diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index 7c9e82f7e3..09f8f4f4f0 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -220,7 +220,7 @@ void HardwareSerial::begin(unsigned long baud, byte config)
 
   _serial.baudrate = (uint32_t)baud;
 
-  // Manage databitshardware/arduino/avr/cores/arduino/HardwareSerial.cpp
+  // Manage databits
   switch(config & 0x07) {
     case 0x02:
       databits = 6;
diff --git a/cores/arduino/stm32/uart.c b/cores/arduino/stm32/uart.c
index dd9929abec..10f6acf5d6 100644
--- a/cores/arduino/stm32/uart.c
+++ b/cores/arduino/stm32/uart.c
@@ -58,11 +58,18 @@
 // linked to PIN_SERIAL_TX
 #if !defined(DEBUG_UART)
 #if defined(PIN_SERIAL_TX)
-#define DEBUG_UART pinmap_peripheral(digitalPinToPinName(PIN_SERIAL_TX), PinMap_UART_TX)
+#define DEBUG_UART          pinmap_peripheral(digitalPinToPinName(PIN_SERIAL_TX), PinMap_UART_TX)
+#define DEBUG_PINNAME_TX    digitalPinToPinName(PIN_SERIAL_TX)
 #else
-#define DEBUG_UART NP
+// No debug UART defined
+#define DEBUG_UART          NP
+#define DEBUG_PINNAME_TX    NC
 #endif
 #endif
+#if !defined(DEBUG_UART_BAUDRATE)
+#define DEBUG_UART_BAUDRATE 9600
+#endif
+
 // @brief uart caracteristics
 #if defined(STM32F4xx)
 #define UART_NUM (10)
@@ -83,6 +90,8 @@ static serial_t *rx_callback_obj[UART_NUM];
 static int (*tx_callback[UART_NUM])(serial_t*);
 static serial_t *tx_callback_obj[UART_NUM];
 
+static serial_t serial_debug = { .uart=NP, .index=UART_NUM };
+
 /**
   * @brief  Function called to initialize the uart interface
   * @param  obj : pointer to serial_t structure
@@ -97,6 +106,7 @@ void uart_init(serial_t *obj)
   UART_HandleTypeDef *huart = &(obj->handle);
   GPIO_InitTypeDef GPIO_InitStruct;
   GPIO_TypeDef *port;
+  uint32_t function = (uint32_t)NC;
 
   // Determine the UART to use (UART_1, UART_2, ...)
   USART_TypeDef *uart_tx = pinmap_peripheral(obj->pin_tx, PinMap_UART_TX);
@@ -238,27 +248,29 @@ void uart_init(serial_t *obj)
   //Configure GPIOs
   //RX
   port = set_GPIO_Port_Clock(STM_PORT(obj->pin_rx));
+  function = pinmap_function(obj->pin_rx, PinMap_UART_RX);
   GPIO_InitStruct.Pin         = STM_GPIO_PIN(obj->pin_rx);
-  GPIO_InitStruct.Mode        = STM_PIN_MODE(pinmap_function(obj->pin_rx,PinMap_UART_RX));
+  GPIO_InitStruct.Mode        = STM_PIN_MODE(function);
   GPIO_InitStruct.Speed       = GPIO_SPEED_FREQ_HIGH;
-  GPIO_InitStruct.Pull        = STM_PIN_PUPD(pinmap_function(obj->pin_rx,PinMap_UART_RX));
+  GPIO_InitStruct.Pull        = STM_PIN_PUPD(function);
 #ifdef STM32F1xx
-  pin_SetF1AFPin(STM_PIN_AFNUM(pinmap_function(obj->pin_rx,PinMap_UART_RX)));
+  pin_SetF1AFPin(STM_PIN_AFNUM(function));
 #else
-  GPIO_InitStruct.Alternate   = STM_PIN_AFNUM(pinmap_function(obj->pin_rx,PinMap_UART_RX));
+  GPIO_InitStruct.Alternate   = STM_PIN_AFNUM(function);
 #endif /* STM32F1xx */
   HAL_GPIO_Init(port, &GPIO_InitStruct);
 
   //TX
   port = set_GPIO_Port_Clock(STM_PORT(obj->pin_tx));
+  function = pinmap_function(obj->pin_tx, PinMap_UART_TX);
   GPIO_InitStruct.Pin         = STM_GPIO_PIN(obj->pin_tx);
-  GPIO_InitStruct.Mode        = STM_PIN_MODE(pinmap_function(obj->pin_tx,PinMap_UART_TX));
+  GPIO_InitStruct.Mode        = STM_PIN_MODE(function);
   GPIO_InitStruct.Speed       = GPIO_SPEED_FREQ_HIGH;
-  GPIO_InitStruct.Pull        = STM_PIN_PUPD(pinmap_function(obj->pin_tx,PinMap_UART_TX));
+  GPIO_InitStruct.Pull        = STM_PIN_PUPD(function);
 #ifdef STM32F1xx
-  pin_SetF1AFPin(STM_PIN_AFNUM(pinmap_function(obj->pin_tx,PinMap_UART_TX)));
+  pin_SetF1AFPin(STM_PIN_AFNUM(function));
 #else
-  GPIO_InitStruct.Alternate   = STM_PIN_AFNUM(pinmap_function(obj->pin_tx,PinMap_UART_TX));
+  GPIO_InitStruct.Alternate   = STM_PIN_AFNUM(function);
 #endif /* STM32F1xx */
   HAL_GPIO_Init(port, &GPIO_InitStruct);
 
@@ -399,9 +411,33 @@ size_t uart_write(serial_t *obj, uint8_t data, uint16_t size)
   }
 }
 
+/**
+  * @brief  Function called to initialize the debug uart interface
+  * @note   Call only if debug U(S)ART peripheral is not already initialized
+  *         by a Serial instance
+  *         Default config: 8N1
+  * @retval None
+  */
+void uart_debug_init(void)
+{
+  if ( DEBUG_UART != NP) {
+    serial_debug.pin_rx = pinmap_pin(DEBUG_UART, PinMap_UART_RX);
+#if defined(DEBUG_PINNAME_TX)
+    serial_debug.pin_tx = DEBUG_PINNAME_TX;
+#else
+    serial_debug.pin_tx = pinmap_pin(DEBUG_UART, PinMap_UART_TX);
+#endif
+    serial_debug.baudrate = DEBUG_UART_BAUDRATE;
+    serial_debug.parity = UART_PARITY_NONE;
+    serial_debug.databits = UART_WORDLENGTH_8B;
+    serial_debug.stopbits = UART_STOPBITS_1;
+
+    uart_init(&serial_debug);
+  }
+}
+
 /**
   * @brief  write the data on the uart: used by printf for debug only (syscalls)
-  * @param  obj : pointer to serial_t structure
   * @param  data : bytes to write
   * @param  size : number of data to write
   * @retval The number of bytes written
@@ -409,18 +445,29 @@ size_t uart_write(serial_t *obj, uint8_t data, uint16_t size)
 size_t uart_debug_write(uint8_t *data, uint32_t size)
 {
   uint8_t index = 0;
-  USART_TypeDef* dbg_uart = DEBUG_UART;
   uint32_t tickstart = HAL_GetTick();
+
+  if (DEBUG_UART == NP) {
+    return 0;
+  }
+  /* Search if DEBUG_UART already initialized */
   for(index = 0; index < UART_NUM; index++) {
     if(uart_handlers[index] != NULL) {
-      if(dbg_uart == uart_handlers[index]->Instance) {
+      if(DEBUG_UART == uart_handlers[index]->Instance) {
         break;
       }
     }
   }
 
   if(index >= UART_NUM) {
-    return 0;
+    /* DEBUG_UART not initialized */
+    if( serial_debug.index >= UART_NUM ) {
+      uart_debug_init();
+      if( serial_debug.index >= UART_NUM ) {
+        return 0;
+      }
+    }
+    index = serial_debug.index;
   }
 
   while(HAL_UART_Transmit(uart_handlers[index], data, size, TX_TIMEOUT) != HAL_OK) {
diff --git a/variants/board_template/variant.h b/variants/board_template/variant.h
index 560b6b4111..06255ed24d 100644
--- a/variants/board_template/variant.h
+++ b/variants/board_template/variant.h
@@ -109,6 +109,10 @@ enum {
 #define SERIAL_UART_INSTANCE    x //ex: 2 for Serial2 (USART2)
 // DEBUG_UART could be redefined to print on another instance than 'Serial'
 //#define DEBUG_UART              ((USART_TypeDef *) U(S)ARTX) // ex: USART3
+// DEBUG_UART baudrate, default: 9600 if not defined
+//#define DEBUG_UART_BAUDRATE     x
+// DEBUG_UART Tx pin name, default: the first one found in PinMap_UART_TX for DEBUG_UART
+//#define DEBUG_PINNAME_TX        PX_n // PinName used for TX
 
 // UART Emulation (uncomment if needed, required TIM1)
 //#define UART_EMUL_RX            PX_n // PinName used for RX