             _readWriteMask;
 
+        static const int         nI2SOPins = 32;
+        static std::vector<bool> _claimed;
+
     public:
         I2SOPinDetail(uint8_t index, const PinOptionsParser& options);
 
@@ -40,7 +43,7 @@ namespace Pins {
 
         String toString() override;
 
-        ~I2SOPinDetail() override {}
+        ~I2SOPinDetail() override { _claimed[_index] = false; }
     };
 }
 
diff --git a/Grbl_Esp32/src/Pins/PinDetail.h b/Grbl_Esp32/src/Pins/PinDetail.h
index 7eb6c91a..d6ca4ceb 100644
--- a/Grbl_Esp32/src/Pins/PinDetail.h
+++ b/Grbl_Esp32/src/Pins/PinDetail.h
@@ -25,6 +25,7 @@
 #include <WString.h>
 #include <cstdint>
 #include <cstring>
+#include <vector>
 
 namespace Pins {