diff --git a/cpu/atmega_common/periph/uart.c b/cpu/atmega_common/periph/uart.c
index 2d3bd52d00..4449ab2bf6 100644
--- a/cpu/atmega_common/periph/uart.c
+++ b/cpu/atmega_common/periph/uart.c
@@ -114,7 +114,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* make sure the given device is valid */
     if (uart >= UART_NUMOF) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* register interrupt context */
@@ -132,7 +132,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     /* enable RX and TX and the RX interrupt */
     dev[uart]->CSRB = ((1 << RXCIE0) | (1 << RXEN0) | (1 << TXEN0));
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/cc2538/periph/uart.c b/cpu/cc2538/periph/uart.c
index ac8a99db84..4c1a0b7bf4 100644
--- a/cpu/cc2538/periph/uart.c
+++ b/cpu/cc2538/periph/uart.c
@@ -160,8 +160,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* initialize basic functionality */
     int res = init_base(uart, baudrate);
-
-    if (res != 0) {
+    if (res != UART_OK) {
         return res;
     }
 
@@ -183,9 +182,11 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
             NVIC_EnableIRQ(UART1_IRQn);
             break;
 #endif
+        default:
+            return UART_NODEV;
     }
 
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -240,7 +241,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
 
         default:
             (void)u;
-            return -1;
+            return UART_NODEV;
     }
 
 #if UART_0_EN || UART_1_EN
@@ -313,7 +314,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
     /* UART Enable */
     u->cc2538_uart_ctl.CTLbits.UARTEN = 1;
 
-    return 0;
+    return UART_OK;
 #endif /* UART_0_EN || UART_1_EN */
 }
 
diff --git a/cpu/cc26x0/periph/uart.c b/cpu/cc26x0/periph/uart.c
index dd4607497d..de67b49514 100644
--- a/cpu/cc26x0/periph/uart.c
+++ b/cpu/cc26x0/periph/uart.c
@@ -49,7 +49,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* make sure the uart device is valid */
     if (uart != 0) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* enable clocks: serial power domain and UART */
@@ -89,7 +89,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     /* start the UART */
     UART->CTL = ENABLE_MASK;
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/ezr32wg/periph/uart.c b/cpu/ezr32wg/periph/uart.c
index 1fea3e37a0..3179c6ba79 100644
--- a/cpu/ezr32wg/periph/uart.c
+++ b/cpu/ezr32wg/periph/uart.c
@@ -48,7 +48,7 @@ int uart_init(uart_t dev, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 
     /* check if device is valid and get base register address */
     if (dev >= UART_NUMOF) {
-        return -1;
+        return UART_NODEV;
     }
     uart = _uart(dev);
 
@@ -77,7 +77,7 @@ int uart_init(uart_t dev, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     uart->IEN |= USART_IEN_RXDATAV;
     /* enable receiver and transmitter */
     uart->CMD = USART_CMD_TXEN | USART_CMD_RXEN;
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t dev, const uint8_t *data, size_t len)
diff --git a/cpu/kinetis_common/periph/uart.c b/cpu/kinetis_common/periph/uart.c
index 700fdc72db..83c2bb0c2e 100644
--- a/cpu/kinetis_common/periph/uart.c
+++ b/cpu/kinetis_common/periph/uart.c
@@ -59,8 +59,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* do basic initialization */
     int res = init_base(uart, baudrate);
-
-    if (res < 0) {
+    if (res != UART_OK) {
         return res;
     }
 
@@ -88,11 +87,10 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 #endif
 
         default:
-            return -2;
-            break;
+            return UART_NODEV;
     }
 
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -134,7 +132,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
 #endif
 
         default:
-            return -1;
+            return UART_NODEV;
     }
 
     /* configure RX and TX pins, set pin to use alternative function mode */
@@ -179,7 +177,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
 
     /* enable transmitter and receiver */
     dev->C2 |= UART_C2_TE_MASK | UART_C2_RE_MASK;
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/lm4f120/periph/uart.c b/cpu/lm4f120/periph/uart.c
index 67c6e4e13e..bcf3061377 100644
--- a/cpu/lm4f120/periph/uart.c
+++ b/cpu/lm4f120/periph/uart.c
@@ -43,11 +43,11 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     assert(uart == 0);
     /* Check to make sure the UART peripheral is present */
     if(!ROM_SysCtlPeripheralPresent(SYSCTL_PERIPH_UART0)){
-        return -1;
+        return UART_NODEV;
     }
 
     int res = init_base(uart, baudrate);
-    if(res < 0){
+    if(res != UART_OK){
         return res;
     }
 
@@ -76,7 +76,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
             break;
 #endif
     }
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -99,8 +99,10 @@ static int init_base(uart_t uart, uint32_t baudrate)
             ROM_UARTEnable(UART0_BASE);
             break;
 #endif
+        default:
+            return UART_NODEV;
         }
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/lpc11u34/periph/uart.c b/cpu/lpc11u34/periph/uart.c
index 39ef755e95..1859783ae5 100644
--- a/cpu/lpc11u34/periph/uart.c
+++ b/cpu/lpc11u34/periph/uart.c
@@ -35,7 +35,7 @@ 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, void *arg)
 {
     int res = init_base(uart, baudrate);
-    if (res < 0) {
+    if (res != UART_OK) {
         return res;
     }
 
@@ -55,7 +55,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 #endif
     }
 
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -65,7 +65,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
         case UART_0:
             /* this implementation only supports 115200 baud */
             if (baudrate != 115200) {
-                return -2;
+                return UART_NOBAUD;
             }
 
             /* select and configure the pin for RX */
@@ -91,10 +91,10 @@ static int init_base(uart_t uart, uint32_t baudrate)
             break;
 #endif
         default:
-            return -1;
+            return UART_NODEV;
     }
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/lpc1768/periph/uart.c b/cpu/lpc1768/periph/uart.c
index 304717792e..7b8fa676d7 100644
--- a/cpu/lpc1768/periph/uart.c
+++ b/cpu/lpc1768/periph/uart.c
@@ -35,7 +35,7 @@ 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, void *arg)
 {
     int res = init_base(uart, baudrate);
-    if (res < 0) {
+    if (res != UART_OK) {
         return res;
     }
 
@@ -64,7 +64,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 #endif
     }
 
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -74,7 +74,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
         case UART_0:
             /* this implementation only supports 115200 baud */
             if (baudrate != 115200) {
-                return -2;
+                return UART_NOBAUD;
             }
 
             /* power on UART device and select peripheral clock */
@@ -105,7 +105,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
         case UART_1:
             /* this implementation only supports 115200 baud */
             if (baudrate != 115200) {
-                return -2;
+                return UART_NOBAUD;
             }
 
             /* power on UART device and select peripheral clock */
@@ -133,10 +133,10 @@ static int init_base(uart_t uart, uint32_t baudrate)
             break;
 #endif
         default:
-            return -1;
+            return UART_NODEV;
     }
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/lpc2387/periph/uart.c b/cpu/lpc2387/periph/uart.c
index be5926cb38..feb801feca 100644
--- a/cpu/lpc2387/periph/uart.c
+++ b/cpu/lpc2387/periph/uart.c
@@ -39,7 +39,7 @@ int uart_init(uart_t dev, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     (void) baudrate;
     /* for now, we only support one UART device and only the RX interrupt */
     if (dev != 0) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* save interrupt context */
@@ -66,7 +66,7 @@ int uart_init(uart_t dev, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     /* install and enable the IRQ handler */
     install_irq(UART0_INT, UART0_IRQHandler, 6);
     U0IER |= BIT0;       /* enable only RX irq */
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/msp430fxyz/periph/uart.c b/cpu/msp430fxyz/periph/uart.c
index 58e0e3e10e..22a37b1bbe 100644
--- a/cpu/msp430fxyz/periph/uart.c
+++ b/cpu/msp430fxyz/periph/uart.c
@@ -38,8 +38,9 @@ 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, void *arg)
 {
-    if (init_base(uart, baudrate) < 0) {
-        return -1;
+    int res = init_base(uart, baudrate);
+    if (res != UART_OK) {
+        return res;
     }
 
     /* save interrupt context */
@@ -50,13 +51,13 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     UART_IF &= ~(UART_IE_RX_BIT);
     UART_IF |=  (UART_IE_TX_BIT);
     UART_IE |=  (UART_IE_RX_BIT);
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
 {
     if (uart != 0) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* get the default UART for now -> TODO: enable for multiple devices */
@@ -85,7 +86,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
     uart_poweron(uart);
     /* and finally release the software reset bit */
     dev->CTL &= ~(USART_CTL_SWRST);
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/native/periph/uart.c b/cpu/native/periph/uart.c
index 04ce96cefe..926ccb930b 100644
--- a/cpu/native/periph/uart.c
+++ b/cpu/native/periph/uart.c
@@ -98,7 +98,7 @@ static void io_signal_handler(int fd, void *arg)
 int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     if (uart >= UART_NUMOF) {
-        return -1;
+        return UART_NODEV;
     }
 
     struct termios termios;
@@ -133,7 +133,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     case 115200: speed = B115200; break;
     case 230400: speed = B230400 ; break;
     default:
-        return -1;
+        return UART_NOBAUD;
         break;
     }
 
@@ -143,7 +143,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     tty_fds[uart] = real_open(tty_device_filenames[uart], O_RDWR | O_NONBLOCK);
 
     if (tty_fds[uart] < 0) {
-        return -3;
+        return UART_INTERR;
     }
 
     tcsetattr(tty_fds[uart], TCSANOW, &termios);
@@ -154,7 +154,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     native_async_read_setup();
     native_async_read_add_handler(tty_fds[uart], NULL, io_signal_handler);
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/nrf5x_common/periph/uart.c b/cpu/nrf5x_common/periph/uart.c
index 067c7a6f27..fa6b6f5582 100644
--- a/cpu/nrf5x_common/periph/uart.c
+++ b/cpu/nrf5x_common/periph/uart.c
@@ -41,7 +41,7 @@ static uart_isr_ctx_t uart_config;
 int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     if (uart != 0) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* remember callback addresses and argument */
@@ -122,7 +122,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
             NRF_UART0->BAUDRATE = UART_BAUDRATE_BAUDRATE_Baud921600;
             break;
         default:
-            return -2;
+            return UART_NOBAUD;
     }
 
     /* enable the UART device */
@@ -133,7 +133,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     /* enable global and receiving interrupt */
     NVIC_EnableIRQ(UART_IRQN);
     NRF_UART0->INTENSET = UART_INTENSET_RXDRDY_Msk;
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/sam3/periph/uart.c b/cpu/sam3/periph/uart.c
index 6548071bff..6aff70af33 100644
--- a/cpu/sam3/periph/uart.c
+++ b/cpu/sam3/periph/uart.c
@@ -38,7 +38,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 
     /* make sure given device is valid */
     if (uart >= UART_NUMOF) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* get base register */
@@ -71,7 +71,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     NVIC_EnableIRQ(uart_config[uart].irqn);
     dev->UART_IER = UART_IER_RXRDY;
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/samd21/periph/uart.c b/cpu/samd21/periph/uart.c
index 966c9876d4..556f1dc582 100644
--- a/cpu/samd21/periph/uart.c
+++ b/cpu/samd21/periph/uart.c
@@ -50,7 +50,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* initialize basic functionality */
     int res = init_base(uart, baudrate);
-    if (res != 0) {
+    if (res != UART_OK) {
         return res;
     }
 
@@ -60,7 +60,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     /* configure interrupts and enable RX interrupt */
     _uart(uart)->INTENSET.reg = SERCOM_USART_INTENSET_RXC;
     NVIC_EnableIRQ(SERCOM0_IRQn + _sercom_id(_uart(uart)));
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -69,7 +69,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
     SercomUsart *dev;
 
     if ((unsigned int)uart >= UART_NUMOF) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* get the devices base register */
@@ -101,7 +101,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
     while (dev->SYNCBUSY.reg & SERCOM_USART_SYNCBUSY_CTRLB) {}
     /* finally, enable the device */
     dev->CTRLA.reg |= SERCOM_USART_CTRLA_ENABLE;
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/saml21/periph/uart.c b/cpu/saml21/periph/uart.c
index bf0a05e311..34c9f7d88b 100644
--- a/cpu/saml21/periph/uart.c
+++ b/cpu/saml21/periph/uart.c
@@ -39,8 +39,8 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* initialize basic functionality */
     int res = init_base(uart, baudrate);
-    if (res != 0) {
-        return res;
+    if (res != UART_OK) {
+        return UART_NODEV;
     }
 
     /* register callbacks */
@@ -55,7 +55,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
             UART_0_DEV.INTENSET.bit.RXC = 1;
         break;
     }
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -113,11 +113,11 @@ static int init_base(uart_t uart, uint32_t baudrate)
 #endif
         default:
             (void)baud_calculated;
-            return -1;
+            return UART_NODEV;
     }
 
     uart_poweron(uart);
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/stm32f0/periph/uart.c b/cpu/stm32f0/periph/uart.c
index 20365cd6b7..76af555b0b 100644
--- a/cpu/stm32f0/periph/uart.c
+++ b/cpu/stm32f0/periph/uart.c
@@ -45,7 +45,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 
     /* initialize UART in blocking mode first */
     res = init_base(uart, baudrate);
-    if (res < 0) {
+    if (res != UART_OK) {
         return res;
     }
 
@@ -69,7 +69,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     uart_config[uart].rx_cb = rx_cb;
     uart_config[uart].arg = arg;
 
-    return 0;
+    return UART_OK;
 }
 
 int init_base(uart_t uart, uint32_t baudrate)
@@ -110,7 +110,7 @@ int init_base(uart_t uart, uint32_t baudrate)
             break;
 #endif
         default:
-            return -1;
+            return UART_NODEV;
     }
 
     /* Make sure port and dev are != NULL here, i.e. that the variables are
@@ -149,7 +149,7 @@ int init_base(uart_t uart, uint32_t baudrate)
     /* enable receive and transmit mode */
     dev->CR1 |= USART_CR1_UE | USART_CR1_TE | USART_CR1_RE;
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/stm32f1/periph/uart.c b/cpu/stm32f1/periph/uart.c
index 0e3cd765f9..c46a867fff 100644
--- a/cpu/stm32f1/periph/uart.c
+++ b/cpu/stm32f1/periph/uart.c
@@ -58,7 +58,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 
     /* make sure the given device is valid */
     if (uart >= UART_NUMOF) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* save ISR context */
@@ -89,7 +89,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     dev(uart)->CR1 = (USART_CR1_UE | USART_CR1_TE |
                       USART_CR1_RE | USART_CR1_RXNEIE);
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/stm32f2/periph/uart.c b/cpu/stm32f2/periph/uart.c
index 593df0a204..148e86b13c 100644
--- a/cpu/stm32f2/periph/uart.c
+++ b/cpu/stm32f2/periph/uart.c
@@ -75,7 +75,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 
     /* check if given UART device does exist */
     if (uart < 0 || uart >= UART_NUMOF) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* check if baudrate is reachable and choose the right oversampling method*/
@@ -88,7 +88,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
         over8 = 1;
     }
     else {
-        return -2;
+        return UART_NOBAUD;
     }
 
     /* get UART base address */
@@ -147,7 +147,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     NVIC_EnableIRQ(uart_config[uart].irqn);
     dma_isr_enable(uart_config[uart].dma_stream);
     dev->CR1 |= USART_CR1_RXNEIE;
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/stm32f3/periph/uart.c b/cpu/stm32f3/periph/uart.c
index d8f8473d18..e7ea3cadbb 100644
--- a/cpu/stm32f3/periph/uart.c
+++ b/cpu/stm32f3/periph/uart.c
@@ -34,7 +34,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* do basic initialization */
     int res = init_base(uart, baudrate);
-    if (res < 0) {
+    if (res != UART_OK) {
         return res;
     }
 
@@ -64,7 +64,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 #endif
     }
 
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -116,7 +116,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
             break;
 #endif
         default:
-            return -1;
+            return UART_NODEV;
     }
 
     /* Make sure port and dev are != NULL here, i.e. that the variables are
@@ -157,7 +157,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
     dev->CR2 = 0;
     dev->CR1 |= USART_CR1_UE | USART_CR1_TE | USART_CR1_RE;
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/stm32f4/periph/uart.c b/cpu/stm32f4/periph/uart.c
index 4a22faf476..e287ac585b 100644
--- a/cpu/stm32f4/periph/uart.c
+++ b/cpu/stm32f4/periph/uart.c
@@ -55,7 +55,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 
     /* check if given UART device does exist */
     if ((unsigned int)uart >= UART_NUMOF) {
-        return -1;
+        return UART_NODEV;
     }
 
     /* get UART base address */
@@ -104,7 +104,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
     NVIC_EnableIRQ(uart_config[uart].irqn);
     dma_isr_enable(uart_config[uart].dma_stream);
     dev->CR1 |= USART_CR1_RXNEIE;
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)
diff --git a/cpu/stm32l1/periph/uart.c b/cpu/stm32l1/periph/uart.c
index ef037fcee8..81c978305e 100644
--- a/cpu/stm32l1/periph/uart.c
+++ b/cpu/stm32l1/periph/uart.c
@@ -35,7 +35,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     /* do basic initialization */
     int res = init_base(uart, baudrate);
-    if (res < 0) {
+    if (res != UART_OK) {
         return res;
     }
 
@@ -65,7 +65,7 @@ int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 #endif
     }
 
-    return 0;
+    return UART_OK;
 }
 
 static int init_base(uart_t uart, uint32_t baudrate)
@@ -110,7 +110,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
             break;
 #endif
         default:
-            return -1;
+            return UART_NODEV;
     }
 
     /* Make sure dev is != NULL here, i.e. that the variable is assigned in
@@ -134,7 +134,7 @@ static int init_base(uart_t uart, uint32_t baudrate)
     dev->CR2 = 0;
     dev->CR1 |= USART_CR1_UE | USART_CR1_TE | USART_CR1_RE;
 
-    return 0;
+    return UART_OK;
 }
 
 void uart_write(uart_t uart, const uint8_t *data, size_t len)