diff --git a/DCCTimerSTM32.cpp b/DCCTimerSTM32.cpp
index 4f9cbdd..944f466 100644
--- a/DCCTimerSTM32.cpp
+++ b/DCCTimerSTM32.cpp
@@ -37,16 +37,19 @@ HardwareSerial Serial1(PB7, PA15);  // Rx=PB7, Tx=PA15 -- CN7 pins 17 and 21 - F
 // Serial2 is defined to use USART2 by default, but is in fact used as the diag console
 // via the debugger on the Nucleo-64. It is therefore unavailable for other DCC-EX uses like WiFi, DFPlayer, etc.
 // Let's define Serial6 as an additional serial port (the only other option for the Nucleo-64s)
-HardwareSerial Serial6(PA12, PA11);  // Rx=PA12, Tx=PA11 -- CN10 pins 12 and 14 - F411RE
+HardwareSerial Serial3(PA12, PA11);  // Rx=PA12, Tx=PA11 -- CN10 pins 12 and 14 - F411RE
 #elif defined(ARDUINO_NUCLEO_F446RE)
 // Nucleo-64 boards don't have Serial1 defined by default
-HardwareSerial Serial1(PA10, PB6);  // Rx=PA10 (D2), Tx=PB6 (D10) -- CN10 pins 17 and 9 - F446RE 
+// HardwareSerial Serial1(PA10, PB6);  // Rx=PA10 (D2), Tx=PB6 (D10) -- CN10 pins 17 and 9 - F446RE 
 // Serial2 is defined to use USART2 by default, but is in fact used as the diag console
 // via the debugger on the Nucleo-64. It is therefore unavailable for other DCC-EX uses like WiFi, DFPlayer, etc.
+HardwareSerial Serial1(PC11, PC10);  // Rx=PC11, Tx=PC10 -- USART3 - F446RE
+HardwareSerial Serial3(PD2, PC12);  // Rx=PC7, Tx=PC6 -- UART5 - F446RE
 // NB: USART3 and USART6 are available but as yet undefined
 #elif defined(ARDUINO_NUCLEO_F412ZG) || defined(ARDUINO_NUCLEO_F429ZI) || defined(ARDUINO_NUCLEO_F446ZE)
 // Nucleo-144 boards don't have Serial1 defined by default
-HardwareSerial Serial1(PG9, PG14);  // Rx=PG9, Tx=PG14 -- D0, D1 - F412ZG/F446ZE
+HardwareSerial Serial1(PC11, PC10);  // Rx=PC11, Tx=PC10 -- USART3 - F412ZG/F446ZE
+HardwareSerial Serial3(PD2, PC12);  // Rx=PC7, Tx=PC6 -- UART5 - F412ZG/F446ZE
 // Serial2 is defined to use USART2 by default, but is in fact used as the diag console
 // via the debugger on the Nucleo-144. It is therefore unavailable for other DCC-EX uses like WiFi, DFPlayer, etc.
 // NB:
diff --git a/defines.h b/defines.h
index 5582e8b..3f5c3ba 100644
--- a/defines.h
+++ b/defines.h
@@ -147,7 +147,8 @@
   #ifndef I2C_USE_WIRE
   #define I2C_USE_WIRE
   #endif
-
+  #undef NUM_SERIAL
+  #define NUM_SERIAL 3
 
 /* TODO when ready 
 #elif defined(ARDUINO_ARCH_RP2040)