diff --git a/cpu/sam3/periph/uart.c b/cpu/sam3/periph/uart.c
index 07da80ddd..95c2cad47 100644
--- a/cpu/sam3/periph/uart.c
+++ b/cpu/sam3/periph/uart.c
@@ -28,63 +28,47 @@
 #define ENABLE_DEBUG (0)
 #include "debug.h"
 
-/* guard file in case no UART device was specified */
-#if UART_NUMOF
-
-/**
- * @brief Each UART device has to store two callbacks.
- */
-typedef struct {
-    uart_rx_cb_t rx_cb;
-    uart_tx_cb_t tx_cb;
-    void *arg;
-} uart_conf_t;
-
 /**
  * @brief Allocate memory to store the callback functions.
  */
-static uart_conf_t uart_config[UART_NUMOF];
+static uart_isr_ctx_t uart_config[UART_NUMOF];
 
+static int init_base(uart_t uart, uint32_t baudrate);
 
-int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, uart_tx_cb_t tx_cb, void *arg)
+int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* initialize basic functionality */
-    int res = uart_init_blocking(uart, baudrate);
+    int res = init_base(uart, baudrate);
     if (res != 0) {
         return res;
     }
 
     /* register callbacks */
     uart_config[uart].rx_cb = rx_cb;
-    uart_config[uart].tx_cb = tx_cb;
     uart_config[uart].arg = arg;
 
     /* configure interrupts and enable RX interrupt */
     switch (uart) {
 #if UART_0_EN
         case UART_0:
-            NVIC_SetPriority(UART_0_IRQ, UART_IRQ_PRIO);
             NVIC_EnableIRQ(UART_0_IRQ);
             UART_0_DEV->UART_IER = UART_IER_RXRDY;
             break;
 #endif
 #if UART_1_EN
         case UART_1:
-            NVIC_SetPriority(UART_1_IRQ, UART_IRQ_PRIO);
             NVIC_EnableIRQ(UART_1_IRQ);
             UART_1_DEV->US_IER = US_IER_RXRDY;
             break;
 #endif
 #if UART_2_EN
         case UART_2:
-            NVIC_SetPriority(UART_2_IRQ, UART_IRQ_PRIO);
             NVIC_EnableIRQ(UART_2_IRQ);
             UART_2_DEV->US_IER = US_IER_RXRDY;
             break;
 #endif
 #if UART_3_EN
         case UART_3:
-            NVIC_SetPriority(UART_3_IRQ, UART_IRQ_PRIO);
             NVIC_EnableIRQ(UART_3_IRQ);
             UART_3_DEV->US_IER = US_IER_RXRDY;
             break;
@@ -93,7 +77,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, uart_tx_cb_t t
     return 0;
 }
 
-int uart_init_blocking(uart_t uart, uint32_t baudrate)
+static int init_base(uart_t uart, uint32_t baudrate)
 {
     switch (uart) {
 #if UART_0_EN
@@ -168,120 +152,39 @@ int uart_init_blocking(uart_t uart, uint32_t baudrate)
     return 0;
 }
 
-void uart_tx_begin(uart_t uart)
+void uart_write(uart_t uart, const uint8_t *data, size_t len)
 {
-    switch (uart) {
-#if UART_0_EN
-        case UART_0:
-            UART_0_DEV->UART_IER = UART_IER_TXRDY;
-            break;
-#endif
-#if UART_1_EN
-        case UART_1:
-            UART_1_DEV->US_IER = US_IER_TXRDY;
-            break;
-#endif
-#if UART_2_EN
-        case UART_2:
-            UART_2_DEV->US_IER = US_IER_TXRDY;
-            break;
-#endif
-#if UART_3_EN
-        case UART_3:
-            UART_3_DEV->US_IER = US_IER_TXRDY;
-            break;
-#endif
-    }
-}
-
-int uart_write(uart_t uart, char data)
-{
-    switch (uart) {
-#if UART_0_EN
-        case UART_0:
-            UART_0_DEV->UART_THR = data;
-            break;
-#endif
-#if UART_1_EN
-        case UART_1:
-            UART_1_DEV->US_THR = data;
-            break;
-#endif
-#if UART_2_EN
-        case UART_2:
-            UART_2_DEV->US_THR = data;
-            break;
-#endif
-#if UART_3_EN
-        case UART_3:
-            UART_3_DEV->US_THR = data;
-            break;
-#endif
-    }
-    return 1;
-}
+    Uart *dev;
 
-int uart_read_blocking(uart_t uart, char *data)
-{
     switch (uart) {
 #if UART_0_EN
         case UART_0:
-            while (!(UART_0_DEV->UART_SR & UART_SR_RXRDY));
-            *data = (char)UART_0_DEV->UART_RHR;
+            dev = (Uart *)UART_0_DEV;
             break;
 #endif
 #if UART_1_EN
         case UART_1:
-            while (!(UART_1_DEV->US_CSR & US_CSR_RXRDY));
-            *data = (char)UART_1_DEV->US_RHR;
+            dev = (Uart *)UART_1_DEV;
             break;
 #endif
 #if UART_2_EN
         case UART_2:
-            while (!(UART_2_DEV->US_CSR & US_CSR_RXRDY));
-            *data = (char)UART_2_DEV->US_RHR;
+            dev = (Uart *)UART_2_DEV;
             break;
 #endif
 #if UART_3_EN
         case UART_3:
-            while (!(UART_3_DEV->US_CSR & US_CSR_RXRDY));
-            *data = (char)UART_3_DEV->US_RHR;
+            dev = (Uart *)UART_3_DEV;
             break;
 #endif
+        default:
+            return;
     }
 
-    return 1;
-}
-
-int uart_write_blocking(uart_t uart, char data)
-{
-    switch (uart) {
-#if UART_0_EN
-        case UART_0:
-            while (!(UART_0_DEV->UART_SR & UART_SR_TXRDY));
-            UART_0_DEV->UART_THR = data;
-            break;
-#endif
-#if UART_1_EN
-        case UART_1:
-            while(!(UART_1_DEV->US_CSR & US_CSR_TXRDY));
-            UART_1_DEV->US_THR = data;
-            break;
-#endif
-#if UART_2_EN
-        case UART_2:
-            while(!(UART_2_DEV->US_CSR & US_CSR_TXRDY));
-            UART_2_DEV->US_THR = data;
-            break;
-#endif
-#if UART_3_EN
-        case UART_3:
-            while(!(UART_3_DEV->US_CSR & US_CSR_TXRDY));
-            UART_3_DEV->US_THR = data;
-            break;
-#endif
+    for (size_t i = 0; i < len; i++) {
+        while (!(dev->UART_SR & UART_SR_TXRDY));
+        dev->UART_THR = data[i];
     }
-    return 1;
 }
 
 void uart_poweron(uart_t uart)
@@ -343,11 +246,6 @@ void UART_0_ISR(void)
         char data = (char)UART_0_DEV->UART_RHR;
         uart_config[UART_0].rx_cb(uart_config[UART_0].arg, data);
     }
-    if ((UART_0_DEV->UART_SR & UART_SR_TXRDY) && (UART_0_DEV->UART_IMR & UART_IMR_TXRDY)) {
-        if (uart_config[UART_0].tx_cb(uart_config[UART_0].arg) == 0) {
-            UART_0_DEV->UART_IDR = UART_IDR_TXRDY;
-        }
-    }
     if (sched_context_switch_request) {
         thread_yield();
     }
@@ -361,11 +259,6 @@ void UART_1_ISR(void)
         char data = (char)UART_1_DEV->US_RHR;
         uart_config[UART_1].rx_cb(uart_config[UART_1].arg, data);
     }
-    if ((UART_1_DEV->US_CSR & US_CSR_TXRDY) && (UART_1_DEV->US_IMR & US_IMR_TXRDY)) {
-        if (uart_config[UART_1].tx_cb(uart_config[UART_1].arg) == 0) {
-            UART_1_DEV->US_IDR = US_IDR_TXRDY;
-        }
-    }
     if (sched_context_switch_request) {
         thread_yield();
     }
@@ -379,11 +272,6 @@ void UART_2_ISR(void)
         char data = (char)UART_2_DEV->US_RHR;
         uart_config[UART_2].rx_cb(uart_config[UART_2].arg, data);
     }
-    if ((UART_2_DEV->US_CSR & US_CSR_TXRDY) && (UART_2_DEV->US_IMR & US_IMR_TXRDY)) {
-        if (uart_config[UART_2].tx_cb(uart_config[UART_2].arg) == 0) {
-            UART_2_DEV->US_IDR = US_IDR_TXRDY;
-        }
-    }
     if (sched_context_switch_request) {
         thread_yield();
     }
@@ -397,15 +285,8 @@ void UART_3_ISR(void)
         char data = (char)UART_3_DEV->US_RHR;
         uart_config[UART_3].rx_cb(uart_config[UART_3].arg, data);
     }
-    if ((UART_3_DEV->US_CSR & US_CSR_TXRDY) && (UART_3_DEV->US_IMR & US_IMR_TXRDY)) {
-        if (uart_config[UART_3].tx_cb(uart_config[UART_3].arg) == 0) {
-            UART_3_DEV->US_IDR = US_IDR_TXRDY;
-        }
-    }
     if (sched_context_switch_request) {
         thread_yield();
     }
 }
 #endif
-
-#endif /* UART_NUMOF */