diff --git a/avr/att84_temp1.asm b/avr/att84_temp1.asm
index 9599901..183f7ae 100644
--- a/avr/att84_temp1.asm
+++ b/avr/att84_temp1.asm
@@ -42,6 +42,9 @@
 ; ---------------------------------------------------------------------------
 ; list of modules to use
 
+#define FW_MAIN_VERSION_HIGH 0
+#define FW_MAIN_VERSION_LOW  1
+
 #define MODULES_TIMER
 #define MODULES_COM
 #define MODULES_LED
@@ -49,6 +52,31 @@
 #define MODULES_LCD
 #define MODULES_SI7021
 
+.set MODULES_MASK = 0
+#ifdef MODULES_TIMER
+.set MODULES_MASK = MODULES_MASK | (1<<AQHOME_FW_MODULE_TIMER)
+#endif
+#ifdef MODULES_COM
+.set MODULES_MASK = MODULES_MASK | (1<<AQHOME_FW_MODULE_COM)
+#endif
+#ifdef MODULES_LED
+.set MODULES_MASK = MODULES_MASK | (1<<AQHOME_FW_MODULE_LED)
+#endif
+#ifdef MODULES_TWI_MASTER
+.set MODULES_MASK = MODULES_MASK | (1<<AQHOME_FW_MODULE_TWIMASTER)
+#endif
+#ifdef MODULES_LCD
+.set MODULES_MASK = MODULES_MASK | (1<<AQHOME_FW_MODULE_LCD)
+#endif
+#ifdef MODULES_SI7021
+.set MODULES_MASK = MODULES_MASK | (1<<AQHOME_FW_MODULE_SI7021)
+#endif
+
+
+
+; ---------------------------------------------------------------------------
+; defines for modules
+
 #define LCD_MINIMAL_FONT
 
 
@@ -211,19 +239,20 @@ ledA3Sram:   .byte LED_SRAM_SIZE
 .cseg
 
 ledA3Flash:    .db DDRA+0x20, PORTA+0x20, PINA+0x20, (1<<PORTA3)
-blinkPattern:  .db 2, 10, 0xff, 0xff   ; 1 short blink, 1s pause, restart
+blinkPattern:  .db 2, 50, 0xff, 0xff   ; 1 short blink, 2s pause, restart
 ;blinkPattern2: .db 10, 20, 0xff, 0xff   ; 1 long blink, 2s pause, restart
 
+firmwareHeader: .db FW_MAIN_VERSION_HIGH, FW_MAIN_VERSION_LOW
+                .dw MODULES_MASK
+
 
 .include "main.asm"
 
 
-
 ; ---------------------------------------------------------------------------
 ; Called on first time run, i.e. on system start. No arguments, no results.
 
 onSystemStart:
-  rcall Utils_SetupUid
 
 #ifdef MODULES_COM
   rcall CPRO_StartReclaimAddrProcedure
diff --git a/avr/defs.asm b/avr/defs.asm
index 176b597..25216d2 100644
--- a/avr/defs.asm
+++ b/avr/defs.asm
@@ -5,3 +5,11 @@
 .equ AQHOME_VALUETYPE_HUMIDITY = 2
 
 
+; module type ids for firmware header
+.equ AQHOME_FW_MODULE_TIMER     = 1
+.equ AQHOME_FW_MODULE_COM       = 2
+.equ AQHOME_FW_MODULE_LED       = 3
+.equ AQHOME_FW_MODULE_TWIMASTER = 4
+.equ AQHOME_FW_MODULE_LCD       = 5
+.equ AQHOME_FW_MODULE_SI7021    = 6
+