diff --git a/Config.h b/Config.h
index b7d146f..35c7e52 100644
--- a/Config.h
+++ b/Config.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2017,2018 by Andy Uribe CA6JAU
+ *   Copyright (C) 2017,2018,2019 by Andy Uribe CA6JAU
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -58,6 +58,10 @@
 // Host communication selection:
 // #define STM32_USART1_HOST
 #define STM32_USB_HOST
+// #define STM32_I2C_HOST
+
+// I2C host address:
+#define I2C_ADDR 0x22
 
 // Enable mode detection:
 #define ENABLE_SCAN_MODE
diff --git a/Globals.h b/Globals.h
index d50e1c2..ffc0ad8 100644
--- a/Globals.h
+++ b/Globals.h
@@ -1,6 +1,6 @@
 /*
  *   Copyright (C) 2015,2016 by Jonathan Naylor G4KLX
- *   Copyright (C) 2016,2017,2018 by Andy Uribe CA6JAU
+ *   Copyright (C) 2016,2017,2018,2019 by Andy Uribe CA6JAU
  *   Copyright (C) 2019 by Florian Wolters DF2ET
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -85,6 +85,7 @@ const uint8_t  MARK_NONE  = 0x00U;
 #include "CalDMR.h"
 #include "Debug.h"
 #include "Utils.h"
+#include "I2CHost.h"
 
 extern MMDVM_STATE m_modemState;
 extern MMDVM_STATE m_calState;
@@ -145,5 +146,9 @@ extern CCalRSSI calRSSI;
 
 extern CCWIdTX cwIdTX;
 
+#if defined(STM32_I2C_HOST)
+extern CI2CHost i2c;
+#endif
+
 #endif
 
diff --git a/I2CHost.cpp b/I2CHost.cpp
new file mode 100644
index 0000000..e80a096
--- /dev/null
+++ b/I2CHost.cpp
@@ -0,0 +1,201 @@
+/*
+ *   Copyright (C) 2019 by Andy Uribe CA6JAU
+ *
+ *   This program 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 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program 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 this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "Config.h"
+
+#if defined(STM32_I2C_HOST)
+
+#include "Globals.h"
+#include "I2CHost.h"
+
+extern "C" {
+  void I2C2_EV_IRQHandler(void) {
+    i2c.I2C_EVHandler();
+  }
+
+  void I2C2_ER_IRQHandler(void) {
+    if (I2C_GetITStatus(I2C2, I2C_IT_AF)) {
+      I2C_ClearITPendingBit(I2C2, I2C_IT_AF);
+    }
+  }
+}
+
+CI2CHost::CI2CHost()
+{
+}
+
+void CI2CHost::Init(void)
+{
+  GPIO_InitTypeDef  GPIO_InitStructure;
+  NVIC_InitTypeDef NVIC_InitStructure;
+  I2C_InitTypeDef  I2C_InitStructure;
+
+  RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C2, ENABLE);
+  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
+  RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
+
+  // Configure I2C GPIOs
+  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_10 | GPIO_Pin_11;
+  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
+  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_OD;
+  GPIO_Init(GPIOB, &GPIO_InitStructure);
+
+  // Configure the I2C event interrupt
+  NVIC_InitStructure.NVIC_IRQChannel                   = I2C2_EV_IRQn;
+  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 15;
+  NVIC_InitStructure.NVIC_IRQChannelSubPriority        = 15;
+  NVIC_InitStructure.NVIC_IRQChannelCmd                = ENABLE;
+  NVIC_Init(&NVIC_InitStructure);
+
+  // Configure the I2C error interrupt
+  NVIC_InitStructure.NVIC_IRQChannel = I2C2_ER_IRQn;
+  NVIC_Init(&NVIC_InitStructure);
+
+  // I2C configuration
+  I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;
+  I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;
+  I2C_InitStructure.I2C_OwnAddress1 = I2C_ADDR << 1;
+  I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;
+  I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;
+  I2C_InitStructure.I2C_ClockSpeed = I2C_CLK_FREQ;
+
+  // Enable I2C
+  I2C_Cmd(I2C2, ENABLE);
+  // Apply I2C configuration
+  I2C_Init(I2C2, &I2C_InitStructure);
+
+  I2C_ITConfig(I2C2, I2C_IT_EVT, ENABLE);
+  I2C_ITConfig(I2C2, I2C_IT_BUF, ENABLE);
+  I2C_ITConfig(I2C2, I2C_IT_ERR, ENABLE);
+
+  // Initialize the FIFOs
+  txFIFO_head = 0U;
+  txFIFO_tail = 0U;
+  rxFIFO_head = 0U;
+  rxFIFO_tail = 0U;
+}
+
+void CI2CHost::I2C_EVHandler(void) {
+  uint32_t event = I2C_GetLastEvent(I2C2);
+
+  switch (event) {
+    case I2C_EVENT_SLAVE_RECEIVER_ADDRESS_MATCHED:
+      break;
+    case I2C_EVENT_SLAVE_BYTE_RECEIVED:
+      if (rxFIFO_level() < I2C_RX_FIFO_SIZE) {
+        rxFIFO[rxFIFO_head] = I2C_ReceiveData(I2C2);
+        rxFIFO_head++;
+        if (rxFIFO_head >= I2C_RX_FIFO_SIZE)
+          rxFIFO_head = 0U;
+      } else
+        I2C_ReceiveData(I2C2);
+      break;
+    case I2C_EVENT_SLAVE_TRANSMITTER_ADDRESS_MATCHED:
+    case I2C_EVENT_SLAVE_BYTE_TRANSMITTED:
+      if (txFIFO_level() > 0) {
+        I2C_SendData(I2C2, txFIFO[txFIFO_tail]);
+        txFIFO_tail++;
+        if (txFIFO_tail >= I2C_TX_FIFO_SIZE)
+          txFIFO_tail = 0U;
+      } else
+        I2C_SendData(I2C2, 0U);
+      break;
+    case I2C_EVENT_SLAVE_STOP_DETECTED:
+      I2C2_ClearFlag();
+      break;
+  }
+}
+
+void CI2CHost::I2C2_ClearFlag(void) {
+  // Clear ADDR flag
+  while((I2C2->SR1 & I2C_SR1_ADDR) == I2C_SR1_ADDR) {
+    I2C2->SR1;
+    I2C2->SR2;
+  }
+
+  // Clear STOPF flag
+  while((I2C2->SR1 & I2C_SR1_STOPF) == I2C_SR1_STOPF) {
+    I2C2->SR1;
+    I2C2->CR1 |= 0x1;
+  }
+}
+
+uint16_t CI2CHost::txFIFO_level(void)
+{
+  uint32_t tail = txFIFO_tail;
+  uint32_t head = txFIFO_head;
+
+  if (tail > head)
+    return I2C_TX_FIFO_SIZE + head - tail;
+  else
+    return head - tail;
+}
+
+uint16_t CI2CHost::rxFIFO_level(void)
+{
+  uint32_t tail = rxFIFO_tail;
+  uint32_t head = rxFIFO_head;
+
+  if (tail > head)
+    return I2C_RX_FIFO_SIZE + head - tail;
+  else
+    return head - tail;
+}
+
+
+uint8_t CI2CHost::txFIFO_put(uint8_t next)
+{
+  if (txFIFO_level() < I2C_TX_FIFO_SIZE) {
+    txFIFO[txFIFO_head] = next;
+
+    txFIFO_head++;
+    if (txFIFO_head >= I2C_TX_FIFO_SIZE)
+      txFIFO_head = 0U;
+    return 1U;
+  } else {
+    return 0U;
+  }
+}
+
+uint8_t CI2CHost::AvailI2C(void)
+{
+  if (rxFIFO_level() > 0U)
+    return 1U;
+  else
+    return 0U;
+}
+
+
+uint8_t CI2CHost::ReadI2C(void)
+{
+  uint8_t data_c = rxFIFO[rxFIFO_tail];
+
+  rxFIFO_tail++;
+  if (rxFIFO_tail >= I2C_RX_FIFO_SIZE)
+    rxFIFO_tail = 0U;
+
+  return data_c;
+}
+
+void CI2CHost::WriteI2C(const uint8_t* data, uint16_t length)
+{
+  for (uint16_t i = 0U; i < length; i++)
+    txFIFO_put(data[i]);
+}
+
+#endif
\ No newline at end of file
diff --git a/I2CHost.h b/I2CHost.h
new file mode 100644
index 0000000..cb168ed
--- /dev/null
+++ b/I2CHost.h
@@ -0,0 +1,55 @@
+/*
+ *   Copyright (C) 2019 by Andy Uribe CA6JAU
+ *
+ *   This program 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 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program 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 this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#if !defined(I2CHost_H)
+#define  I2CHost_H
+
+#include "Config.h"
+
+#if defined(STM32_I2C_HOST)
+
+#define I2C_CLK_FREQ       100000U
+#define I2C_TX_FIFO_SIZE   512U
+#define I2C_RX_FIFO_SIZE   512U
+
+class CI2CHost {
+public:
+  CI2CHost();
+
+  void    Init(void);
+  void    I2C_EVHandler(void);
+  uint8_t AvailI2C(void);
+  uint8_t ReadI2C(void);
+  void    WriteI2C(const uint8_t* data, uint16_t length);
+
+private:
+  void     I2C2_ClearFlag(void);
+  uint16_t txFIFO_level(void);
+  uint16_t rxFIFO_level(void);
+  uint8_t  txFIFO_put(uint8_t next);
+
+  volatile uint8_t  txFIFO[I2C_TX_FIFO_SIZE];
+  volatile uint8_t  rxFIFO[I2C_RX_FIFO_SIZE];
+  volatile uint16_t txFIFO_head, txFIFO_tail;
+  volatile uint16_t rxFIFO_head, rxFIFO_tail;
+
+};
+
+#endif
+
+#endif
diff --git a/MMDVM_HS.cpp b/MMDVM_HS.cpp
index f97a3be..cd61683 100644
--- a/MMDVM_HS.cpp
+++ b/MMDVM_HS.cpp
@@ -86,6 +86,10 @@ CCWIdTX    cwIdTX;
 CSerialPort serial;
 CIO io;
 
+#if defined(STM32_I2C_HOST)
+CI2CHost i2c;
+#endif
+
 void setup()
 {
   serial.start();
diff --git a/STM32F10X_Lib b/STM32F10X_Lib
index 2cf6b77..1debc23 160000
--- a/STM32F10X_Lib
+++ b/STM32F10X_Lib
@@ -1 +1 @@
-Subproject commit 2cf6b7712637a7961d52e0deee5f9b257bb9b9be
+Subproject commit 1debc23063f3942608e2bd62d04d5e1249c47fa3
diff --git a/SerialSTM.cpp b/SerialSTM.cpp
index 4363039..aae4117 100644
--- a/SerialSTM.cpp
+++ b/SerialSTM.cpp
@@ -1,6 +1,6 @@
 /*
  *   Copyright (C) 2016 by Jim McLaughlin KI6ZUM
- *   Copyright (C) 2016,2017 by Andy Uribe CA6JAU
+ *   Copyright (C) 2016,2017,2018,2019 by Andy Uribe CA6JAU
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -23,6 +23,7 @@
 
 #include "Globals.h"
 #include "SerialPort.h"
+#include "I2CHost.h"
 
 #if defined(STM32_USB_HOST)
 #include <usb_serial.h>
@@ -32,9 +33,9 @@
 Pin definitions:
 
 - Host communication:
-USART1 - TXD PA9  - RXD PA10
-or
-USB VCOM
+1) USART1 - TXD PA9  - RXD PA10
+2) USB VCOM
+3) I2C - SCL PB10 - SDA PB11
 
 - Serial repeater
 USART2 - TXD PA2  - RXD PA3 
@@ -441,6 +442,8 @@ void CSerialPort::beginInt(uint8_t n, int speed)
       InitUSART1(speed);
     #elif defined(STM32_USB_HOST)
       usbserial.begin();
+    #elif defined(STM32_I2C_HOST)
+      i2c.Init();
     #endif
       break;
     case 3U:
@@ -452,7 +455,7 @@ void CSerialPort::beginInt(uint8_t n, int speed)
       break;
     default:
       break;
-  }   
+  }
 }
 
 int CSerialPort::availableInt(uint8_t n)
@@ -463,6 +466,8 @@ int CSerialPort::availableInt(uint8_t n)
       return AvailUSART1();
     #elif defined(STM32_USB_HOST)
       return usbserial.available();
+    #elif defined(STM32_I2C_HOST)
+      return i2c.AvailI2C();
     #endif
     case 3U: 
     #if defined(SERIAL_REPEATER)
@@ -483,6 +488,8 @@ uint8_t CSerialPort::readInt(uint8_t n)
       return ReadUSART1();
     #elif defined(STM32_USB_HOST)
       return usbserial.read();
+    #elif defined(STM32_I2C_HOST)
+      return i2c.ReadI2C();
     #endif
     case 3U:
     #if defined(SERIAL_REPEATER)
@@ -501,12 +508,14 @@ void CSerialPort::writeInt(uint8_t n, const uint8_t* data, uint16_t length, bool
     case 1U:
     #if defined(STM32_USART1_HOST)
       WriteUSART1(data, length);
-    if (flush)
-      TXSerialFlush1();
+      if (flush)
+        TXSerialFlush1();
     #elif defined(STM32_USB_HOST)
       usbserial.write(data, length);
       if (flush)
         usbserial.flush();
+    #elif defined(STM32_I2C_HOST)
+      i2c.WriteI2C(data, length);
     #endif
       break;
     case 3U: