diff --git a/avr/devices/n00/n00_defs.asm b/avr/devices/n00/n00_defs.asm
index 4c6b549..fac8d5e 100644
--- a/avr/devices/n00/n00_defs.asm
+++ b/avr/devices/n00/n00_defs.asm
@@ -47,7 +47,8 @@
 ; ---------------------------------------------------------------------------
 ; COM module
 
-.equ COM_BIT_LENGTH      = 52000 ; 104000=9600, 52000=19200, 26000=38400
+.equ COM_BIT_LENGTH      = 52000 ; 104000ns=9600, 52000ns=19200, 26000ns=38400
+.equ COM_HALFBIT_LENGTH  = 26000 ; see https://de.wikipedia.org/wiki/Universal_Asynchronous_Receiver_Transmitter
 
 .equ COM_DDR_DATA        = DDRA
 .equ COM_PORT_DATA       = PORTA
diff --git a/avr/devices/n06/n06_defs.asm b/avr/devices/n06/n06_defs.asm
index 4c6b549..9cb3ec3 100644
--- a/avr/devices/n06/n06_defs.asm
+++ b/avr/devices/n06/n06_defs.asm
@@ -47,7 +47,8 @@
 ; ---------------------------------------------------------------------------
 ; COM module
 
-.equ COM_BIT_LENGTH      = 52000 ; 104000=9600, 52000=19200, 26000=38400
+.equ COM_BIT_LENGTH      = 52000 ; 104000ns=9600, 52000ns=19200, 26000ns=38400
+.equ COM_HALFBIT_LENGTH  = 26000 ; see https://de.wikipedia.org/wiki/Universal_Asynchronous_Receiver_Transmitter
 
 .equ COM_DDR_DATA        = DDRA
 .equ COM_PORT_DATA       = PORTA
@@ -60,7 +61,7 @@
 .equ COM_PINNUM_ATTN     = PORTA7
 
 .equ COM_IRQ_ADDR_ATTN   = PCMSK0
-.equ COM_IRQ_BIT_ATTN    = 7              ; bit 7 in PCMSK0
+.equ COM_IRQ_BIT_ATTN    = PCINT7              ; bit 7 in PCMSK0
 .equ COM_IRQ_GIFR_ATTN   = PCIF0
 .equ COM_IRQ_GIMSK_ATTN  = PCIE0
 
diff --git a/avr/devices/n11/n11_defs.asm b/avr/devices/n11/n11_defs.asm
index 52bd6f0..b6b3abf 100644
--- a/avr/devices/n11/n11_defs.asm
+++ b/avr/devices/n11/n11_defs.asm
@@ -47,7 +47,7 @@
 ; COM module
 
 .equ COM_BIT_LENGTH      = 52000 ; 104000ns=9600, 52000ns=19200, 26000ns=38400
-                                 ; see https://de.wikipedia.org/wiki/Universal_Asynchronous_Receiver_Transmitter
+.equ COM_HALFBIT_LENGTH  = 26000 ; see https://de.wikipedia.org/wiki/Universal_Asynchronous_Receiver_Transmitter
 .equ COM_DDR_DATA        = DDRA
 .equ COM_PORT_DATA       = PORTA
 .equ COM_PIN_DATA        = PINA
@@ -59,7 +59,7 @@
 .equ COM_PINNUM_ATTN     = PORTA7
 
 .equ COM_IRQ_ADDR_ATTN   = PCMSK0
-.equ COM_IRQ_BIT_ATTN    = 7              ; bit 7 in PCMSK0
+.equ COM_IRQ_BIT_ATTN    = PCINT7        ; bit 7 in PCMSK0
 .equ COM_IRQ_GIFR_ATTN   = PCIF0
 .equ COM_IRQ_GIMSK_ATTN  = PCIE0
 
diff --git a/avr/devices/n11/n11_main.asm b/avr/devices/n11/n11_main.asm
index ae43814..0054078 100644
--- a/avr/devices/n11/n11_main.asm
+++ b/avr/devices/n11/n11_main.asm
@@ -161,6 +161,10 @@ firmwareStart:   rjmp main
     .include "modules/comproto/msg_device.asm"
     .include "modules/comproto/msg_reboot.asm"
   #endif
+  #ifdef MODULES_LCD
+    .include "modules/com2/screen.asm"
+    .include "modules/comproto/screen.asm"
+  #endif
 #endif
 #ifdef MODULES_TWI_MASTER
   .include "modules/twimaster/main.asm"
@@ -194,9 +198,18 @@ firmwareStart:   rjmp main
 
 .dseg
 
+programRamBegin:
+#ifdef MODULES_LCD
+  screenCounter:               .byte 1
+#endif
+
+programRamEnd:
+
+
 
 #ifdef MODULES_LCD
   sramTimerWriteStats:         .byte 2
+  sramTimerScreen:             .byte 2
 #endif
 sramTimerEnqueueValues:        .byte 2
 #ifdef MODULES_SI7021
@@ -221,12 +234,6 @@ sramTimerEnqueueValues:        .byte 2
 
 .cseg
 
-#ifdef MODULES_LED
-ledA3Flash:    .db DDRA+0x20, PORTA+0x20, PINA+0x20, (1<<PORTA3)
-blinkPattern:  .db 2, 50, 0xff, 0xff   ; 1 short blink, 5s pause, restart
-;blinkPattern2: .db 2, 2, 0xff, 0xff   ; 1 short blink, short pause, restart
-#endif
-
 
 
 ; ---------------------------------------------------------------------------
@@ -242,8 +249,9 @@ timerList:
   .dw statsSendTimer,              Stats_Timer,                TIMER_FLAGS_IF_ADDR, 3000   ; every 5m
 #endif
 #ifdef MODULES_LCD
-;  .dw sramPeriodicalLcdMark,       periodicalLcdMark,          0,                    20    ; every 2s
-  .dw sramTimerWriteStats,         writeStats,                 0,                   100
+;  .dw sramPeriodicalLcdMark,       periodicalLcdMark,          0,                    20   ; every 2s
+;  .dw sramTimerWriteStats,         writeStats,                 0,                   100
+  .dw sramTimerScreen,              printScreen,                TIMER_FLAGS_IF_ADDR,  50    ; every 5s
 #endif
 #ifdef MODULES_SI7021
   .dw sramTimerSI7021Measure,      SI7021_OnTimer,             0,                   300    ; every 30s
@@ -292,18 +300,55 @@ systemSetBootSpeed:
 ; Called on first time run, i.e. on system start. No arguments, no results.
 
 onSystemStart:
+  ldi xh, HIGH(programRamBegin)
+  ldi xl, LOW(programRamBegin)
+  clr r16
+  ldi r17, (programRamEnd-programRamBegin)
+  rcall Utils_FillSram
   ret
 
 
 #ifdef MODULES_LCD
-periodicalLcdMark:
-  rcall printTimerMark
+
+printScreen:
+  lds r16, screenCounter
+  tst r16
+  brne printScreen_l1
+  rcall CPRO_Screen
+  rjmp printScreen_counter
+printScreen_l1:
+  cpi r16, 1
+  brne printScreen_l2
+  rcall COM2_Screen_RecvStats
+  rjmp printScreen_counter
+printScreen_l2:
+;  cpi r16, 2
+;  brne printScreen_l3
+;  rcall COM2_Screen_SendStats
+;  rjmp printScreen_counter
+printScreen_l3:
+  ; add more screens here
+
+printScreen_counter:
+  lds r16, screenCounter
+  inc r16
+  cpi r16, 2 ; number of screens
+  brcs printScreen_store
+  clr r16
+printScreen_store:
+  sts screenCounter, r16
+printScreen_end:
   ret
 
 
-writeStats:
-  rcall printSendStats
-  ret
+;periodicalLcdMark:
+;  rcall printTimerMark
+;  ret
+
+
+;writeStats:
+;  rcall printSendStats
+;  ret
 #endif
 
 
diff --git a/avr/devices/n12/n12_defs.asm b/avr/devices/n12/n12_defs.asm
index 1fb450d..f205415 100644
--- a/avr/devices/n12/n12_defs.asm
+++ b/avr/devices/n12/n12_defs.asm
@@ -45,7 +45,8 @@
 ; ---------------------------------------------------------------------------
 ; COM module
 
-.equ COM_BIT_LENGTH      = 52000 ; 104000=9600, 52000=19200, 26000=38400
+.equ COM_BIT_LENGTH      = 52000 ; 104000ns=9600, 52000ns=19200, 26000ns=38400
+.equ COM_HALFBIT_LENGTH  = 26000 ; see https://de.wikipedia.org/wiki/Universal_Asynchronous_Receiver_Transmitter
 
 .equ COM_DDR_DATA        = DDRA
 .equ COM_PORT_DATA       = PORTA
diff --git a/avr/devices/n14/n14_defs.asm b/avr/devices/n14/n14_defs.asm
index b3bea1e..e043058 100644
--- a/avr/devices/n14/n14_defs.asm
+++ b/avr/devices/n14/n14_defs.asm
@@ -42,7 +42,8 @@
 ; ---------------------------------------------------------------------------
 ; COM module
 
-.equ COM_BIT_LENGTH      = 52000 ; 104000=9600, 52000=19200, 26000=38400
+.equ COM_BIT_LENGTH      = 52000 ; 104000ns=9600, 52000ns=19200, 26000ns=38400
+.equ COM_HALFBIT_LENGTH  = 26000 ; see https://de.wikipedia.org/wiki/Universal_Asynchronous_Receiver_Transmitter
 
 .equ COM_DDR_DATA        = DDRB
 .equ COM_PORT_DATA       = PORTB
diff --git a/avr/modules/com2/lowlevel.asm b/avr/modules/com2/lowlevel.asm
index cfe44e2..5ff7a97 100644
--- a/avr/modules/com2/lowlevel.asm
+++ b/avr/modules/com2/lowlevel.asm
@@ -31,7 +31,7 @@ com2SendByte:
   ; send startbit
   cbi COM_PORT_DATA, COM_PINNUM_DATA              ; +2 set DATA low
   sbi COM_DDR_DATA, COM_PINNUM_DATA               ; +2 set DATA as output
-  Utils_WaitNanoSecs COM_BIT_LENGTH, 5, r22       ; wait for one bit duration
+  Utils_WaitNanoSecs COM_BIT_LENGTH, 1, r22       ; wait for one bit duration
   ; send data bits
 com2SendByte_loop:                                ; 9 for low bit
     lsr r16                                       ; 1+ bit to send -> CARRY
@@ -43,16 +43,16 @@ com2SendByte_setLow:
 com2SendByte_setHigh:
     cbi COM_DDR_DATA, COM_PINNUM_DATA             ; +2 set DATA as input, pullup R makes it ONE
     nop                                           ; +1 (to make pin change available)
-    Utils_WaitNanoSecs COM_BIT_LENGTH/2, 11, r22  ; wait for half a bit length for line to safely settle
+    Utils_WaitNanoSecs COM_HALFBIT_LENGTH, 0, r22  ; wait for half a bit length for line to safely settle
     sbis COM_PIN_DATA, COM_PINNUM_DATA            ; +1 if no skip, +2 if skipped
       rjmp com2SendByte_error                     ; +2 if error (collision: we wanted line to be high but it is low)
-    Utils_WaitNanoSecs COM_BIT_LENGTH/2, 0, r22
+    Utils_WaitNanoSecs COM_HALFBIT_LENGTH, 11, r22
 com2SendByte_loopEnd:
     dec r21                                       ; +1
   brne com2SendByte_loop                          ; +2, sum per loop: 10 cycles
   ; send stopbit
   cbi COM_DDR_DATA, COM_PINNUM_DATA               ; +2 set DATA as input, pullup R makes it ONE
-  Utils_WaitNanoSecs COM_BIT_LENGTH, 4, r22       ; wait for one bit length
+  Utils_WaitNanoSecs COM_BIT_LENGTH, 0, r22       ; wait for one bit length
   rjmp com2LowLevelSecRet
 
 com2SendByte_error:
@@ -81,7 +81,7 @@ com2ReceiveByte:
   ; wait for startbit
   rcall com2WaitForDataLow                     ; (R16, R17, R22)
   brcc com2ReceiveByte_error
-  Utils_WaitNanoSecs COM_BIT_LENGTH/2, 5, r22  ; goto middle of startbit to maximize sync stability
+  Utils_WaitNanoSecs COM_HALFBIT_LENGTH, 10, r22  ; goto middle of startbit to maximize sync stability
 com2ReceiveByte_loop:
     Utils_WaitNanoSecs COM_BIT_LENGTH, 8, r22  ; 8 cycles used in the complete loop between waits
     sec                                        ; +1
@@ -149,7 +149,7 @@ com2WaitForAttnHigh:
 ; ---------------------------------------------------------------------------
 ; com2WaitForDataState1ms
 ;
-; Waits up to 1ms for high DATA line
+; Waits up to 500us for high DATA line
 ; IN:
 ; - R16: state to wait for (00 for low, 0xff for high)
 ; OUT:
@@ -163,12 +163,14 @@ com2WaitForDataState1ms_loop:
     eor r22, r16
     andi r22, (1<<COM_PINNUM_DATA)
     breq com2WaitForDataState1ms_stateReached
-    rcall Utils_WaitFor10MicroSecs                ; wait for 10us (R22)
+;    rcall Utils_WaitFor10MicroSecs                ; wait for 10us (R22)
+    Utils_WaitNanoSecs 5000, 0, r22
     dec r17
   brne com2WaitForDataState1ms_loop
   rjmp com2LowLevelClcRet
 com2WaitForDataState1ms_stateReached:
-  rjmp com2LowLevelSecRet
+  sec
+  ret
 
 
 
diff --git a/avr/modules/com2/main.asm b/avr/modules/com2/main.asm
index 001176b..f722a45 100644
--- a/avr/modules/com2/main.asm
+++ b/avr/modules/com2/main.asm
@@ -26,6 +26,7 @@ com2RecvStatsBegin:        ; 12 bytes
   com2StatsIoError:        .byte 2
   com2StatsNoBufferError:  .byte 2
   com2StatsHandled:        .byte 2
+  com2StatsNotForMe:       .byte 2
   com2StatsMissed:         .byte 2   ; currently not used
 com2RecvStatsEnd:
 
@@ -331,6 +332,8 @@ com2ReceivePacket_error:
   breq com2ReceivePacket_ioError
   cpi r16, COM2_ERROR_DATAERROR
   breq com2ReceivePacket_dataError
+  cpi r16, COM2_ERROR_NOTFORME
+  breq com2ReceivePacket_notForMe
   rjmp com2ReceivePacket_retnc
 com2ReceivePacket_ioError:
   ldi xl, LOW(com2StatsIoError)
@@ -340,6 +343,10 @@ com2ReceivePacket_dataError:
   ldi xl, LOW(com2StatsContentError)
   ldi xh, HIGH(com2StatsContentError)
   rjmp com2ReceivePacket_incCounterDeallocNc
+com2ReceivePacket_notForMe:
+  ldi xl, LOW(com2StatsNotForMe)
+  ldi xh, HIGH(com2StatsNotForMe)
+  rjmp com2ReceivePacket_incCounterDeallocNc
 com2ReceivePacket_incCounterDeallocNc:
   rcall Utils_IncrementCounter16         ; (r18, r19, 22)
 com2ReceivePacket_deallocRetnc:
diff --git a/avr/modules/com2/packets.asm b/avr/modules/com2/packets.asm
index 46df318..39b7ebc 100644
--- a/avr/modules/com2/packets.asm
+++ b/avr/modules/com2/packets.asm
@@ -77,7 +77,6 @@ COM2_SendPacketWithAttn:
   push r15
     in r15, SREG
     cli
-;    rcall com2WaitForOneBitLength                  ; wait for one bit duration (R22)
     ; check for ATTN line: busy?
     cbi COM_PORT_ATTN, COM_PINNUM_ATTN             ; disable pullup on ATTN
     cbi COM_DDR_ATTN, COM_PINNUM_ATTN              ; set ATTN as input
@@ -87,7 +86,8 @@ COM2_SendPacketWithAttn:
   
     cbi COM_PORT_ATTN, COM_PINNUM_ATTN             ; set ATTN low
     sbi COM_DDR_ATTN, COM_PINNUM_ATTN              ; set ATTN as output
-    rcall com2WaitForOneBitLength                    ; wait for one bit duration (R22)
+    rcall com2WaitForOneBitLength                  ; wait for one bit duration (R22)
+    rcall com2WaitForOneBitLength                  ; wait for another bit duration (R22)
 
     adiw xh:xl, COM2_MSG_OFFS_MSGLEN
     ld r16, X