diff --git a/0BUILD b/0BUILD
index e0fc43b..4642c15 100644
--- a/0BUILD
+++ b/0BUILD
@@ -95,7 +95,7 @@
         </output>
 
         <cmd tool="$(avrdude)" checkDates="FALSE"  >
-          -p t84 -c stk500 -P /dev/ttyACM0 -B16 -U flash:w:avr/aqhomeavr.hex
+          -p t84 -c stk500 -P /dev/ttyACM0 -B16 -U flash:w:avr/att84_temp1.hex
         </cmd>
 
         <buildMessage>
diff --git a/avr/.gitignore b/avr/.gitignore
index e265a56..266d055 100644
--- a/avr/.gitignore
+++ b/avr/.gitignore
@@ -1,2 +1,3 @@
 main.obj
-main.eep.hex
+*.eep.hex
+*.obj
diff --git a/avr/0BUILD b/avr/0BUILD
index 4f3d1d3..5efda71 100644
--- a/avr/0BUILD
+++ b/avr/0BUILD
@@ -2,6 +2,7 @@
 
 <gwbuild>
 
+<!--
   <target type="AvrHexFile" name="aqhomeavr" >
 
     <includes type="avrasm" >
@@ -16,6 +17,24 @@
     </sources>
 
 
+  </target>
+-->
+
+
+  <target type="AvrHexFile" name="att84_temp1" >
+
+    <includes type="avrasm" >
+      -I $(builddir)
+      -I $(srcdir)
+      -I $(topsrcdir)/avr
+    </includes>
+
+
+    <sources type="avrasm" >
+      att84_temp1.asm
+    </sources>
+
+
   </target>
   
 </gwbuild>
diff --git a/avr/att84_temp1.asm b/avr/att84_temp1.asm
new file mode 100644
index 0000000..6144804
--- /dev/null
+++ b/avr/att84_temp1.asm
@@ -0,0 +1,401 @@
+; ***************************************************************************
+; Source file for temperature sensor node on AtTiny 84
+;
+; This is for the full system (i.e. not the boot loader).
+;
+; All definitions and changes should go into this file.
+;
+;
+;                                 AtTiny84
+;                                 --------
+;                            VCC  1     14  GND
+;                            PB0  2     13  PA0
+;                            PB1  3     12  PA1  COM-DATA
+;                  /RESET    PB3  4     11  PA2  OWI
+;                  KEY1      PB2  5     10  PA3  LED
+;                  COM_ATTN  PA7  6      9  PA4  TWI-SCL
+;                  TWI-SDA   PA6  7      8  PA5
+;                                 --------
+;
+; ***************************************************************************
+
+
+
+.nolist
+.include "include/tn84def.inc" ; Define device ATtiny84
+.list
+
+.include "defs.asm"
+
+
+
+; ***************************************************************************
+; defines
+
+; ---------------------------------------------------------------------------
+; generic
+
+.equ clock=1000000 ; Define the clock frequency
+
+
+
+; ---------------------------------------------------------------------------
+; list of modules to use
+
+#define MODULES_TIMER
+#define MODULES_COM
+#define MODULES_LED
+#define MODULES_TWI_MASTER
+#define MODULES_LCD
+#define MODULES_SI7021
+
+
+.equ VALUE_ID_TEMP1 = 0x01
+.equ VALUE_ID_HUM1  = 0x02
+
+
+
+; ---------------------------------------------------------------------------
+; COM module
+
+.equ COM_BIT_LENGTH      = 52000 ; 104000=9600, 52000=19200, 26000=38400
+
+.equ COM_DDR_DATA        = DDRA
+.equ COM_PORT_DATA       = PORTA
+.equ COM_PIN_DATA        = PINA
+.equ COM_PINNUM_DATA     = PORTA1
+
+.equ COM_DDR_ATTN        = DDRA
+.equ COM_PORT_ATTN       = PORTA
+.equ COM_PIN_ATTN        = PINA
+.equ COM_PINNUM_ATTN     = PORTA7
+
+.equ COM_IRQ_ADDR_ATTN   = PCMSK0
+.equ COM_IRQ_BIT_ATTN    = 7              ; bit 7 in PCMSK0
+.equ COM_IRQ_GIFR_ATTN   = PCIF0
+.equ COM_IRQ_GIMSK_ATTN  = PCIE0
+
+
+
+; ---------------------------------------------------------------------------
+; TWI master module
+
+.equ LCD_TWI_ADDRESS      = 0x3c
+
+.equ TWI_DDR_SCL          = DDRA
+.equ TWI_PORT_SCL         = PORTA
+.equ TWI_PIN_SCL          = PINA
+.equ TWI_PINNUM_SCL       = PORTA4
+
+.equ TWI_DDR_SDA          = DDRA
+.equ TWI_PORT_SDA         = PORTA
+.equ TWI_PIN_SDA          = PINA
+.equ TWI_PINNUM_SDA       = PORTA6
+
+
+
+; ---------------------------------------------------------------------------
+; BMP 280
+
+.equ BMP280_ADDR          = 0x76
+
+
+
+; ---------------------------------------------------------------------------
+; SI 7021
+
+.equ SI7021_ADDR          = 0x40
+
+
+
+
+
+; ***************************************************************************
+; code segment
+
+.cseg
+.org 000000
+
+
+
+; ---------------------------------------------------------------------------
+; Reset and interrupt vectors
+
+	rjmp main ; Reset vector
+	reti ; EXT_INT0
+	rjmp comIsrPcint0 ; PCI0
+	reti ; PCI1
+	reti ; WATCHDOG
+	reti ; ICP1
+	reti ; OC1A
+	reti ; OC1B
+	reti ; OVF1
+        rjmp timerIrqOC0A ; OC0A
+	reti ; OC0B
+	reti ; OVF0
+	reti ; ACI
+	reti ; ADCC
+	reti ; ERDY
+	reti ; USI_STR
+	reti ; USI_OVF
+
+
+
+; ***************************************************************************
+; includes
+
+.include "utils.asm"
+.include "timer.asm"
+.include "led.asm"
+.include "com.asm"
+.include "twimaster.asm"
+.include "lcd.asm"
+;.include "bmp280.asm"
+.include "si7021.asm"
+
+
+
+; ***************************************************************************
+; data in SRAM
+
+.dseg
+
+ledA3Sram:   .byte LED_SRAM_SIZE
+
+
+
+
+; ***************************************************************************
+; data in EEPROM
+
+.eseg
+
+
+
+
+; ***************************************************************************
+; data in FLASH
+
+.cseg
+
+ledA3Flash:    .db DDRA+0x20, PORTA+0x20, PINA+0x20, (1<<PORTA3)
+blinkPattern:  .db 5, 5, 5, 5, 5, 10, 0xff, 0xff   ; 3 short blinks, 1s pause, restart
+blinkPattern2:  .db 10, 20, 0xff, 0xff   ; 1 long blink, 2s pause, restart
+
+
+
+.include "main.asm"
+
+
+
+; ---------------------------------------------------------------------------
+; onEvery100ms
+;
+; Called every 100ms. Add your routine calls here.
+;
+; IN:
+; - nothing
+; OUT:
+; - nothing
+; USED: depending on called routines
+
+onEvery100ms:
+#ifdef MODULES_LED
+  ; ticker for LED module
+  ldi zl, LOW(ledA3Flash)
+  ldi zh, HIGH(ledA3Flash)
+  ldi yl, LOW(ledA3Sram)
+  ldi yh, HIGH(ledA3Sram)
+  rcall Led_Tick
+#endif
+
+  ; add more calls here
+  
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; onEverySecond
+;
+; Called every second. Add your routine calls here.
+;
+; IN:
+; - nothing
+; OUT:
+; - nothing
+; USED: depending on called routines
+
+onEverySecond:
+;  rcall TWI_Master_ScanNext
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; onEvery10s
+;
+; Called every 10 seconds. Add your routine calls here.
+;
+; IN:
+; - nothing
+; OUT:
+; - nothing
+; USED: depending on called routines
+
+onEvery10s:
+  rcall printSendStats
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; onEvery30s
+;
+; Called every 10 seconds. Add your routine calls here.
+;
+; IN:
+; - nothing
+; OUT:
+; - nothing
+; USED: depending on called routines
+
+onEvery30s:
+#ifdef MODULES_SI7021
+  rcall SI7021_PeriodicMeasurement
+  rcall sendValueMsg
+#endif
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; onEveryMinute
+;
+; Called every minute. Add your routine calls here.
+;
+; IN:
+; - nothing
+; OUT:
+; - nothing
+; USED: depending on called routines
+
+onEveryMinute:
+  in r15, SREG ; debug
+  cli
+  push r15
+
+#ifdef MODULES_COM
+    ldi r16, 219
+    rcall COM_EnqueueComSendStats
+
+    ;ldi r16, 219
+    ;rcall COM_EnqueuePing
+#endif
+
+  pop r15
+  out SREG, r15
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; onPacketReceived:
+;
+; Called after a packet was received via COM module. Add your routine calls here.
+;
+; The packet will be removed from buffer in any case after return from this call.
+; IN:
+; - Y  : pointer to received buffer
+; OUT:
+; - CFLAG: set if handled, cleared otherwise
+; USED: depending on called routines
+
+onPacketReceived:
+  clc               ; not handled
+  ret
+
+
+
+
+
+
+#ifdef MODULES_COM
+debugSendByte:
+  push r15
+    in r15, SREG ; debug
+    cli
+    push r17
+      push r22
+        ldi r17, 8
+        sbi DDRA, PORTA2 ; debug
+        
+        cbi PORTA, PORTA2 ; debug (on)
+        Utils_WaitNanoSecs 100000, 0, r22 ; start with 2t low
+
+        sbi PORTA, PORTA2 ; debug (off)
+        nop
+        nop
+        cbi PORTA, PORTA2 ; debug (on)
+        Utils_WaitNanoSecs 100000, 0, r22 ; start with 2t low
+        
+        debugSendByte_loop:
+        lsr r16
+        brcs debugSendByte_sendLow
+        cbi PORTA, PORTA2 ; debug (on)
+        rjmp debugSendByte_wait
+        debugSendByte_sendLow:
+        sbi PORTA, PORTA2 ; debug (off)
+        
+        debugSendByte_wait:
+        Utils_WaitNanoSecs 100000, 0, r22
+        dec r17
+        brne debugSendByte_loop
+        
+        cbi PORTA, PORTA2 ; debug (on)
+        Utils_WaitNanoSecs 200000, 0, r22 ; end with 2t low
+        sbi PORTA, PORTA2 ; debug (off)
+      pop r22
+    pop r17
+    out SREG, r15
+  pop r15
+  ret
+#endif
+
+
+
+sendValueMsg:
+  ; send message for current temp
+  lds r22, si7021Flags
+  mov r16, r22
+  andi r16, SI7021_FLAGS_TEMP_VALID
+  breq sendValueMsg_checkHum
+  ldi r16, 0xff                      ; destination address
+  ldi r17, VALUE_ID_TEMP1            ; value id
+  ldi r22, AQHOME_VALUETYPE_TEMP
+  lds r18, si7021LastTemp            ; value
+  lds r19, si7021LastTemp+1
+  ldi r20, 100                       ; denominator
+  clr r21
+  push r22
+    rcall COM_EnqueueValue
+  pop r22
+sendValueMsg_checkHum:
+  mov r16, r22
+  andi r16, SI7021_FLAGS_HUM_VALID
+  breq sendValueMsg_done
+  ldi r16, 0xff                      ; destination address
+  ldi r17, VALUE_ID_HUM1             ; value id
+  ldi r22, AQHOME_VALUETYPE_HUMIDITY
+  lds r18, si7021LastHumidity        ; value
+  lds r19, si7021LastHumidity+1
+  ldi r20, 1                         ; denominator
+  clr r21
+  push r22
+    rcall COM_EnqueueValue
+  pop r22
+sendValueMsg_done:
+  ret
+
+
+
diff --git a/avr/defs.asm b/avr/defs.asm
new file mode 100644
index 0000000..176b597
--- /dev/null
+++ b/avr/defs.asm
@@ -0,0 +1,7 @@
+
+
+
+.equ AQHOME_VALUETYPE_TEMP     = 1
+.equ AQHOME_VALUETYPE_HUMIDITY = 2
+
+
diff --git a/avr/main.asm b/avr/main.asm
index a18b323..9d3307a 100644
--- a/avr/main.asm
+++ b/avr/main.asm
@@ -1,138 +1,6 @@
-.nolist
-.include "include/tn84def.inc" ; Define device ATtiny84
-.list
 
 
-
-; ***************************************************************************
-; defines
-
-; ---------------------------------------------------------------------------
-; generic
-
-.equ clock=1000000 ; Define the clock frequency
-
-
-
-; ---------------------------------------------------------------------------
-; COM module
-
-.equ COM_BIT_LENGTH      = 52000 ; 104000=9600, 52000=19200, 26000=38400
-
-.equ COM_DDR_DATA        = DDRA
-.equ COM_PORT_DATA       = PORTA
-.equ COM_PIN_DATA        = PINA
-.equ COM_PINNUM_DATA     = PORTA1
-
-.equ COM_DDR_ATTN        = DDRA
-.equ COM_PORT_ATTN       = PORTA
-.equ COM_PIN_ATTN        = PINA
-.equ COM_PINNUM_ATTN     = PORTA7
-
-.equ COM_IRQ_ADDR_ATTN   = PCMSK0
-.equ COM_IRQ_BIT_ATTN    = 7              ; bit 7 in PCMSK0
-.equ COM_IRQ_GIFR_ATTN   = PCIF0
-.equ COM_IRQ_GIMSK_ATTN  = PCIE0
-
-
-
-; ---------------------------------------------------------------------------
-; TWI master module
-
-.equ LCD_TWI_ADDRESS      = 0x3c
-
-.equ TWI_DDR_SCL          = DDRA
-.equ TWI_PORT_SCL         = PORTA
-.equ TWI_PIN_SCL          = PINA
-.equ TWI_PINNUM_SCL       = PORTA4
-
-.equ TWI_DDR_SDA          = DDRA
-.equ TWI_PORT_SDA         = PORTA
-.equ TWI_PIN_SDA          = PINA
-.equ TWI_PINNUM_SDA       = PORTA6
-
-
-
-
-; ---------------------------------------------------------------------------
-; BMP 280
-
-.equ BMP280_ADDR          = 0x76
-
-
-; ***************************************************************************
-; code segment
-
 .cseg
-.org 000000
-
-
-
-; ---------------------------------------------------------------------------
-; Reset and interrupt vectors
-
-	rjmp main ; Reset vector
-	reti ; EXT_INT0
-	rjmp comIsrPcint0 ; PCI0
-	reti ; PCI1
-	reti ; WATCHDOG
-	reti ; ICP1
-	reti ; OC1A
-	reti ; OC1B
-	reti ; OVF1
-        rjmp timerIrqOC0A ; OC0A
-	reti ; OC0B
-	reti ; OVF0
-	reti ; ACI
-	reti ; ADCC
-	reti ; ERDY
-	reti ; USI_STR
-	reti ; USI_OVF
-
-
-
-; ***************************************************************************
-; includes
-
-.include "utils.asm"
-.include "timer.asm"
-.include "led.asm"
-.include "com.asm"
-.include "twimaster.asm"
-.include "lcd.asm"
-.include "bmp280.asm"
-
-
-
-; ***************************************************************************
-; data in SRAM
-
-.dseg
-
-ledA3Sram:   .byte LED_SRAM_SIZE
-
-
-
-
-; ***************************************************************************
-; data in EEPROM
-
-.eseg
-
-
-
-
-; ***************************************************************************
-; data in FLASH
-
-.cseg
-
-ledA3Flash:    .db DDRA+0x20, PORTA+0x20, PINA+0x20, (1<<PORTA3)
-blinkPattern:  .db 5, 5, 5, 5, 5, 10, 0xff, 0xff   ; 3 short blinks, 1s pause, restart
-blinkPattern2:  .db 10, 20, 0xff, 0xff   ; 1 long blink, 2s pause, restart
-
-
-
 
 
 main:
@@ -190,18 +58,36 @@ main_loop:
 ; USED: depending on called routines
 
 initModules:
+#ifdef MODULES_TIMER
   rcall Timer_Init
+#endif
 
+#ifdef MODULES_LED
   ldi zl, LOW(ledA3Flash)
   ldi zh, HIGH(ledA3Flash)
   ldi yl, LOW(ledA3Sram)
   ldi yh, HIGH(ledA3Sram)
   rcall Led_Init
+#endif
   
+#ifdef MODULES_COM
   rcall Com_Init
+#endif
+#ifdef MODULES_TWI_MASTER
   rcall TWI_Master_Init
+#endif
+#ifdef MODULES_LCD
   rcall LCD_Init
+#endif
+#ifdef MODULES_BMP280
   rcall BMP280_Init
+#endif
+
+#ifdef MODULES_SI7021
+  rcall SI7021_Init
+#endif
+
+  ; done
   ret
 
 
@@ -219,9 +105,12 @@ initModules:
 
 runModulesUntilIdle:
 
+#ifdef MODULES_TIMER
   ; TIMER module
   rcall Timer_Run
+#endif
 
+#ifdef MODULES_COM
   ; COM module (call until carry flag cleared but at most 10 times to not starve other modules)
   ldi r16, 10
 runModulesUntilIdle_Com:
@@ -232,158 +121,13 @@ runModulesUntilIdle_Com:
     dec r16
   brne runModulesUntilIdle_Com
 runModulesUntilIdle_ComEnd:
+#endif
 
   ; add more modules here
   ret
 
 
 
-; ---------------------------------------------------------------------------
-; onEvery100ms
-;
-; Called every 100ms. Add your routine calls here.
-;
-; IN:
-; - nothing
-; OUT:
-; - nothing
-; USED: depending on called routines
-
-onEvery100ms:
-  ; ticker for LED module
-  ldi zl, LOW(ledA3Flash)
-  ldi zh, HIGH(ledA3Flash)
-  ldi yl, LOW(ledA3Sram)
-  ldi yh, HIGH(ledA3Sram)
-  rcall Led_Tick
-
-  ; add more calls here
-  
-  ret
-
-
-
-; ---------------------------------------------------------------------------
-; onEverySecond
-;
-; Called every second. Add your routine calls here.
-;
-; IN:
-; - nothing
-; OUT:
-; - nothing
-; USED: depending on called routines
-
-onEverySecond:
-;  rcall TWI_Master_ScanNext
-  ret
-
-
-
-; ---------------------------------------------------------------------------
-; onEvery10s
-;
-; Called every 10 seconds. Add your routine calls here.
-;
-; IN:
-; - nothing
-; OUT:
-; - nothing
-; USED: depending on called routines
-
-onEvery10s:
-  ret
-
-
-
-; ---------------------------------------------------------------------------
-; onEveryMinute
-;
-; Called every minute. Add your routine calls here.
-;
-; IN:
-; - nothing
-; OUT:
-; - nothing
-; USED: depending on called routines
-
-onEveryMinute:
-  in r15, SREG ; debug
-  cli
-  push r15
-    ldi r16, 219
-    rcall COM_EnqueueComSendStats
-    rcall printSendStats
-
-    ;ldi r16, 219
-    ;rcall COM_EnqueuePing
-  pop r15
-  out SREG, r15
-  ret
-
-
-
-; ---------------------------------------------------------------------------
-; onPacketReceived:
-;
-; Called after a packet was received via COM module. Add your routine calls here.
-;
-; The packet will be removed from buffer in any case after return from this call.
-; IN:
-; - Y  : pointer to received buffer
-; OUT:
-; - CFLAG: set if handled, cleared otherwise
-; USED: depending on called routines
-
-onPacketReceived:
-  clc               ; not handled
-  ret
-
-
-
-
-
-
-
-debugSendByte:
-  push r15
-    in r15, SREG ; debug
-    cli
-    push r17
-      push r22
-        ldi r17, 8
-        sbi DDRA, PORTA2 ; debug
-        
-        cbi PORTA, PORTA2 ; debug (on)
-        Utils_WaitNanoSecs 100000, 0, r22 ; start with 2t low
-
-        sbi PORTA, PORTA2 ; debug (off)
-        nop
-        nop
-        cbi PORTA, PORTA2 ; debug (on)
-        Utils_WaitNanoSecs 100000, 0, r22 ; start with 2t low
-        
-        debugSendByte_loop:
-        lsr r16
-        brcs debugSendByte_sendLow
-        cbi PORTA, PORTA2 ; debug (on)
-        rjmp debugSendByte_wait
-        debugSendByte_sendLow:
-        sbi PORTA, PORTA2 ; debug (off)
-        
-        debugSendByte_wait:
-        Utils_WaitNanoSecs 100000, 0, r22
-        dec r17
-        brne debugSendByte_loop
-        
-        cbi PORTA, PORTA2 ; debug (on)
-        Utils_WaitNanoSecs 200000, 0, r22 ; end with 2t low
-        sbi PORTA, PORTA2 ; debug (off)
-      pop r22
-    pop r17
-    out SREG, r15
-  pop r15
-  ret
 
 
 
@@ -392,6 +136,29 @@ printSendStats:
   push r15
     in r15, SREG ; debug
     cli
+
+#ifdef MODULES_SI7021
+    ldi r18, 0
+    ldi r19, 1
+    rcall LCD_SetCursor
+    ldi zl, LOW(textSi7021Firmware)
+    ldi zh, HIGH(textSi7021Firmware)
+    rcall LCD_PrintFromFlash
+
+    lds r16, si7021Flags
+    rcall LCD_PrintHexByte
+    ldi r16, 32
+    rcall LCD_PrintChar
+    lds r18, si7021LastTemp
+    lds r19, si7021LastTemp+1
+    rcall LCD_PrintHexWord
+    ldi r16, 32
+    rcall LCD_PrintChar
+    lds r18, si7021LastHumidity
+    lds r19, si7021LastHumidity+1
+    rcall LCD_PrintHexWord
+#endif
+
     ldi r18, 0
     ldi r19, 2
     rcall LCD_SetCursor
@@ -448,6 +215,7 @@ printSendStats:
   
 
 
+textSi7021Firmware:      .db "SI: ", 0, 0
 textStatsPacketsIn:      .db "In     : ", 0
 textStatsPacketsRecvErr: .db "RecvErr: ", 0
 textStatsPacketsOut:     .db "Out    : ", 0
@@ -455,3 +223,5 @@ textStatsCollisions:     .db "Coll   : ", 0
 textStatsAborted:        .db "Aborted: ", 0
 
 
+
+