diff --git a/components/freemodbus/port/port.h b/components/freemodbus/port/port.h
index 06d7a28c79..5307f371fc 100644
--- a/components/freemodbus/port/port.h
+++ b/components/freemodbus/port/port.h
@@ -37,7 +37,7 @@
 #define MB_SERIAL_BUF_SIZE          (CONFIG_FMB_SERIAL_BUF_SIZE)
 
 // common definitions for serial port implementations
-#define MB_SERIAL_TX_TOUT_MS        (100)
+#define MB_SERIAL_TX_TOUT_MS        (2200) // maximum time for transmission of longest allowed frame buffer
 #define MB_SERIAL_TX_TOUT_TICKS     pdMS_TO_TICKS(MB_SERIAL_TX_TOUT_MS) // timeout for transmission
 #define MB_SERIAL_RX_TOUT_MS        (1)
 #define MB_SERIAL_RX_TOUT_TICKS     pdMS_TO_TICKS(MB_SERIAL_RX_TOUT_MS) // timeout for receive
diff --git a/components/freemodbus/port/portserial.c b/components/freemodbus/port/portserial.c
index ed77fe2d1a..9218ccb382 100644
--- a/components/freemodbus/port/portserial.c
+++ b/components/freemodbus/port/portserial.c
@@ -119,7 +119,7 @@ BOOL xMBPortSerialTxPoll(void)
         }
         ESP_LOGD(TAG, "MB_TX_buffer send: (%d) bytes\n", (uint16_t)usCount);
         // Waits while UART sending the packet
-        esp_err_t xTxStatus = uart_wait_tx_idle_polling(ucUartNumber);
+        esp_err_t xTxStatus = uart_wait_tx_done(ucUartNumber, MB_SERIAL_TX_TOUT_TICKS);
         vMBPortSerialEnable(TRUE, FALSE);
         MB_PORT_CHECK((xTxStatus == ESP_OK), FALSE, "mb serial sent buffer failure.");
         return TRUE;
diff --git a/components/freemodbus/port/portserial_m.c b/components/freemodbus/port/portserial_m.c
index 7ae8bfc9c9..1ab6ae7f3c 100644
--- a/components/freemodbus/port/portserial_m.c
+++ b/components/freemodbus/port/portserial_m.c
@@ -113,7 +113,7 @@ BOOL xMBMasterPortSerialTxPoll(void)
         }
         ESP_LOGD(TAG, "MB_TX_buffer sent: (%d) bytes.", (uint16_t)(usCount - 1));
         // Waits while UART sending the packet
-        esp_err_t xTxStatus = uart_wait_tx_idle_polling(ucUartNumber);
+        esp_err_t xTxStatus = uart_wait_tx_done(ucUartNumber, MB_SERIAL_TX_TOUT_TICKS);
         vMBMasterPortSerialEnable(TRUE, FALSE);
         MB_PORT_CHECK((xTxStatus == ESP_OK), FALSE, "mb serial sent buffer failure.");
         return TRUE;