l475 disco: Move st-link uart rx/tx settings into variant.cpp

STM32/boards.txt

@@ -757,6 +757,7 @@ DISCOVERY_F746NG.menu.serial.SerialUSB.build.extra_flags_serial=-DMENU_SERIAL=Se
 DISCO_B_L475E_IOT01A.name=Discovery B-L475E-IOT01A
 DISCO_B_L475E_IOT01A.upload.maximum_size=1048576
 DISCO_B_L475E_IOT01A.upload.maximum_data_size=131072
+DISCO_B_L475E_IOT01A.build.core=arduino
 DISCO_B_L475E_IOT01A.build.mcu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard
 DISCO_B_L475E_IOT01A.build.series=STM32L4
 DISCO_B_L475E_IOT01A.build.variant=DISCO_B_L475E_IOT01A

STM32/libraries/BoardExamples/examples/B-L475E-IOT01A/Serial_Print/Serial_Print.ino

@@ -1,8 +1,6 @@
 // Print milliseconds to Serial monitor every second
 
 void setup() {
-  SerialUART1.stm32SetTX(PB6);
-  SerialUART1.stm32SetRX(PB7);
   SerialUART1.begin(115200); 
 }
 

STM32/libraries/BoardExamples/examples/B-L475E-IOT01A/Serial_Read/Serial_Read.ino

@@ -7,8 +7,6 @@ int incomingByte;      // variable to save incoming serial data
 
 void setup() {
   // initialize SerialUART1 communication:
-  SerialUART1.stm32SetTX(PB6);
-  SerialUART1.stm32SetRX(PB7);
   SerialUART1.begin(115200);
   
   // initialize the LED pin as an output:

STM32/variants/DISCO_B_L475E_IOT01A/variant.cpp

@@ -1,7 +1,9 @@
 #include "stm32_build_defines.h"
 #include "stm32_def.h"
 
-extern void SystemClock_Config(void) {
+#include "Arduino.h"
+
+extern "C" void SystemClock_Config(void) {
   RCC_OscInitTypeDef RCC_OscInitStruct;
   RCC_ClkInitTypeDef RCC_ClkInitStruct;
 
@@ -38,3 +40,9 @@ extern void SystemClock_Config(void) {
   HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
   
 }
+
+extern "C" void initVariant() {
+    //UART1 is connected to ST-Link V2.1 as Virtual Com port on non-default PA9/PB7 pins
+    SerialUART1.stm32SetTX(PA9);
+    SerialUART1.stm32SetRX(PB7);
+}