diff --git a/config/arch/cortexM4_stm32f4/stm32f407vg_stm32f4discovery/board_settings.h b/config/arch/cortexM4_stm32f4/stm32f407vg_stm32f4discovery/board_settings.h
index 6f8a1da27f325df7045549b248ddfdd093d22dcf..6d9ea0eb8f6a453bad57cf3ff3fce6690fb85883 100644
--- a/config/arch/cortexM4_stm32f4/stm32f407vg_stm32f4discovery/board_settings.h
+++ b/config/arch/cortexM4_stm32f4/stm32f407vg_stm32f4discovery/board_settings.h
@@ -62,10 +62,15 @@ const unsigned int TICK_FREQ=1000;
 const unsigned int AUX_TIMER_CLOCK=100000;
 const unsigned int AUX_TIMER_MAX=0xffff; ///<\internal Aux timer is 16 bits
 
-/// Serial port
+/// Serial port (USART3 PB10=TX, PB11=RX)
 const unsigned int defaultSerial=3;
 const unsigned int defaultSerialSpeed=19200;
 const bool defaultSerialFlowctrl=false;
+// Aux serial port (hardcoded USART2 PA2=TX, PA3=RX).
+// Uncomment AUX_SERIAL to enable. The device will appear as /dev/auxtty.
+#define AUX_SERIAL "auxtty"
+const unsigned int auxSerialSpeed=9600;
+const bool auxSerialFlowctrl=false;
 //#define SERIAL_1_DMA //Serial 1 is not used, so not enabling DMA
 //#define SERIAL_2_DMA //Serial 2 DMA conflicts with I2S driver in the examples
 #define SERIAL_3_DMA