diff --git a/avr/devices/all/includes.asm b/avr/devices/all/includes.asm
index 41039f9..83a040b 100644
--- a/avr/devices/all/includes.asm
+++ b/avr/devices/all/includes.asm
@@ -104,6 +104,14 @@
 
 
 
+#ifdef MODULES_COM2W0
+.include "modules/com2w/defs.asm"
+.include "modules/com2w/common.asm"
+.include "modules/com2w/com2w0.asm"
+#endif
+
+
+
 #ifdef MODULES_COM2W1
 .include "modules/com2w/defs.asm"
 .include "modules/com2w/common.asm"
diff --git a/avr/modules/com2w/com2w.asm b/avr/modules/com2w/com2w.asm
index 00c38b4..d888f15 100644
--- a/avr/modules/com2w/com2w.asm
+++ b/avr/modules/com2w/com2w.asm
@@ -98,10 +98,6 @@ COM2W_Every100ms:
 ; @clobbers R16, R17, R18, R19, R20, R22, R24, R25, X
 
 com2wReceiveNextPkg:
-;  ldi r20, 3                          ; make sure clock remains low for at least 15us
-;  rcall com2wWaitForClockHighMulti5Us ; (R20, R22)
-;  brcs com2wReceiveNextPkg_end        ; clock got high quite soon, maybe just flaky line
-
   rcall NET_Buffer_Alloc                          ; R16=buffer num (R16, R17, X)
   brcs com2wReceiveNextPkg_gotBuffer
   ldi r16, NET_IFACE_OFFS_ERR_NOBUF_LOW
@@ -119,13 +115,6 @@ com2wReceiveNextPkg_gotBuffer:
   rcall NET_AddIncomingMsgNum                     ; (R17, R18, X)
   brcs com2wReceiveNextPkg_end
 
-; debug
-push r18
-  push r19
-    rcall LedSimple_SetFastTiming
-  pop r19
-pop r18
-
   push r16
     ldi r16, NET_IFACE_OFFS_ERR_MISSED_LOW
     rcall NET_Interface_IncCounter16              ; (R24, R25)
diff --git a/avr/modules/com2w/com2w0.asm b/avr/modules/com2w/com2w0.asm
new file mode 100644
index 0000000..8d0589e
--- /dev/null
+++ b/avr/modules/com2w/com2w0.asm
@@ -0,0 +1,643 @@
+; ***************************************************************************
+; copyright   : (C) 2025 by Martin Preuss
+; email       : martin@libchipcard.de
+;
+; ***************************************************************************
+; * This file is part of the project "AqHome".                              *
+; * Please see toplevel file COPYING of that project for license details.   *
+; ***************************************************************************
+
+#ifndef AVR_MODULES_COM2W_COM2W0_H
+#define AVR_MODULES_COM2W_COM2W0_H
+
+
+.dseg
+
+com2w0_iface: .byte COM2W_IFACE_SIZE
+
+
+
+.cseg
+
+
+
+
+; ---------------------------------------------------------------------------
+; @routine COM2W0_Init
+;
+; @clobbers 
+
+COM2W0_Init:
+  ldi yl, LOW(com2w0_iface)
+  ldi yh, HIGH(com2w0_iface)
+  rcall NET_Interface_Init                 ; (R16, R17, X)
+  ldi r16, COM2W_MODE_IDLE
+  rcall com2wSetMode                       ; (R17)
+
+  ; setup CLK line (as input, disable internal pull-up resistor)
+  cbi COM_CLK0_DDR, COM_CLK0_PIN           ; set CLK as input
+.ifdef COM_CLK0_PUE
+  inr r16, COM_CLK0_PUE
+  cbr r16, (1<<COM_CLK0_PIN)               ; disable pullup on CLK
+  outr COM_CLK0_PUE, r16
+.else
+  cbi COM_CLK0_OUTPUT, COM_CLK0_PIN        ; disable pullup on CLK
+.endif
+
+  ; setup DATA line (as input, disable internal pull-up resistor)
+  cbi COM_DATA0_DDR, COM_DATA0_PIN         ; set DATA as input
+.ifdef COM_DATA0_PUE
+  inr r16, COM_DATA0_PUE
+  cbr r16, (1<<COM_DATA0_PIN)              ; disable pullup on DATA
+  outr COM_DATA0_PUE, r16
+.else
+  cbi COM_DATA0_OUTPUT, COM_DATA0_PIN      ; disable pullup on DATA
+.endif
+
+  ; setup pin-change interrupt for CLK
+  rcall com2w0EnableClkIrq
+
+  inr r16, COM_IRQ_ADDR_CLK0
+  sbr r16, (1<<COM_IRQ_BIT_CLK0)           ; enable pin change irq for ATTN line
+  outr COM_IRQ_ADDR_CLK0, r16
+
+  inr r16, GIMSK                           ; enable pin change irq PCIE0 or PCIE1
+  sbr r16, (1<<COM_IRQ_GIMSK_CLK0)
+  outr GIMSK, r16
+  ldi r16, (1<<COM_IRQ_GIFR_CLK0)          ; clear pending irq by writing 1 to ATTN bit
+  outr GIFR, r16
+
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine COM2W0_Periodically @global
+;
+; @clobbers R16, Y
+
+COM2W0_Periodically:
+  ldi yl, LOW(com2w0_iface)
+  ldi yh, HIGH(com2w0_iface)
+  rcall com2wPeriodically
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0EnableClkIrq
+;
+; @clobbers 
+
+com2w0EnableClkIrq:
+  push r16
+    inr r16, COM_IRQ_ADDR_CLK0
+    sbr r16, (1<<COM_IRQ_BIT_CLK0)          ; enable pin change irq for CLK line
+    outr COM_IRQ_ADDR_CLK0, r16
+  pop r16
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0DisableClkIrq
+;
+; @clobbers none
+
+com2w0DisableClkIrq:
+  push r16
+    inr r16, COM_IRQ_ADDR_CLK0
+    cbr r16, (1<<COM_IRQ_BIT_CLK0)        ; disable pin change irq for CLK line
+    outr COM_IRQ_ADDR_CLK0, r16
+  pop r16
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0ClkSetHigh
+;
+; @clobbers none
+
+com2w0ClkSetHigh:
+  cbi COM_CLK0_DDR, COM_CLK0_PIN           ; set CLK as input
+.ifdef COM_CLK0_PUE
+;  cbi COM_CLK0_PUE, COM_CLK0_PIN           ; disable pullup on CLK
+.else
+  cbi COM_CLK0_OUTPUT, COM_CLK0_PIN        ; disable pullup on CLK
+.endif
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0ClkSetLow
+;
+; @clobbers none
+
+com2w0ClkSetLow:
+  sbi COM_CLK0_DDR, COM_CLK0_PIN          ; set CLK as output
+  cbi COM_CLK0_OUTPUT, COM_CLK0_PIN       ; set CLK low
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0DataSetHigh
+;
+; @clobbers none
+
+com2w0DataSetHigh:
+  cbi COM_DATA0_DDR, COM_DATA0_PIN           ; set DATA as input
+.ifdef COM_DATA0_PUE
+;  cbi COM_DATA0_PUE, COM_CLK0_PIN           ; disable pullup on DATA
+.else
+  cbi COM_DATA0_OUTPUT, COM_DATA0_PIN        ; disable pullup on DATA
+.endif
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0DataSetLow
+;
+; @clobbers none
+
+com2w0DataSetLow:
+  sbi COM_DATA0_DDR, COM_DATA0_PIN          ; set DATA as output
+  cbi COM_DATA0_OUTPUT, COM_DATA0_PIN       ; set DATA low
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0ReadNextBit
+;
+; @clobbers r16, r17, r18, r20, r22
+
+com2w0ReadNextBit:
+;  ldi r20, 50                           ; wait for up to 250us for clock rise
+;  rcall com2w0WaitForClockHighMulti5Us  ; (R20, R22)
+;  brcc com2w0ReadNextBit_end
+  ; clock is high now, read bit
+  inr r17, COM_DATA0_INPUT
+  ; reset read timer (for leaving skipping mode)
+  clr r16
+  std Y+NET_IFACE_OFFS_READTIMER, r16
+  ; check mode
+  ldd r16, Y+COM2W_IFACE_OFFS_MODE
+  cpi r16, COM2W_MODE_READING
+  brne com2w0ReadNextBit_end
+  ; handle received bit
+  ldd r16, Y+COM2W_IFACE_OFFS_CURRBYTE
+  ldd r18, Y+COM2W_IFACE_OFFS_BITCOUNTER
+  andi r17, (1<<COM_DATA0_PIN)
+  clc
+  breq com2w0ReadNextBit_clockData
+  sec
+com2w0ReadNextBit_clockData:
+  ror r16
+  std Y+COM2W_IFACE_OFFS_CURRBYTE, r16
+  inc r18                                ; bit counter
+  std Y+COM2W_IFACE_OFFS_BITCOUNTER, r18
+  cpi r18, 8
+  brne com2w0ReadNextBit_end
+  ; write byte into buffer
+  push xl
+    push xh
+      rcall com2wByteRecvd               ; (r16, r17, r18, X)
+    pop xh
+  pop xl
+  ; prepare for next byte
+  clr r16
+  std Y+COM2W_IFACE_OFFS_BITCOUNTER, r16
+  std Y+COM2W_IFACE_OFFS_CURRBYTE, r16
+com2w0ReadNextBit_end:
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0WaitForClockHighMulti5Us
+;
+; Wait for high CLK
+;
+; @param  R20 multiple of 5us to wait (e.g. "2" for "10" us, max: 64)
+; @return CFLAG set if okay (state reached), cleared on error
+; @clobbers: r20, r22
+
+com2w0WaitForClockHighMulti5Us:
+.if clock == 8000000
+  add r20, r20 ; *2
+  add r20, r20 ; *4
+  add r20, r20 ; *8
+.endif
+.elif clock == 1000000
+; nothing to do
+.else
+  .error "Unhandled clock speed"
+.endif
+
+com2w0WaitForClockHighMulti5Us_loop:                   ; 5 cycles per loop
+    sbic COM_CLK0_INPUT, COM_CLK0_PIN                  ; +2 if skipped, +1 if not
+      rjmp com2w0WaitForClockHighMulti5Us_stateReached ; +2
+    dec r20                                            ; +1
+  brne com2w0WaitForClockHighMulti5Us_loop             ; +2
+  clc                                                  ; +1
+  ret                                                  ; +4
+com2w0WaitForClockHighMulti5Us_stateReached:
+  sec                                                  ; +1
+  ret                                                  ; +4
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0WaitForClockLowMulti5Us
+;
+; Wait for low CLK
+;
+; @param  R20 multiple of 5us to wait (e.g. "2" for "10" us, max: 64)
+; @return CFLAG set if okay (state reached), cleared on error
+; @clobbers: r20, r22
+
+com2w0WaitForClockLowMulti5Us:
+.if clock == 8000000
+  add r20, r20 ; *2
+  add r20, r20 ; *4
+  add r20, r20 ; *8
+.endif
+.elif clock == 1000000
+; nothing to do
+.else
+  .error "Unhandled clock speed"
+.endif
+
+com2w0WaitForClockLowMulti5Us_loop:                    ; 5 cycles per loop
+    sbis COM_CLK0_INPUT, COM_CLK0_PIN                  ; +2 if skipped, +1 if not
+      rjmp com2w0WaitForClockLowMulti5Us_stateReached  ; +2
+    dec r20                                            ; +1
+  brne com2w0WaitForClockLowMulti5Us_loop              ; +2
+  clc                                                  ; +1
+  ret                                                  ; +4
+com2w0WaitForClockLowMulti5Us_stateReached:
+  sec                                                  ; +1
+  ret                                                  ; +4
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0SendMsg
+;
+; @param X pointer to bytes to send
+; @param Y pointer to interface data in SRAM
+; @return CFLAG set if message sent, cleared otherwise
+; @clobbers R16, R18 (R20, R22, R24, R25, X)
+
+com2w0SendMsg:
+  ldi r20, 11                            ; wait for about 55us for clock low
+  rcall com2w0WaitForClockLowMulti5Us
+  brcs com2w0SendMsg_busy                ; CLK got low while waiting, so line is busy
+  push r15
+    in r15, SREG
+    cli                                  ; atomic disable irq and set CLK low
+    rcall com2w0DisableClkIrq            ; (none)
+    rcall com2w0ClkSetLow                ; reserve bus (none)
+    out SREG, r15
+  pop r15
+  adiw xh:xl, NETMSG_OFFS_MSGLEN
+  ld r18, X
+  sbiw xh:xl, NETMSG_OFFS_MSGLEN
+  inc r18                                ; adjust for DESTADDR
+  inc r18                                ; adjust for MSGLEN
+  inc r18                                ; adjust for CRCBYTE
+  rcall com2wWaitTime1                   ; longer wait period (R22)
+  rcall com2w0SendBytes                  ; (r16, r17, r18, r22, X)
+  rcall com2w0ClkSetHigh                 ; make sure bus is released
+  rcall com2w0DataSetHigh
+
+  rcall com2w0EnableClkIrq               ; (none)
+  ldi r16, NET_IFACE_OFFS_PACKETSOUT_LOW
+  rcall NET_Interface_IncCounter16       ; (R24, R25)
+  sec
+  ret
+com2w0SendMsg_busy:
+  ldi r16, NET_IFACE_OFFS_ERR_BUSY_LOW
+  rcall NET_Interface_IncCounter16       ; (R24, R25)
+  clc
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0SendBytes
+;
+; @param  R18 number of bytes to send
+; @param X pointer to bytes to send
+; @param Y pointer to interface data in SRAM
+; @clobbers: r16, r18, X (r17, r22)
+
+com2w0SendBytes:
+com2w0SendBytes_loop:
+    rcall com2w0ClkSetLow                     ; (none)
+    rcall com2wWaitTime1                      ; longer wait period (R22)
+    ld r16, X+
+    rcall com2w0SendByte                      ; (R16, R17, R22)
+    dec r18
+  brne com2w0SendBytes_loop
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0SendByte
+;
+; @param  R16 byte to send
+; @clobbers: r16, r17 (r22)
+
+com2w0SendByte:
+  ldi r17, 8
+com2w0SendByte_loop:
+    rcall com2w0ClkSetLow
+    rcall com2wWaitTime1                        ; longer wait period (R22)
+    lsr r16
+    brcs com2w0SendByte_send1
+    rcall com2w0DataSetLow
+    rjmp com2w0SendByte_sent
+com2w0SendByte_send1:
+    rcall com2w0DataSetHigh
+com2w0SendByte_sent:
+    rcall com2wWaitTime2                        ; shorter wait period (R22)
+    push r15
+      in r15, SREG
+      cli                                       ; ensure time period by disabling irqs
+      rcall com2w0ClkSetHigh
+      rcall com2wWaitTime1                      ; longer wait period (R22)
+      out SREG, r15
+    pop r15
+    dec r17
+  brne com2w0SendByte_loop
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine COM2W0_Run @global
+;
+; @return CFLAG set if something done, cleared otherwise
+; @clobbers all
+
+COM2W0_Run:
+  ldi yl, LOW(com2w0_iface)
+  ldi yh, HIGH(com2w0_iface)
+  rjmp com2w0RunMode          ; (all but Y)
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0RunMode
+;
+; @clobbers all
+
+com2w0RunMode:
+  cpi r16, COM2W_MODE_NUM
+  brcs COM2W0_Run_jump
+  ldi r16, COM2W_MODE_IDLE              ; unknown mode, set to idle
+  rcall com2wSetMode                    ; (R17)
+  sec
+  ret
+COM2W0_Run_jump:
+  ldi zl, LOW(com2w0ModeJumpTable)
+  ldi zh, HIGH(com2w0ModeJumpTable)
+  add zl, r16
+  adc zh, r16
+  sub zh, r16
+  ijmp
+com2w0ModeJumpTable:
+  rjmp com2w0RunIdle
+  rjmp com2w0RunReading
+  rjmp com2w0RunSkipping
+  rjmp com2w0RunWriting
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0RunIdle
+;
+; @param Y pointer to interface data in SRAM
+; @clobbers R16, R17, R22, R24, R25, X
+
+com2w0RunIdle:
+rjmp com2w0RunIdle_end ; DEBUG
+  push r15
+    in r15, SREG
+    cli
+    ; look for outbound message
+    rcall NET_Interface_PeekNextOutgoingMsgNum ; r16=msgNum
+    brcs com2w0RunIdle_haveMsg
+    out SREG, r15
+  pop r15
+  clc
+  rjmp com2w0RunIdle_end
+
+com2w0RunIdle_haveMsg:
+    mov r24, r16
+    ldi r16, COM2W_MODE_WRITING
+    rcall com2wSetMode                         ; (R17)
+    mov r16, r24
+    out SREG, r15
+  pop r15
+
+  push r16
+    rcall NET_Buffer_Locate                    ; (R17)
+    adiw xh:xl, 1
+    rcall com2w0SendMsg                        ; (R16, R17, R22, R24, R25, X)
+    push r15                           
+      inr r15, SREG                            ; save SREG (no CLI, we want to save CFLAG only)
+      ldi r16, COM2W_MODE_IDLE
+      rcall com2wSetMode                       ; (R17)
+      out SREG, r15                            ; restore SREG
+    pop r15
+  pop r16
+  brcc com2w0RunIdle_end
+
+  push r15
+    in r15, SREG
+    cli
+    rcall NET_Interface_GetNextOutgoingMsgNum  ; take current msg off the queue
+    rcall NET_Buffer_ReleaseByNum              ; (R16, X)
+    out SREG, r15
+  pop r15
+  sec
+com2w0RunIdle_end:
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0RunReading
+;
+; @param Y pointer to interface data in SRAM
+; @clobbers none
+
+com2w0RunReading:
+  ; check for timeout (Y+NET_IFACE_OFFS_READTIMER)
+  ldd r16, Y+NET_IFACE_OFFS_READTIMER
+  cpi r16, COM2W_READING_MAXREADCOUNTER
+  brcc com2w0RunReading_goIdle
+  ldd r16, Y+COM2W_IFACE_OFFS_MODECOUNTER
+  cpi r16, COM2W_READING_MAXMODECOUNTER
+  brcc com2w0RunReading_goIdle
+  clc
+  rjmp com2w0RunReading_end
+com2w0RunReading_goIdle:
+  ldi r16, NET_IFACE_OFFS_ERR_IO_LOW
+  rcall NET_Interface_IncCounter16     ; (R24, R25)
+  ldi r16, COM2W_MODE_IDLE
+  rcall com2wSetMode                   ; (r17)
+  sec
+com2w0RunReading_end:
+  ret
+; @end
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0RunSkipping
+;
+; @param Y pointer to interface data in SRAM
+; @clobbers r16 (r17)
+
+com2w0RunSkipping:
+  ; check for timeout (Y+NET_IFACE_OFFS_READTIMER)
+  ldd r16, Y+NET_IFACE_OFFS_READTIMER
+  cpi r16, COM2W_SKIPPING_MAXREADCOUNTER
+  brcc com2w0RunSkipping_goIdle
+  ldd r16, Y+COM2W_IFACE_OFFS_MODECOUNTER
+  cpi r16, COM2W_SKIPPING_MAXMODECOUNTER
+  brcc com2w0RunSkipping_goIdle
+  clc
+  rjmp com2w0RunSkipping_end
+com2w0RunSkipping_goIdle:
+  ldi r16, COM2W_MODE_IDLE
+  rcall com2wSetMode                   ; (r17)
+  sec
+com2w0RunSkipping_end:
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0RunWriting
+;
+; @param Y pointer to interface data in SRAM
+; @clobbers none
+
+com2w0RunWriting:
+  ; TODO: check for timeout
+  clc
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine COM2W0_ClkChangeIsr @global @isr
+;
+; @clobbers none
+
+COM2W0_ClkChangeIsr:
+  push r15
+    in r15, SREG
+    push r16
+      inr r16, COM_CLK0_INPUT                ; read clk state early
+      rcall COM2W0_HandleClockInterrupt
+    pop r16
+    out SREG, r15
+  pop r15
+  reti
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine COM2W0_HandleClockInterrupt @global
+;
+; @param r16 data from COM_CLKn_INPUT
+; @clobbers none
+
+COM2W0_HandleClockInterrupt:
+  push r16
+    push r17
+      push r18
+        push xl
+          push xh
+            push yl
+              push yh
+                ldi yl, LOW(com2w0_iface)
+                ldi yh, HIGH(com2w0_iface)
+                rcall com2w0ActOnClock       ; (r16, r17, r18, X)
+              pop yh
+            pop yl
+          pop xh
+        pop xl
+      pop r18
+    pop r17
+  pop r16
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine com2w0ActOnClock
+;
+; @param r16 data from COM_CLKn_INPUT
+; @clobbers r16 (r17, r18, X)
+
+com2w0ActOnClock:
+  andi r16, (1<<COM_CLK0_PIN)
+  brne com2w0ActOnClock_clockHigh
+  ; clock low
+  ldd r17, Y+COM2W_IFACE_OFFS_MODE
+  cpi r17, COM2W_MODE_IDLE
+  brne com2w0ActOnClock_end
+  rcall com2wStartReading           ; (r16, r17, X)
+  rjmp com2w0ActOnClock_end
+com2w0ActOnClock_clockHigh:
+  ldd r17, Y+COM2W_IFACE_OFFS_MODE
+  cpi r17, COM2W_MODE_READING
+  brne com2w0ActOnClock_end
+
+  push r20
+    push r22
+      rcall com2w0ReadNextBit            ; (r16, r17, r18, r20, r22)
+    pop r22
+  pop r20
+
+com2w0ActOnClock_end:
+  ret
+; @end
+
+
+
+
+
+#endif ; AVR_MODULES_COM2W_COM2W0_H
+