diff --git a/cpu/avr/dev/rs232.c b/cpu/avr/dev/rs232.c
index ecf5a442d..44621f777 100644
--- a/cpu/avr/dev/rs232.c
+++ b/cpu/avr/dev/rs232.c
@@ -28,7 +28,6 @@
  *
  * This file is part of the Contiki operating system.
  *
- * @(#)$Id: rs232.c,v 1.7 2010/10/27 14:51:20 dak664 Exp $
  */
 
 #include <stdio.h>
@@ -50,229 +49,339 @@
 #define USART_UCSRC_SEL 0x00
 #endif
 
+/* Currently only the STK500 platform uses a static RAM buffer for printfs.
+ * Others print a character at a time using the gcc string pointer.
+ * gcc may not strip the unused buffer, even though it is statically
+ * allocated in an unused routine.
+ */
 #ifdef RS232_CONF_PRINTF_BUFFER_LENGTH
 #define RS232_PRINTF_BUFFER_LENGTH RS232_CONF_PRINTF_BUFFER_LENGTH
 #else
+#if CONTIKI_TARGET_STK500
 #define RS232_PRINTF_BUFFER_LENGTH 64
 #endif
-
-#ifndef ADD_CARRAGE_RETURNS_TO_SERIAL_OUTPUT
-#define ADD_CARRAGE_RETURNS_TO_SERIAL_OUTPUT 1
 #endif
 
-typedef struct {
-  volatile uint8_t * udr;
-  volatile uint8_t * ubrrh;
-  volatile uint8_t * ubrrl;
-  volatile uint8_t * ucsrb;
-  volatile uint8_t * ucsrc;
-  volatile uint8_t txwait;
-  int (* input_handler)(unsigned char);
-} rs232_t;
+/* TX interrupts would allow non-blocking output up to the size of some RAM buffer.
+ * Since a RAM buffer is not implemented tx interrupts are superfluous and unwanted
+ * because they block debug prints from within interrupt routines
+ */
+#ifdef RS232_CONF_TX_INTERRUPTS
+#define RS232_TX_INTERRUPTS RS232_CONF_TX_INTERRUPTS
+#else
+#define RS232_TX_INTERRUPTS 0
+#endif
+
+/* Insert a carriage return after a line feed. This is the default. */
+#ifndef ADD_CARRIAGE_RETURN_AFTER_NEWLINE
+#define ADD_CARRIAGE_RETURN_AFTER_NEWLINE 1
+#endif
+
+/* Reducing NUMPORTS from the default will harmlessly disable usage of those ports */
+/* Two ports take 400 bytes flash and 4 bytes RAM. */
+#ifdef RS232_CONF_NUMPORTS
+#define NUMPORTS RS232_CONF_NUMPORTS
+#endif
 
 #if defined (__AVR_ATmega128__) || defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega1281__) || defined(__AVR_ATmega128RFA1__)
-static rs232_t rs232_ports[2] = {
-  {   // UART0
-    &UDR0,
-    &UBRR0H,
-    &UBRR0L,
-    &UCSR0B,
-    &UCSR0C,
-    0,
-    NULL
-  },
+#ifndef NUMPORTS
+#define NUMPORTS 2
+#elif NUMPORTS > 2
+#error Only two serial ports are defined for this processor!
+#endif
+
+#if NUMPORTS > 0
+#define D_UDR0   UDR0
+#define D_UDRE0M (1 << UDRE0)
+#define D_UBRR0H UBRR0H
+#define D_UBRR0L UBRR0L
+#define D_UCSR0A UCSR0A
+#define D_UCSR0B UCSR0B
+#define D_UCSR0C UCSR0C
+#define D_USART0_RX_vect USART0_RX_vect
+#define D_USART0_TX_vect USART0_TX_vect
+
+#if NUMPORTS > 1
+#define D_UDR1   UDR1
+#define D_UDRE1M (1 << UDRE1)
+#define D_UBRR1H UBRR1H
+#define D_UBRR1L UBRR1L
+#define D_UCSR1A UCSR1A
+#define D_UCSR1B UCSR1B
+#define D_UCSR1C UCSR1C
+#define D_USART1_RX_vect USART1_RX_vect
+#define D_USART1_TX_vect USART1_TX_vect
+#endif
+
+#endif
 
-  {  // UART1
-    &UDR1,
-    &UBRR1H,
-    &UBRR1L,
-    &UCSR1B,
-    &UCSR1C,
-    0,
-    NULL
-  }
-};
 #elif defined (__AVR_AT90USB1287__)
 /* Has only UART1, map it to port 0 */
-static rs232_t rs232_ports[1] = {
-  {  // UART1
-    &UDR1,
-    &UBRR1H,
-    &UBRR1L,
-    &UCSR1B,
-    &UCSR1C,
-    0,
-    NULL
-  }
-};
-#elif defined (__AVR_ATmega8__) || defined (__AVR_ATmega8515__) \
-  || defined (__AVR_ATmega16__) || defined (__AVR_ATmega32__)
-static rs232_t rs232_ports[1] = {
-  {   // UART0
-    &UDR,
-    &UBRRH,
-    &UBRRL,
-    &UCSRB,
-    &UCSRC,
-    0,
-    NULL
-  }
-};
-#elif defined (__AVR_ATmega644__) || defined (__AVR_ATmega328P__)
-static rs232_t rs232_ports[1] = {
-  {   // UART0
-    &UDR0,
-    &UBRR0H,
-    &UBRR0L,
-    &UCSR0B,
-    &UCSR0C,
-    0,
-    NULL
-  }
-};
+#ifndef NUMPORTS
+#define NUMPORTS 1
+#elif NUMPORTS > 1
+#error Only one serial port is defined for this processor!
+#endif
+
+#if NUMPORTS > 0
+#define D_UDR0   UDR1
+#define D_UDRE0M (1 << UDRE1)
+#define D_UBRR0H UBRR1H
+#define D_UBRR0L UBRR1L
+#define D_UCSR0A UCSR1A
+#define D_UCSR0B UCSR1B
+#define D_UCSR0C UCSR1C
+#define D_USART0_RX_vect USART1_RX_vect
+#define D_USART0_TX_vect USART1_TX_vect
+#endif
+
+#elif defined (__AVR_ATmega8515__)
+#ifndef NUMPORTS
+#define NUMPORTS 1
+#elif NUMPORTS > 1
+#error Only one serial port is defined for this processor!
+#endif
+
+#if NUMPORTS > 0
+#define D_UDR0   UDR
+#define D_UDRE0M (1 << UDRE)
+#define D_UBRR0H UBRRH
+#define D_UBRR0L UBRRL
+#define D_UCSR0A UCSRA
+#define D_UCSR0B UCSRB
+#define D_UCSR0C UCSRC
+#define D_USART0_RX_vect USART_RX_vect
+#define D_USART0_TX_vect USART_TX_vect
+#endif
+
+#elif defined (__AVR_ATmega328P__)
+#ifndef NUMPORTS
+#define NUMPORTS 1
+#elif NUMPORTS > 1
+#error Only one serial port is defined for this processor!
+#endif
+
+#if NUMPORTS > 0
+#define D_UDR0   UDR0
+#define D_UDRE0M (1 << UDRE0)
+#define D_UBRR0H UBRR0H
+#define D_UBRR0L UBRR0L
+#define D_UCSR0A UCSR0A
+#define D_UCSR0B UCSR0B
+#define D_UCSR0C UCSR0C
+#define D_USART0_RX_vect USART_RX_vect
+#define D_USART0_TX_vect USART_TX_vect
+#endif
+
+#elif defined (__AVR_ATmega8__) || defined (__AVR_ATmega16__) || defined (__AVR_ATmega32__)
+#ifndef NUMPORTS
+#define NUMPORTS 1
+#elif NUMPORTS > 1
+#error Only one serial port is defined for this processor!
+#endif
+
+#if NUMPORTS > 0
+#define D_UDR0   UDR
+#define D_UDRE0M (1 << UDRE)
+#define D_UBRR0H UBRRH
+#define D_UBRR0L UBRRL
+#define D_UCSR0A UCSRA
+#define D_UCSR0B UCSRB
+#define D_UCSR0C UCSRC
+#define D_USART0_RX_vect USART_RXC_vect
+#define D_USART0_TX_vect USART_TXC_vect
+#endif
+
+#elif defined (__AVR_ATmega644__)
+#ifndef NUMPORTS
+#define NUMPORTS 1
+#elif NUMPORTS > 1
+#error Only one serial port is defined for this processor!
+#endif
+
+#if NUMPORTS > 0
+#define D_UDR0   UDR0
+#define D_UDRE0M (1 << UDRE0)
+#define D_UBRR0H UBRR0H
+#define D_UBRR0L UBRR0L
+#define D_UCSR0A UCSR0A
+#define D_UCSR0B UCSR0B
+#define D_UCSR0C UCSR0C
+#define D_USART0_RX_vect USART0_RX_vect
+#define D_USART0_TX_vect USART0_TX_vect
+#endif
+
 #else
 #error Please define the UART registers for your MCU!
 #endif
 
-#if defined (__AVR_ATmega128__) || defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega1281__) || defined(__AVR_ATmega128RFA1__)
-/*---------------------------------------------------------------------------*/
-ISR(USART0_TX_vect)
-{
-  rs232_ports[RS232_PORT_0].txwait = 0;
-}
-
-/*---------------------------------------------------------------------------*/
-ISR(USART0_RX_vect)
+#if NUMPORTS > 0
+int (* input_handler_0)(unsigned char);
+ISR(D_USART0_RX_vect)
 {
   unsigned char c;
-
-  c = *(rs232_ports[RS232_PORT_0].udr);
-
-  if(rs232_ports[RS232_PORT_0].input_handler != NULL) {
-    rs232_ports[RS232_PORT_0].input_handler(c);
-  }
+  c = D_UDR0;
+  if (input_handler_0 != NULL) input_handler_0(c);
 }
-/*---------------------------------------------------------------------------*/
-ISR(USART1_TX_vect)
+#if RS232_TX_INTERRUPTS
+volatile uint8_t txwait_0;
+ISR(D_USART0_TX_vect)
 {
-  rs232_ports[RS232_PORT_1].txwait = 0;
+  txwait_0 = 0;
 }
-
-/*---------------------------------------------------------------------------*/
-ISR(USART1_RX_vect)
-{
-  unsigned char c;
-
-  c = *(rs232_ports[RS232_PORT_1].udr);
-
-  if(rs232_ports[RS232_PORT_1].input_handler != NULL) {
-    rs232_ports[RS232_PORT_1].input_handler(c);
-  }
-}
-
-#elif defined (__AVR_ATmega644__)
-/*---------------------------------------------------------------------------*/
-ISR(USART0_TX_vect)
-{
-  rs232_ports[RS232_PORT_0].txwait = 0;
-}
- /*---------------------------------------------------------------------------*/
-ISR(USART0_RX_vect)
-{
-  unsigned char c;
-
-  c = *(rs232_ports[RS232_PORT_0].udr);
-
-  if(rs232_ports[RS232_PORT_0].input_handler != NULL) {
-    rs232_ports[RS232_PORT_0].input_handler(c);
-   }
-}
-#elif defined (__AVR_ATmega8__) || defined (__AVR_ATmega16__) || defined (__AVR_ATmega32__)
-/*---------------------------------------------------------------------------*/
-ISR(USART_TXC_vect)
-{
-  rs232_ports[RS232_PORT_0].txwait = 0;
-}
-
-/*---------------------------------------------------------------------------*/
-ISR(USART_RXC_vect)
-{
-  unsigned char c;
-
-  c = *(rs232_ports[RS232_PORT_0].udr);
-
-  if(rs232_ports[RS232_PORT_0].input_handler != NULL) {
-    rs232_ports[RS232_PORT_0].input_handler(c);
-  }
-}
-
-#elif defined (__AVR_ATmega8515__) || defined (__AVR_ATmega328P__)
-/*---------------------------------------------------------------------------*/
-ISR(USART_TX_vect)
-{
-  rs232_ports[RS232_PORT_0].txwait = 0;
-}
-
-/*---------------------------------------------------------------------------*/
-ISR(USART_RX_vect)
-{
-  unsigned char c;
-
-  c = *(rs232_ports[RS232_PORT_0].udr);
-
-  if(rs232_ports[RS232_PORT_0].input_handler != NULL) {
-    rs232_ports[RS232_PORT_0].input_handler(c);
-  }
-}
-
-#elif defined (__AVR_AT90USB1287__)
-/*---------------------------------------------------------------------*/
-ISR(USART1_TX_vect)
-{
-  rs232_ports[RS232_PORT_0].txwait = 0;
-}
-
-/*---------------------------------------------------------------------------*/
-ISR(USART1_RX_vect)
-{
-  unsigned char c;
-
-  c = *(rs232_ports[RS232_PORT_0].udr);
-
-  if(rs232_ports[RS232_PORT_0].input_handler != NULL) {
-    rs232_ports[RS232_PORT_0].input_handler(c);
-  }
-}
-#else
-#error Please define the interrupt vectors for your MCU!
 #endif
 
+#if NUMPORTS > 1
+int (* input_handler_1)(unsigned char);
+ISR(D_USART1_RX_vect)
+{
+  unsigned char c;
+  c = D_UDR1;
+  if (input_handler_1 != NULL) input_handler_1(c);
+}
+#if RS232_TX_INTERRUPTS
+volatile uint8_t txwait_1;
+ISR(USART1_TX_vect)
+{
+  txwait_1 = 0;
+}
+#endif
+
+#if NUMPORTS > 2
+int (* input_handler_2)(unsigned char);
+ISR(D_USART2_RX_vect)
+{
+  unsigned char c;
+  c = D_UDR2;
+  if (input_handler_2 != NULL) input_handler_2(c);
+}
+#if RS232_TX_INTERRUPTS
+volatile uint8_t txwait_2;
+ISR(USART2_TX_vect)
+{
+  txwait_2= 0;
+}
+#endif
+#endif
+
+#endif
+#endif
 /*---------------------------------------------------------------------------*/
 void
 rs232_init (uint8_t port, uint8_t bd, uint8_t ffmt)
 {
-  *(rs232_ports[port].ubrrh) = (uint8_t)(bd>>8);
-  *(rs232_ports[port].ubrrl) = (uint8_t)bd;
+#if NUMPORTS > 0
+ if (port == 0) {
+   D_UBRR0H = (uint8_t)(bd>>8);
+   D_UBRR0L = (uint8_t)bd;
+#if RS232_TX_INTERRUPTS
+   txwait_0 = 0;
+   D_UCSR0B =  USART_INTERRUPT_RX_COMPLETE | USART_INTERRUPT_TX_COMPLETE | \
+               USART_RECEIVER_ENABLE | USART_TRANSMITTER_ENABLE;
+#else
+   D_UCSR0B =  USART_INTERRUPT_RX_COMPLETE | \
+               USART_RECEIVER_ENABLE | USART_TRANSMITTER_ENABLE;
+#endif
+   D_UCSR0C = USART_UCSRC_SEL | ffmt;
+   input_handler_0 = NULL;
 
-  /*
-   * - Enable receiver and transmitter,
-   * - Enable interrupts for receiver and transmitter
-   */
-  *(rs232_ports[port].ucsrb) = USART_INTERRUPT_RX_COMPLETE | USART_INTERRUPT_TX_COMPLETE | \
-    USART_RECEIVER_ENABLE | USART_TRANSMITTER_ENABLE;
+#if NUMPORTS > 1
+ } else if (port == 1) {
+   D_UBRR1H = (uint8_t)(bd>>8);
+   D_UBRR1L = (uint8_t)bd;
+#if RS232_TX_INTERRUPTS
+   txwait_1 = 0;
+   D_UCSR1B =  USART_INTERRUPT_RX_COMPLETE | USART_INTERRUPT_TX_COMPLETE | \
+               USART_RECEIVER_ENABLE | USART_TRANSMITTER_ENABLE;
+#else
+   D_UCSR1B =  USART_INTERRUPT_RX_COMPLETE | \
+               USART_RECEIVER_ENABLE | USART_TRANSMITTER_ENABLE;
+#endif
+   D_UCSR1C = USART_UCSRC_SEL | ffmt;
+   input_handler_1 = NULL;
 
-  /*
-   * - mode (sync. / async)
-   * - Parity
-   * - Stop bits
-   * - charater size (9 bits are currently not supported)
-   * - clock polarity
-   */
-  *(rs232_ports[port].ucsrc) = USART_UCSRC_SEL | ffmt;
+#if NUMPORTS > 2
+ } else if (port == 2) {
+   D_UBRR2H = (uint8_t)(bd>>8);
+   D_UBRR2L = (uint8_t)bd;
+#if RS232_TX_INTERRUPTS
+   txwait_2 = 0;
+   D_UCSR2B =  USART_INTERRUPT_RX_COMPLETE | USART_INTERRUPT_TX_COMPLETE | \
+               USART_RECEIVER_ENABLE | USART_TRANSMITTER_ENABLE;
+#else
+   D_UCSR2B =  USART_INTERRUPT_RX_COMPLETE | \
+               USART_RECEIVER_ENABLE | USART_TRANSMITTER_ENABLE;
+#endif
+   D_UCSR2C = USART_UCSRC_SEL | ffmt;
+   input_handler_2 = NULL;
+#endif
+#endif
+ }
+#endif /* NUMPORTS > 0 */
+}
 
-  rs232_ports[port].txwait = 0;
-
-  rs232_ports[port].input_handler = NULL;
+/*---------------------------------------------------------------------------*/
+void 
+rs232_send(uint8_t port, unsigned char c)
+{
+#if RS232_TX_INTERRUPTS
+  /* Output character and block until it is transmitted */
+#if NUMPORTS > 0
+  if (port == 0 ) {
+    txwait_0 = 1;
+    D_UDR0 = c;
+    while (txwait_0);
+#if NUMPORTS > 1
+  } else if (port == 1) {
+    txwait_1 = 1;
+    D_UDR1 = c;
+    while (txwait_1);
+#if NUMPORTS > 2
+  } else if (port == 2) {
+    txwait_2 = 1;
+    D_UDR2 = c;
+    while (txwait_2);
+#endif
+#endif
+  }
+#endif
+#else /* RS232_TX_INTERRUPTS */
+  /* Block until tx ready and output character */
+#if NUMPORTS > 0
+  if (port == 0 ) {
+    while (!(D_UCSR0A & D_UDRE0M));
+    D_UDR0 = c;
+#if NUMPORTS > 1
+  } else if (port == 1) {
+    while (!(D_UCSR1A & D_UDRE1M));
+    D_UDR1 = c;
+#if NUMPORTS > 2
+  } else if (port == 2) {
+    while (!(D_UCSR2A & D_UDRE2M));
+    D_UDR2 = c;
+#endif
+#endif
+  }
+#endif
+#endif /* RS232_TX_INTERRUPTS */
+}
+/*---------------------------------------------------------------------------*/
+void
+rs232_set_input(uint8_t port, int (*f)(unsigned char))
+{
+#if NUMPORTS > 0
+  if (port == 0) {
+    input_handler_0 = f;
+#if NUMPORTS > 1
+  } else if (port == 1) {
+    input_handler_1 = f;
+#if NUMPORTS > 2
+  } else if (port == 2) {
+    input_handler_2 = f;
+#endif
+#endif
+  }
+#endif
 }
 
 void
@@ -288,7 +397,7 @@ void
 rs232_print(uint8_t port, char *buf)
 {
   while(*buf) {
-#if ADD_CARRAGE_RETURNS_TO_SERIAL_OUTPUT
+#if ADD_CARRIAGE_RETURN_AFTER_NEWLINE
     if(*buf=='\n') rs232_send(port, '\r');
 	if(*buf=='\r') buf++; else rs232_send(port, *buf++);
 #else
@@ -296,6 +405,8 @@ rs232_print(uint8_t port, char *buf)
 #endif
   }
 }
+
+#if RS232_PRINTF_BUFFER_LENGTH
 /*---------------------------------------------------------------------------*/
 void
 rs232_printf(uint8_t port, const char *fmt, ...)
@@ -309,20 +420,7 @@ rs232_printf(uint8_t port, const char *fmt, ...)
 
   rs232_print (port, buf);
 }
-/*---------------------------------------------------------------------------*/
-void
-rs232_send(uint8_t port, unsigned char c)
-{
-  rs232_ports[port].txwait = 1;
-  *(rs232_ports[port].udr) = c;
-  while(rs232_ports[port].txwait);
-}
-/*---------------------------------------------------------------------------*/
-void
-rs232_set_input(uint8_t port, int (*f)(unsigned char))
-{
-  rs232_ports[port].input_handler = f;
-}
+#endif
 /*---------------------------------------------------------------------------*/
 void
 slip_arch_writeb(unsigned char c)
@@ -338,7 +436,7 @@ static FILE rs232_stdout = FDEV_SETUP_STREAM(rs232_stdout_putchar,
 
 int rs232_stdout_putchar(char c, FILE *stream)
 {
-#if ADD_CARRAGE_RETURNS_TO_SERIAL_OUTPUT
+#if ADD_CARRIAGE_RETURN_AFTER_NEWLINE
   if(c=='\n') rs232_send(stdout_rs232_port, '\r');
   if(c!='\r') rs232_send (stdout_rs232_port, c);
 #else