diff --git a/components/freemodbus/common/include/esp_modbus_common.h b/components/freemodbus/common/include/esp_modbus_common.h
index 7bec024..34810cf 100644
--- a/components/freemodbus/common/include/esp_modbus_common.h
+++ b/components/freemodbus/common/include/esp_modbus_common.h
@@ -22,10 +22,10 @@
 #define MB_CONTROLLER_PRIORITY              (CONFIG_FMB_SERIAL_TASK_PRIO - 1)    // priority of MB controller task
 
 // Default port defines
-#define MB_DEVICE_ADDRESS   (1)             // Default slave device address in Modbus
-#define MB_DEVICE_SPEED     (115200)        // Default Modbus speed for now hard defined
-#define MB_UART_PORT        (UART_NUM_2)    // Default UART port number
-#define MB_PAR_INFO_TOUT    (10)            // Timeout for get parameter info
+#define MB_DEVICE_ADDRESS   (1)                 // Default slave device address in Modbus
+#define MB_DEVICE_SPEED     (115200)            // Default Modbus speed for now hard defined
+#define MB_UART_PORT        (UART_NUM_MAX - 1)  // Default UART port number
+#define MB_PAR_INFO_TOUT    (10)                // Timeout for get parameter info
 #define MB_PARITY_NONE      (UART_PARITY_DISABLE)
 
 // The Macros below handle the endianness while transfer N byte data into buffer
diff --git a/components/freemodbus/port/portserial.c b/components/freemodbus/port/portserial.c
index 54bbe83..10967af 100644
--- a/components/freemodbus/port/portserial.c
+++ b/components/freemodbus/port/portserial.c
@@ -78,7 +78,7 @@ static TaskHandle_t  xMbTaskHandle;
 static const CHAR *TAG = "MB_SERIAL";
 
 // The UART hardware port number
-static UCHAR ucUartNumber = UART_NUM_2;
+static UCHAR ucUartNumber = UART_NUM_MAX - 1;
 
 static BOOL bRxStateEnabled = FALSE; // Receiver enabled flag
 static BOOL bTxStateEnabled = FALSE; // Transmitter enabled flag
diff --git a/components/freemodbus/port/portserial_m.c b/components/freemodbus/port/portserial_m.c
index 74a4a1b..3302691 100644
--- a/components/freemodbus/port/portserial_m.c
+++ b/components/freemodbus/port/portserial_m.c
@@ -73,7 +73,7 @@ static QueueHandle_t xMbUartQueue;
 static TaskHandle_t  xMbTaskHandle;
 
 // The UART hardware port number
-static UCHAR ucUartNumber = UART_NUM_2;
+static UCHAR ucUartNumber = UART_NUM_MAX - 1;
 
 static BOOL bRxStateEnabled = FALSE; // Receiver enabled flag
 static BOOL bTxStateEnabled = FALSE; // Transmitter enabled flag
diff --git a/components/freemodbus/serial_master/modbus_controller/mbc_serial_master.c b/components/freemodbus/serial_master/modbus_controller/mbc_serial_master.c
index 8db15ae..30aae20 100644
--- a/components/freemodbus/serial_master/modbus_controller/mbc_serial_master.c
+++ b/components/freemodbus/serial_master/modbus_controller/mbc_serial_master.c
@@ -83,7 +83,7 @@ static esp_err_t mbc_serial_master_setup(void* comm_info)
     MB_MASTER_CHECK(((comm_info_ptr->mode == MB_MODE_RTU) || (comm_info_ptr->mode == MB_MODE_ASCII)),
                 ESP_ERR_INVALID_ARG, "mb incorrect mode = (0x%x).",
                 (uint32_t)comm_info_ptr->mode);
-    MB_MASTER_CHECK((comm_info_ptr->port <= UART_NUM_2), ESP_ERR_INVALID_ARG,
+    MB_MASTER_CHECK((comm_info_ptr->port < UART_NUM_MAX), ESP_ERR_INVALID_ARG,
                 "mb wrong port to set = (0x%x).", (uint32_t)comm_info_ptr->port);
     MB_MASTER_CHECK((comm_info_ptr->parity <= UART_PARITY_EVEN), ESP_ERR_INVALID_ARG,
                 "mb wrong parity option = (0x%x).", (uint32_t)comm_info_ptr->parity);
diff --git a/components/freemodbus/serial_slave/modbus_controller/mbc_serial_slave.c b/components/freemodbus/serial_slave/modbus_controller/mbc_serial_slave.c
index 86e9616..72d753e 100644
--- a/components/freemodbus/serial_slave/modbus_controller/mbc_serial_slave.c
+++ b/components/freemodbus/serial_slave/modbus_controller/mbc_serial_slave.c
@@ -69,7 +69,7 @@ static esp_err_t mbc_serial_slave_setup(void* comm_info)
     MB_SLAVE_CHECK((comm_settings->slave_addr <= MB_ADDRESS_MAX),
                 ESP_ERR_INVALID_ARG, "mb wrong slave address = (0x%x).",
                 (uint32_t)comm_settings->slave_addr);
-    MB_SLAVE_CHECK((comm_settings->port <= UART_NUM_2), ESP_ERR_INVALID_ARG,
+    MB_SLAVE_CHECK((comm_settings->port < UART_NUM_MAX), ESP_ERR_INVALID_ARG,
                 "mb wrong port to set = (0x%x).", (uint32_t)comm_settings->port);
     MB_SLAVE_CHECK((comm_settings->parity <= UART_PARITY_EVEN), ESP_ERR_INVALID_ARG,
                 "mb wrong parity option = (0x%x).", (uint32_t)comm_settings->parity);