diff --git a/avr/devices/c01/defs.asm b/avr/devices/c01/defs.asm
index 21fed9d..ca34f21 100644
--- a/avr/devices/c01/defs.asm
+++ b/avr/devices/c01/defs.asm
@@ -67,6 +67,11 @@
 .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_DATA_DDR       = DDRD
+.equ COM_DATA_INPUT     = PIND
+.equ COM_DATA_OUTPUT    = PORTD
+.equ COM_DATA_PIN       = PORTD0
+
 .equ COM_ATTN_DDR       = DDRD
 .equ COM_ATTN_INPUT     = PIND
 .equ COM_ATTN_OUTPUT    = PORTD
diff --git a/avr/devices/c01/main/main.asm b/avr/devices/c01/main/main.asm
index db18bae..58b5e2f 100644
--- a/avr/devices/c01/main/main.asm
+++ b/avr/devices/c01/main/main.asm
@@ -56,7 +56,8 @@
 #define MODULES_LED_SIMPLE
 #define MODULES_NETWORK
 ;#define MODULES_COMONUART0
-#define MODULES_UART_HW
+;#define MODULES_UART_HW
+#define MODULES_UART_BITBANG
 #define MODULES_SPI_HW
 #define MODULES_ILI9341
 ;#define MODULES_FONT_8X8
@@ -117,7 +118,8 @@
 ; ---------------------------------------------------------------------------
 ; Reset and interrupt vectors
   rjmp BOOTLOADER_ADDR          ;  1: Reset vector   RESET
-  rjmp NetUart_AttnChangeIsr    ;  2: INT0           External Interrupt Request 0
+;  rjmp NetUart_AttnChangeIsr    ;  2: INT0           External Interrupt Request 0
+  rjmp UART_BitBang_PcintIsr
   reti                          ;  3: INT1           External Interrupt Request 1
   reti                          ;  4: TIMER1_CAPT    Timer/Counter1 Capture Event
   reti                          ;  5: TIMER1_COMPA   Timer/Counter1 Compare Match A
@@ -216,7 +218,8 @@ onEveryLoop:
 ; ---------------------------------------------------------------------------
 ; defines for network interface
 
-.equ netInterfaceData = netUartIface
+;.equ netInterfaceData = netUartIface
+.equ netInterfaceData = uart_bitbang_iface
 
 
 
diff --git a/avr/modules/uart_bitbang2/iface.asm b/avr/modules/uart_bitbang2/iface.asm
index 64ea27a..99167ee 100644
--- a/avr/modules/uart_bitbang2/iface.asm
+++ b/avr/modules/uart_bitbang2/iface.asm
@@ -55,12 +55,41 @@ UART_BitBang_Init:
   cbi COM_ATTN_OUTPUT, COM_ATTN_PIN       ; disable internal pullup for ATTN
 
   ; enable IRQ
+.ifdef INT0
+  .if COM_IRQ_BIT_ATTN == INT0
+    inr r16, MCUCR
+    cbr r16, (1<<ISC01) | (1<<ISC00)
+    sbr r16, (1<<ISC01) | (0<<ISC00)        ; falling edge of ATTN
+    outr MCUCR, r16
+  ;  sbr r16, (0<<ISC01) | (0<<ISC00)         ; low level triggers
+    inr r16, COM_IRQ_ADDR_ATTN             ; enable irq for ATTN line
+    sbr r16, (1<<COM_IRQ_BIT_ATTN)
+    outr COM_IRQ_ADDR_ATTN, r16
+  .else
+    sbi COM_IRQ_ADDR_ATTN, COM_IRQ_BIT_ATTN ; enable pin change irq for ATTN line
+    in r16, GIMSK                           ; enable pin change irq PCIE0 or PCIE1
+    ori r16, (1<<COM_IRQ_GIMSK_ATTN)
+    out GIMSK, R16
+    ldi r16, (1<<COM_IRQ_GIFR_ATTN)         ; clear pending irq by writing 1 to ATTN bit
+    out GIFR, r16
+  .endif
+.else
   sbi COM_IRQ_ADDR_ATTN, COM_IRQ_BIT_ATTN ; enable pin change irq for ATTN line
   in r16, GIMSK                           ; enable pin change irq PCIE0 or PCIE1
   ori r16, (1<<COM_IRQ_GIMSK_ATTN)
   out GIMSK, R16
   ldi r16, (1<<COM_IRQ_GIFR_ATTN)         ; clear pending irq by writing 1 to ATTN bit
   out GIFR, r16
+.endif
+
+#if 0
+  sbi COM_IRQ_ADDR_ATTN, COM_IRQ_BIT_ATTN ; enable pin change irq for ATTN line
+  in r16, GIMSK                           ; enable pin change irq PCIE0 or PCIE1
+  ori r16, (1<<COM_IRQ_GIMSK_ATTN)
+  out GIMSK, R16
+  ldi r16, (1<<COM_IRQ_GIFR_ATTN)         ; clear pending irq by writing 1 to ATTN bit
+  out GIFR, r16
+#endif
 
   sec
   ret
@@ -78,6 +107,7 @@ UART_BitBang_Fini:
   cbi COM_DATA_DDR, COM_DATA_PIN          ; set TXD port as input
   cbi COM_ATTN_DDR, COM_ATTN_PIN          ; set ATTN port as input
 
+#if 0
   cbi COM_IRQ_ADDR_ATTN, COM_IRQ_BIT_ATTN ; disable pin change irq for ATTN line
   in r16, GIMSK                           ; enable pin change irq PCIE0 or PCIE1
   andi r16, ~(1<<COM_IRQ_GIMSK_ATTN)
@@ -85,6 +115,8 @@ UART_BitBang_Fini:
   
   ldi r16, (1<<COM_IRQ_GIFR_ATTN)         ; clear pending irq by writing 1 to ATTN bit
   out GIFR, r16
+#endif
+
   ret
 ; @end