atmega2560/cpu: Fixed wrong using of UART macros

boards/arduino-mega2560/include/periph_conf.h

@@ -131,11 +131,11 @@ extern "C" {
  * @name UART configuration
  * @{
  */
-#define UART_NUMOF          (1U)
+#define UART_NUMOF          (4U)
 #define UART_0_EN           1
-#define UART_1_EN           0
-#define UART_2_EN           0
-#define UART_3_EN           0
+#define UART_1_EN           1
+#define UART_2_EN           1
+#define UART_3_EN           1
 
 /* UART 0 registers */
 #define UART0_CTRL_STAT_A   UCSR0A

cpu/atmega2560/periph/uart.c

@@ -198,7 +198,7 @@ ISR(USART0_RX_vect, ISR_BLOCK)
 ISR(USART1_RX_vect, ISR_BLOCK)
 {
     __enter_isr();
-    config[UART_1].rx_cb(config[UART_1].arg, UART0_DATA_REGISTER);
+    config[UART_1].rx_cb(config[UART_1].arg, UART1_DATA_REGISTER);
 
     if (sched_context_switch_request) {
         thread_yield();
@@ -207,11 +207,11 @@ ISR(USART1_RX_vect, ISR_BLOCK)
 }
 #endif /* UART_1_EN */
 
-#if UART_1_EN
+#if UART_2_EN
 ISR(USART2_RX_vect, ISR_BLOCK)
 {
     __enter_isr();
-    config[UART_2].rx_cb(config[UART_2].arg, UART0_DATA_REGISTER);
+    config[UART_2].rx_cb(config[UART_2].arg, UART2_DATA_REGISTER);
 
     if (sched_context_switch_request) {
         thread_yield();
@@ -220,11 +220,11 @@ ISR(USART2_RX_vect, ISR_BLOCK)
 }
 #endif /* UART_2_EN */
 
-#if UART_2_EN
-ISR(USART2_RX_vect, ISR_BLOCK)
+#if UART_3_EN
+ISR(USART3_RX_vect, ISR_BLOCK)
 {
     __enter_isr();
-    config[UART_3].rx_cb(config[UART_3].arg, UART0_DATA_REGISTER);
+    config[UART_3].rx_cb(config[UART_3].arg, UART3_DATA_REGISTER);
 
     if (sched_context_switch_request) {
         thread_yield();