diff --git a/FluidNC/src/Pin.cpp b/FluidNC/src/Pin.cpp
index 5e22afacf..829493dcc 100644
--- a/FluidNC/src/Pin.cpp
+++ b/FluidNC/src/Pin.cpp
@@ -10,8 +10,11 @@
 #include "Pins/GPIOPinDetail.h"
 #include "Pins/VoidPinDetail.h"
 #include "Pins/I2SOPinDetail.h"
+#include "Pins/UARTPinDetail.h"
 #include "Pins/ErrorPinDetail.h"
 #include "string_util.h"
+#include "Machine/MachineConfig.h"  // config
+#include <string_view>
 
 Pins::PinDetail* Pin::undefinedPin = new Pins::VoidPinDetail();
 Pins::PinDetail* Pin::errorPin     = new Pins::ErrorPinDetail("unknown");
@@ -73,8 +76,28 @@ const char* Pin::parse(std::string_view pin_str, Pins::PinDetail*& pinImplementa
         pinImplementation = new Pins::GPIOPinDetail(static_cast<pinnum_t>(pin_number), parser);
     }
     if (string_util::equal_ignore_case(prefix, "i2so")) {
+        if (config->_i2so == nullptr) {
+            return "i2so: section must be defined before using i2so pins";
+        }
         pinImplementation = new Pins::I2SOPinDetail(static_cast<pinnum_t>(pin_number), parser);
     }
+
+    if (prefix.length() == 13) {
+        if (prefix.substr(0, 12) == "uart_channel") {
+            log_info("More:" << prefix[12]);
+            if (prefix[12] >= '0' && prefix[12] <= '2') {  // TODO use MAX_N_UARTS
+                // check to see if the channel exits
+                auto deviceId = prefix[12] - '0';
+                if (config->_uart_channels[deviceId] == nullptr) {
+                    return " uart channel number not found";
+                }
+                pinImplementation = new Pins::UARTIODetail(deviceId, pinnum_t(pin_number), parser);
+            } else {
+                return "Incorrect pin extender specification. Expected 'pinext[0-2].[port number]'.";
+            }
+            }
+    }
+
     if (string_util::equal_ignore_case(prefix, "no_pin")) {
         pinImplementation = undefinedPin;
     }
diff --git a/FluidNC/src/Pins/PinCapabilities.cpp b/FluidNC/src/Pins/PinCapabilities.cpp
index 1b8c6d0cf..3e54bb00a 100644
--- a/FluidNC/src/Pins/PinCapabilities.cpp
+++ b/FluidNC/src/Pins/PinCapabilities.cpp
@@ -29,6 +29,7 @@ namespace Pins {
 
     PinCapabilities PinCapabilities::Native(1 << (__LINE__ - START_LINE));
     PinCapabilities PinCapabilities::I2S(1 << (__LINE__ - START_LINE));
+    PinCapabilities PinCapabilities::UARTIO(1 << (__LINE__ - START_LINE));
     PinCapabilities PinCapabilities::Error(1 << (__LINE__ - START_LINE));
     PinCapabilities PinCapabilities::Void(1 << (__LINE__ - START_LINE));
 }
diff --git a/FluidNC/src/Pins/PinCapabilities.h b/FluidNC/src/Pins/PinCapabilities.h
index ea9849d2c..f457115f1 100644
--- a/FluidNC/src/Pins/PinCapabilities.h
+++ b/FluidNC/src/Pins/PinCapabilities.h
@@ -21,7 +21,7 @@ namespace Pins {
         friend class PinAttributes;  // Wants access to _value for validation
 
     public:
-        PinCapabilities(const PinCapabilities&) = default;
+        PinCapabilities(const PinCapabilities&)            = default;
         PinCapabilities& operator=(const PinCapabilities&) = default;
 
         // All the capabilities we use and test:
@@ -44,6 +44,7 @@ namespace Pins {
         // can compare classes of pins along with their properties by just looking at the capabilities.
         static PinCapabilities Native;
         static PinCapabilities I2S;
+        static PinCapabilities UARTIO;
         static PinCapabilities Error;
         static PinCapabilities Void;
 
diff --git a/FluidNC/src/Pins/UARTPinDetail.cpp b/FluidNC/src/Pins/UARTPinDetail.cpp
new file mode 100644
index 000000000..34ae4b280
--- /dev/null
+++ b/FluidNC/src/Pins/UARTPinDetail.cpp
@@ -0,0 +1,107 @@
+// Copyright (c) 2023 Bart Dring
+// Use of this source code is governed by a GPLv3 license that can be found in the LICENSE file.
+
+#ifdef ESP32
+#    include "UARTPinDetail.h"
+#    include "PinDetail.h"
+
+#    include "../I2SOut.h"
+#    include "../Assert.h"
+
+namespace Pins {
+    std::vector<bool> UARTIODetail::_claimed(nPins, false);
+
+    UARTIODetail::UARTIODetail(int deviceId, pinnum_t index, const PinOptionsParser& options) :
+        PinDetail(index), _capabilities(PinCapabilities::Output | PinCapabilities::UARTIO), _attributes(Pins::PinAttributes::Undefined),
+        _readWriteMask(0) {
+        Assert(index < nPins, "Pin number is greater than max %d", nPins - 1);
+        Assert(!_claimed[index], "Pin is already used.");
+
+        // User defined pin capabilities
+        for (auto opt : options) {
+            if (opt.is("pu")) {
+            } else if (opt.is("pd")) {
+            } else if (opt.is("low")) {
+                _attributes = _attributes | PinAttributes::ActiveLow;
+            } else if (opt.is("high")) {
+                // Default: Active HIGH.
+            } else {
+                Assert(false, "Bad UARTPin option passed to pin %d: %s", int(index), opt());
+            }
+        }
+
+        _device_id = deviceId;
+
+        //log_info("created uart pin:" << index);
+        _claimed[index] = true;
+
+        // readWriteMask is xor'ed with the value to invert it if active low
+        _readWriteMask = int(_attributes.has(PinAttributes::ActiveLow));
+    }
+    // The write will not happen immediately; the data is queued for
+    // delivery to the serial shift register chain via DMA and a FIFO
+
+    PinCapabilities UARTIODetail::capabilities() const {
+        return PinCapabilities::Output | PinCapabilities::UARTIO;
+    }
+
+    void IRAM_ATTR UARTIODetail::write(int high) {
+        if (high != _lastWrittenValue) {
+            _lastWrittenValue = high;
+            if (!_attributes.has(PinAttributes::Output)) {
+                log_error(toString());
+            }
+            Assert(_attributes.has(PinAttributes::Output), "Pin %s cannot be written", toString().c_str());
+            int value = _readWriteMask ^ high;
+            log_info("Set uart pin:" << high);
+        }
+    }
+
+    int UARTIODetail::read() {
+        return 0;
+    }
+
+    void UARTIODetail::setAttr(PinAttributes value) {
+        // These two assertions will fail if we do them for index 1/3 (Serial uart). This is because
+        // they are initialized by HardwareSerial well before we start our main operations. Best to
+        // just ignore them for now, and figure this out later. TODO FIXME!
+
+        // Check the attributes first:
+        Assert(value.validateWith(this->_capabilities) || _index == 1 || _index == 3,
+               "The requested attributes don't match the capabilities for %s",
+               toString().c_str());
+        Assert(!_attributes.conflictsWith(value) || _index == 1 || _index == 3,
+               "The requested attributes on %s conflict with previous settings",
+               toString().c_str());
+
+        _attributes = _attributes | value;
+
+        // If the pin is ActiveLow, we should take that into account here:
+        if (value.has(PinAttributes::Output)) {
+            //gpio_write(_index, int(value.has(PinAttributes::InitialOn)) ^ _readWriteMask);
+        }
+    }
+
+    PinAttributes UARTIODetail::getAttr() const {
+        return _attributes;
+    }
+
+    std::string UARTIODetail::toString() {
+        std::string s("uart_channel");
+        s += std::to_string(_device_id);
+        s += ".";
+        s += std::to_string(_index);
+        if (_attributes.has(PinAttributes::ActiveLow)) {
+            s += ":low";
+        }
+        if (_attributes.has(PinAttributes::PullUp)) {
+            s += ":pu";
+        }
+        if (_attributes.has(PinAttributes::PullDown)) {
+            s += ":pd";
+        }
+        return s;
+    }
+}
+
+#endif
diff --git a/FluidNC/src/Pins/UARTPinDetail.h b/FluidNC/src/Pins/UARTPinDetail.h
new file mode 100644
index 000000000..4137f295a
--- /dev/null
+++ b/FluidNC/src/Pins/UARTPinDetail.h
@@ -0,0 +1,38 @@
+// Copyright (c) 2023 B. Dring
+// Use of this source code is governed by a GPLv3 license that can be found in the LICENSE file.
+
+#pragma once
+#ifdef ESP32
+
+#    include "PinDetail.h"
+
+namespace Pins {
+    class UARTIODetail : public PinDetail {
+        PinCapabilities _capabilities;
+        PinAttributes   _attributes;
+        int             _readWriteMask;
+
+        int _device_id;
+
+        static const int         nPins = 255;
+        static std::vector<bool> _claimed;
+
+        bool _lastWrittenValue = false;
+
+    public:
+        UARTIODetail(int deviceId, pinnum_t index, const PinOptionsParser& options);
+
+        // I/O:
+        PinCapabilities capabilities() const override;
+        void          write(int high) override;
+        int           read() override;
+        void          setAttr(PinAttributes value) override;
+        PinAttributes getAttr() const override;
+
+        std::string toString() override;
+
+        ~UARTIODetail() override { _claimed[_index] = false; }
+    };
+}
+
+#endif
diff --git a/FluidNC/src/UartChannel.cpp b/FluidNC/src/UartChannel.cpp
index f304f8802..8cd56f158 100644
--- a/FluidNC/src/UartChannel.cpp
+++ b/FluidNC/src/UartChannel.cpp
@@ -20,6 +20,7 @@ void UartChannel::init() {
 void UartChannel::init(Uart* uart) {
     _uart = uart;
     allChannels.registration(this);
+    log_info("uart_channel" << _uart_num << " created");
 }
 
 size_t UartChannel::write(uint8_t c) {
diff --git a/FluidNC/src/UartChannel.h b/FluidNC/src/UartChannel.h
index 94f9aec5f..dbbca4e4c 100644
--- a/FluidNC/src/UartChannel.h
+++ b/FluidNC/src/UartChannel.h
@@ -12,7 +12,8 @@ class UartChannel : public Channel, public Configuration::Configurable {
     Lineedit* _lineedit;
     Uart*     _uart;
 
-    int _uart_num = 0;
+    int  _uart_num = 0;
+    bool _has_pins = false;  // the device is a pin extender
 
 public:
     UartChannel(bool addCR = false);
@@ -39,7 +40,10 @@ class UartChannel : public Channel, public Configuration::Configurable {
     Channel* pollLine(char* line) override;
 
     // Configuration methods
-    void group(Configuration::HandlerBase& handler) override { handler.item("uart_num", _uart_num); }
+    void group(Configuration::HandlerBase& handler) override { 
+        handler.item("uart_num", _uart_num);
+        handler.item("has_pins", _has_pins);
+    }
 };
 
 extern UartChannel Uart0;