🐛 Fix UART pins for GD32 MFL (#28011)

Author: ellensp

Marlin/src/inc/Conditionals-4-adv.h

@@ -1486,7 +1486,7 @@
   #if MB(MKS_MONSTER8_V1, BTT_SKR_MINI_E3_V1_0, BTT_SKR_MINI_E3_V1_2, BTT_SKR_MINI_E3_V2_0, BTT_SKR_MINI_E3_V3_0, BTT_SKR_MINI_E3_V3_0_1, BTT_SKR_E3_TURBO, BTT_OCTOPUS_V1_1, BTT_SKR_V3_0, BTT_SKR_V3_0_EZ, AQUILA_V101)
 
     #define LCD_SERIAL_PORT 1
-  #elif MB(CREALITY_V24S1_301, CREALITY_V24S1_301F4, CREALITY_F401RE, CREALITY_V423, CREALITY_CR4NTXXC10, CREALITY_CR4NS, MKS_ROBIN, PANOWIN_CUTLASS, KODAMA_BARDO)
+  #elif MB(CREALITY_V24S1_301, CREALITY_V24S1_301F4, CREALITY_F401RE, CREALITY_V422_GD32_MFL, CREALITY_V423, CREALITY_V427_GD32_MFL, CREALITY_CR4NTXXC10, CREALITY_CR4NS, MKS_ROBIN, PANOWIN_CUTLASS, KODAMA_BARDO)
     #define LCD_SERIAL_PORT 2
   #else
     #define LCD_SERIAL_PORT 3

Marlin/src/pins/stm32f1/pins_CREALITY_V4.h

@@ -326,13 +326,26 @@
 // Changing these will not change the pin they are on.
 
 // Hardware UART pins
-#define UART1_TX_PIN                        PA9   // default uses CH340 RX
-#define UART1_RX_PIN                        PA10  // default uses CH340 TX
-#define UART2_TX_PIN                        PA2   // default uses HEATER_BED_PIN
-#define UART2_RX_PIN                        PA3   // not connected
-#define UART3_TX_PIN                        PB10  // default uses LCD connector
-#define UART3_RX_PIN                        PB11  // default uses LCD connector
-#define UART4_TX_PIN                        PC10  // default uses sdcard SDIO_D2
-#define UART4_RX_PIN                        PC11  // default uses sdcard SDIO_D3
-#define UART5_TX_PIN                        PC12  // default uses sdcard SDIO_CK
-#define UART5_RX_PIN                        PD2   // default uses sdcard SDIO_CMD
+#ifdef ARDUINO_ARCH_MFL                           // GD32 MFL UARTs start from 0
+  #define UART0_TX_PIN                      PA9   // default uses CH340 RX
+  #define UART0_RX_PIN                      PA10  // default uses CH340 TX
+  #define UART1_TX_PIN                      PA2   // default uses HEATER_BED_PIN
+  #define UART1_RX_PIN                      PA3   // not connected
+  #define UART2_TX_PIN                      PB10  // default uses LCD connector
+  #define UART2_RX_PIN                      PB11  // default uses LCD connector
+  #define UART3_TX_PIN                      PC10  // default uses sdcard SDIO_D2
+  #define UART3_RX_PIN                      PC11  // default uses sdcard SDIO_D3
+  #define UART4_TX_PIN                      PC12  // default uses sdcard SDIO_CK
+  #define UART4_RX_PIN                      PD2   // default uses sdcard SDIO_CMD
+#else
+  #define UART1_TX_PIN                      PA9   // default uses CH340 RX
+  #define UART1_RX_PIN                      PA10  // default uses CH340 TX
+  #define UART2_TX_PIN                      PA2   // default uses HEATER_BED_PIN
+  #define UART2_RX_PIN                      PA3   // not connected
+  #define UART3_TX_PIN                      PB10  // default uses LCD connector
+  #define UART3_RX_PIN                      PB11  // default uses LCD connector
+  #define UART4_TX_PIN                      PC10  // default uses sdcard SDIO_D2
+  #define UART4_RX_PIN                      PC11  // default uses sdcard SDIO_D3
+  #define UART5_TX_PIN                      PC12  // default uses sdcard SDIO_CK
+  #define UART5_RX_PIN                      PD2   // default uses sdcard SDIO_CMD
+#endif