diff --git a/components/freemodbus/port/porttimer.c b/components/freemodbus/port/porttimer.c
index c68e171..a98a5d2 100644
--- a/components/freemodbus/port/porttimer.c
+++ b/components/freemodbus/port/porttimer.c
@@ -50,6 +50,7 @@
 #include "mbport.h"
 #include "driver/timer.h"
 #include "port_serial_slave.h"
+#include "sdkconfig.h"
 
 #ifdef CONFIG_FMB_TIMER_PORT_ENABLED
 
@@ -63,6 +64,7 @@
 
 static const USHORT usTimerIndex = CONFIG_FMB_TIMER_INDEX; // Modbus Timer index used by stack
 static const USHORT usTimerGroupIndex = CONFIG_FMB_TIMER_GROUP; // Modbus Timer group index used by stack
+static timer_isr_handle_t xTimerIntHandle;                      // Timer interrupt handle
 
 static timg_dev_t *MB_TG[2] = {&TIMERG0, &TIMERG1};
 
@@ -121,7 +123,8 @@ BOOL xMBPortTimersInit(USHORT usTim1Timerout50us)
                     "failure to set alarm failure, timer_set_alarm_value() returned (0x%x).",
                     (uint32_t)xErr);
     // Register ISR for timer
-    xErr = timer_isr_register(usTimerGroupIndex, usTimerIndex, vTimerGroupIsr, (void*)(uint32_t)usTimerIndex, ESP_INTR_FLAG_IRAM, NULL);
+    xErr = timer_isr_register(usTimerGroupIndex, usTimerIndex, vTimerGroupIsr,
+                                (void*)(uint32_t)usTimerIndex, ESP_INTR_FLAG_LOWMED, &xTimerIntHandle);
     MB_PORT_CHECK((xErr == ESP_OK), FALSE,
                     "timer set value failure, timer_isr_register() returned (0x%x).",
                     (uint32_t)xErr);
@@ -154,6 +157,6 @@ void vMBPortTimerClose(void)
 #ifdef CONFIG_FMB_TIMER_PORT_ENABLED
     ESP_ERROR_CHECK(timer_pause(usTimerGroupIndex, usTimerIndex));
     ESP_ERROR_CHECK(timer_disable_intr(usTimerGroupIndex, usTimerIndex));
+    ESP_ERROR_CHECK(esp_intr_free(xTimerIntHandle));
 #endif
 }
-
diff --git a/components/freemodbus/port/porttimer_m.c b/components/freemodbus/port/porttimer_m.c
index 55c561c..b2e1723 100644
--- a/components/freemodbus/port/porttimer_m.c
+++ b/components/freemodbus/port/porttimer_m.c
@@ -51,16 +51,15 @@
 #define MB_TIMER_WITH_RELOAD    (1)
 
 // Timer group and timer number to measure time (configurable in KConfig)
-#define MB_TIMER_INDEX CONFIG_FMB_TIMER_INDEX
-#define MB_TIMER_GROUP CONFIG_FMB_TIMER_GROUP
-
-#define MB_TIMER_IO_LED 0
+#define MB_TIMER_INDEX          (CONFIG_FMB_TIMER_INDEX)
+#define MB_TIMER_GROUP          (CONFIG_FMB_TIMER_GROUP)
 
 /* ----------------------- Variables ----------------------------------------*/
 static USHORT usT35TimeOut50us;
 
 static const USHORT usTimerIndex = MB_TIMER_INDEX;      // Initialize Modbus Timer index used by stack,
 static const USHORT usTimerGroupIndex = MB_TIMER_GROUP; // Timer group index used by stack
+static timer_isr_handle_t xTimerIntHandle;              // Timer interrupt handle
 
 static timg_dev_t *MB_TG[2] = { &TIMERG0, &TIMERG1 };
 
@@ -128,7 +127,7 @@ BOOL xMBMasterPortTimersInit(USHORT usTimeOut50us)
                     (uint32_t)xErr);
     // Register ISR for timer
     xErr = timer_isr_register(usTimerGroupIndex, usTimerIndex,
-                                vTimerGroupIsr, (void*)(uint32_t)usTimerIndex, ESP_INTR_FLAG_IRAM, NULL);
+                                vTimerGroupIsr, (void*)(uint32_t)usTimerIndex, ESP_INTR_FLAG_LOWMED, &xTimerIntHandle);
     MB_PORT_CHECK((xErr == ESP_OK), FALSE,
                     "timer set value failure, timer_isr_register() returned (0x%x).",
                     (uint32_t)xErr);
@@ -164,7 +163,7 @@ static BOOL xMBMasterPortTimersEnable(USHORT usTimerTics50us)
     MB_PORT_CHECK((xErr == ESP_OK), FALSE,
                             "timer start failure, timer_start() returned (0x%x).",
                             (uint32_t)xErr);
-    //ESP_LOGD(MB_PORT_TAG,"%s Init timer.", __func__);
+    ESP_LOGD(MB_PORT_TAG,"%s Init timer.", __func__);
     return TRUE;
 }
 
@@ -211,4 +210,5 @@ void vMBMasterPortTimerClose(void)
 {
     ESP_ERROR_CHECK(timer_pause(usTimerGroupIndex, usTimerIndex));
     ESP_ERROR_CHECK(timer_disable_intr(usTimerGroupIndex, usTimerIndex));
-}
+    ESP_ERROR_CHECK(esp_intr_free(xTimerIntHandle));
+}
\ No newline at end of file
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 30aae20..b162312 100644
--- a/components/freemodbus/serial_master/modbus_controller/mbc_serial_master.c
+++ b/components/freemodbus/serial_master/modbus_controller/mbc_serial_master.c
@@ -140,6 +140,7 @@ static esp_err_t mbc_serial_master_destroy(void)
     MB_MASTER_CHECK((mb_error == MB_ENOERR), ESP_ERR_INVALID_STATE,
             "mb stack close failure returned (0x%x).", (uint32_t)mb_error);
     free(mbm_interface_ptr); // free the memory allocated for options
+    mbm_interface_ptr = NULL;
     return ESP_OK;
 }
 
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 5c6b05f..6a125d9 100644
--- a/components/freemodbus/serial_slave/modbus_controller/mbc_serial_slave.c
+++ b/components/freemodbus/serial_slave/modbus_controller/mbc_serial_slave.c
@@ -133,7 +133,7 @@ static esp_err_t mbc_serial_slave_destroy(void)
     MB_SLAVE_CHECK((mb_error == MB_ENOERR), ESP_ERR_INVALID_STATE,
             "mb stack close failure returned (0x%x).", (uint32_t)mb_error);
     free(mbs_interface_ptr);
-
+    mbs_interface_ptr = NULL;
     return ESP_OK;
 }