diff --git a/avr/lcd.asm b/avr/lcd.asm
index 35e8f97..0347f1a 100644
--- a/avr/lcd.asm
+++ b/avr/lcd.asm
@@ -1,5 +1,9 @@
-
-
+; ***************************************************************************
+; LCD module
+; (c) 2023 Martin Preuss
+;
+; Some code in this module is based on C-code in Tiny4kOLED (https://github.com/datacute/Tiny4kOLED/tree/master/src) 
+; by Stephen Denne (MIT license), rewritten in AVR assembler
 ;
 ; - page 0 is top line, page 7 ist bottom line
 ; - column 0 is the leftmost colum, column 127 is the rightmost column
@@ -20,16 +24,13 @@
 ; ***************************************************************************
 ; defines
 
-.equ LCD_CONTROLBYTE_DC_MASK = 0x40
-.equ LCD_CONTROLBYTE_CO_MASK = 0x80
-
 .equ LCD_TWI_ADDRESS         = 0x3c
 
 .equ LCD_WIDTH               = 128
 .equ LCD_HEIGHT              = 64
 
 .equ LCD_PAGE_COUNT          = 8
-.equ LCD_MULTIPLE            = 2
+
 .equ LCD_CMD_MODE            = 0x00
 .equ LCD_DATA_MODE           = 0x40
 
@@ -53,10 +54,16 @@ lcdDataEnd:
 
 
 
-LCD_Init:
- sbi DDRA, PORTA2 ; debug
- sbi PORTA, PORTA2 ; debug (off)
+; ---------------------------------------------------------------------------
+; LCD_Init
+;
+; IN:
+; - nothing
+; OUT:
+; - CFLAG: set if okay, clear on error
+; USED:
 
+LCD_Init:
   ldi zl, LOW(lcdInitCommandsBegin)
   ldi zh, HIGH(lcdInitCommandsBegin)
   ldi r16, 8
@@ -71,92 +78,50 @@ LCD_Init:
   ldi r16, 0
   rcall LCD_Fill
 
-  ldi r18, 0
+  ldi r18, 20
   ldi r19, 0
   rcall LCD_SetCursor
 
-  ldi zl, LOW(lcdHelloMsg1)
-  ldi zh, HIGH(lcdHelloMsg1)
+  ldi zl, LOW(lcdHelloMsg)
+  ldi zh, HIGH(lcdHelloMsg)
   rcall LCD_PrintFromFlash
 
-  ldi r18, 0
-  ldi r19, 2
-  rcall LCD_SetCursor
-
-  ldi zl, LOW(lcdHelloMsg2)
-  ldi zh, HIGH(lcdHelloMsg2)
-  rcall LCD_PrintFromFlash
-
-  ldi r18, 0
-  ldi r19, 4
-  rcall LCD_SetCursor
-
-  ldi zl, LOW(lcdHelloMsg3)
-  ldi zh, HIGH(lcdHelloMsg3)
-  rcall LCD_PrintFromFlash
-
-  ldi r18, 10
-  ldi r19, 5
-  rcall LCD_SetCursor
-
-  ldi zl, LOW(lcdHelloMsg4)
-  ldi zh, HIGH(lcdHelloMsg4)
-  rcall LCD_PrintFromFlash
-
-
   sec
   ret
 
 
 
+; ---------------------------------------------------------------------------
+; LCD_Fini
+;
+; IN:
+; - nothing
+; OUT:
+; - CFLAG: set if okay, clear on error
+; USED:
 
-; - R16: number of bytes to send
-; - Z=pointer to data
-lcdWriteCommandsFromFlash:
-  rcall twiStart
-  lsl zl
-  rol zh
-  mov r20, r16   ; number of bytes
-  ldi r16, (LCD_TWI_ADDRESS*2)
-  rcall twiSendByte
-  brcc lcdWriteCommandsFromFlash_error
-  tst r16
-  brne lcdWriteCommandsFromFlash_error
-  
-lcdWriteCommandsFromFlash_loop:
-    lpm r16, z+
-    rcall twiSendByte
-    brcc lcdWriteCommandsFromFlash_error
-    tst r16
-    brne lcdWriteCommandsFromFlash_error
-    dec r20
-  brne lcdWriteCommandsFromFlash_loop
-  rcall twiStop
- sbi DDRA, PORTA2 ; debug
- cbi PORTA, PORTA2 ; debug (on)
+LCD_Fini:
   sec
   ret
 
-lcdWriteCommandsFromFlash_error:
-  rcall twiStop
-  clc
-  ret
-
 
 
 ; ---------------------------------------------------------------------------
 ; LCD_SetCursor
 ;
-; Set cursor.
+; Set cursor. X is specified in pixels, Y is specified in character rows (8 pixels).
+; Left upper corner is 0/0 (x/y), right lower corner is 127/7
 ;
 ; IN:
 ; - R18: X
 ; - R19: Y
 ; OUT:
-; - nothing
+; - CFLAG: set if okay, cleared otherwise
 ; REGS: r1, r2, r16 (R16, R17, R18, R22)
 
 LCD_SetCursor:
+  in r15, SREG
+  cli
   mov r1, r18
   mov r2, r19
   rcall twiStart             ; (R22)
@@ -184,17 +149,31 @@ LCD_SetCursor:
   brcc LCD_SetCursor_error
 
   rcall twiStop              ; (R22)
+  out SREG, r15
   sec
   ret
 LCD_SetCursor_error:
   rcall twiStop              ; (R22)
+  out SREG, r15
   clc
   ret
 
 
 
+; ---------------------------------------------------------------------------
+; LCD_Fill
+;
+; Fill display RAM with the given value.
+;
+; IN:
 ; - R16: data to write
+; OUT:
+; - CFLAG: set if okay, cleared otherwise
+; REGS: r15, r16, r18, r19, r20, r21 (r17, r22)
+
 LCD_Fill:
+  in r15, SREG
+  cli
   mov r20, r16
 
   ldi r21, 0 ; Y
@@ -206,10 +185,10 @@ LCD_Fill_loopY:
 
     rcall twiStart
     ldi r16, (LCD_TWI_ADDRESS*2)
-    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    rcall twiSendByteExpectAck   ; (R16, R17, R18, R22)
     brcc LCD_Fill_error
     ldi r16, LCD_DATA_MODE
-    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    rcall twiSendByteExpectAck   ; (R16, R17, R18, R22)
     brcc LCD_Fill_error
   
     ldi r19, 0
@@ -225,14 +204,17 @@ LCD_Fill_loopX:
     inc r21
     cpi r21, LCD_PAGE_COUNT
   brcs LCD_Fill_loopY
+  out SREG, r15
   sec
   ret
 LCD_Fill_error:
   rcall twiStop
+  out SREG, r15
   clc
   ret
 
 
+
 ; ---------------------------------------------------------------------------
 ; LCD_PrintFromFlash
 ;
@@ -242,8 +224,11 @@ LCD_Fill_error:
 ; - Z: position of string to print
 ; OUT:
 ; - CFLAG: set if okay, cleared otherwise
-; REGS: 
+; REGS: r15, r16, Z (R17, R18, R22)
+
 LCD_PrintFromFlash:
+  in r15, SREG
+  cli
   lsl zl
   rol zh
   rcall twiStart
@@ -267,11 +252,13 @@ LCD_PrintFromFlash_loop:
   rjmp LCD_PrintFromFlash_loop
 LCD_PrintFromFlash_end:
   rcall twiStop
+  out SREG, r15
   sec
   ret
   
 LCD_PrintFromFlash_error:
   rcall twiStop
+  out SREG, r15
   clc
   ret
 
@@ -285,8 +272,11 @@ LCD_PrintFromFlash_error:
 ; IN:
 ; - R16: char
 ; OUT:
-; REGS: r16, r17, Z
+; REGS: r15, r16, r17, Z
+
 LCD_PrintChar:
+  in r15, SREG
+  cli
   rcall twiStart
   ldi r16, (LCD_TWI_ADDRESS*2)
   rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
@@ -298,10 +288,207 @@ LCD_PrintChar:
   rcall lcdPrintOneChar
   brcc LCD_PrintChar_error
   rcall twiStop
+  out SREG, r15
   sec
   ret
-  
 LCD_PrintChar_error:
+  rcall twiStop
+  out SREG, r15
+  clc
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; LCD_PrintHexByte
+;
+; Convert a give byte into HEX and write it to the current position.
+;
+; IN:
+; - R16: byte to convert to hex
+; OUT:
+; REGS: r15, r16, r17, Z
+
+LCD_PrintHexByte:
+  in r15, SREG
+  cli
+  mov r20, r16
+  rcall twiStart
+  ldi r16, (LCD_TWI_ADDRESS*2)
+  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+  brcc LCD_PrintHexByte_error
+  ldi r16, LCD_DATA_MODE
+  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+  brcc LCD_PrintHexByte_error
+  mov r16, r20
+  rcall lcdPrintHexByte
+  brcc LCD_PrintHexByte_error
+  rcall twiStop
+  out SREG, r15
+  sec
+  ret
+LCD_PrintHexByte_error:
+  rcall twiStop
+  out SREG, r15
+  clc
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; LCD_PrintHexWord
+;
+; Convert a give word into HEX and write it to the current position.
+;
+; IN:
+; - r18: low byte of the word
+; - r19: high byte of the word
+; OUT:
+; - CFLAG: set if okay, cleared otherwise
+; REGS: r15, r16, r17, Z
+
+LCD_PrintHexWord:
+  in r15, SREG
+  cli
+  push r18
+    push r19
+      rcall twiStart
+      ldi r16, (LCD_TWI_ADDRESS*2)
+      rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+      brcc LCD_PrintHexWord_error
+      ldi r16, LCD_DATA_MODE
+      rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+      brcc LCD_PrintHexWord_error
+    pop r19
+  pop r18
+    
+  rcall lcdPrintHexWord
+  brcc LCD_PrintHexWord_error
+  rcall twiStop
+  out SREG, r15
+  sec
+  ret
+LCD_PrintHexWord_error:
+      rcall twiStop
+    pop r19
+  pop r18
+  out SREG, r15
+  clc
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; lcdPrintHexWord
+;
+; Convert a give word into HEX and write it to the current position.
+;
+; IN:
+; - r18: low byte of the word
+; - r19: high byte of the word
+; OUT:
+; - CFLAG: set if okay, cleared otherwise
+
+lcdPrintHexWord:
+  mov r16, r19
+  push r18
+    rcall lcdPrintHexByte
+  pop r18
+  brcc lcdPrintHexWord_error
+  mov r16, r18
+  rcall lcdPrintHexByte
+  brcc lcdPrintHexWord_error
+  sec
+  ret
+lcdPrintHexWord_error:
+  clc
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; lcdPrintHexByte
+;
+; Convert a give byte into HEX and write it to the current position.
+;
+; IN:
+; - R16: byte to convert to hex
+; OUT:
+; - CFLAG: set if okay, cleared otherwise
+; REGS: r16, r20 (r16, r17)
+
+lcdPrintHexByte:
+  mov r20, r16
+  swap r16
+  rcall lcdNibbleToAscii ; write high nibble (r16, r17)
+  rcall lcdPrintOneChar  ; (r16, r17, Z)
+  brcc lcdPrintHexByte_error
+  mov r16, r20
+  rcall lcdNibbleToAscii ; write low nibble
+  rcall lcdPrintOneChar
+  brcc lcdPrintHexByte_error
+  sec
+  ret
+lcdPrintHexByte_error:
+  clc
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; lcdNibbleToAscii
+;
+; Convert a nibble to an ASCII char.
+; IN:
+; - R16: byte (in bits 0-3)
+; OUT:
+; - R16: ASCII representation of that nibble (e.g. '0' for 0)
+; REGS: r16, r17
+
+lcdNibbleToAscii:
+  andi r16, 0xf
+  cpi r16, 10
+  brcs lcdNibbleToAscii_l1
+  ldi r17, 7
+  add r16, r17
+lcdNibbleToAscii_l1:
+  ldi r17, '0'
+  add r16, r17
+  ret
+
+
+
+; ---------------------------------------------------------------------------
+; lcdWriteCommandsFromFlash
+;
+; IN:
+; - R16: number of bytes to send
+; - Z=pointer to data
+; OUT:
+; - CFLAG: set if okay, cleared otherwise
+
+; REGS: r16, r20, Z (r17, r18, r22)
+
+lcdWriteCommandsFromFlash:
+  rcall twiStart
+  lsl zl
+  rol zh
+  mov r20, r16                            ; number of bytes
+  ldi r16, (LCD_TWI_ADDRESS*2)
+  rcall twiSendByteExpectAck              ; (R16, R17, R18, R22)
+  brcc lcdWriteCommandsFromFlash_error
+  
+lcdWriteCommandsFromFlash_loop:
+    lpm r16, z+
+    rcall twiSendByteExpectAck            ; (R16, R17, R18, R22)
+    brcc lcdWriteCommandsFromFlash_error
+    dec r20
+  brne lcdWriteCommandsFromFlash_loop
+  rcall twiStop                           ; (R22)
+  sec
+  ret
+
+lcdWriteCommandsFromFlash_error:
   rcall twiStop
   clc
   ret
@@ -316,10 +503,10 @@ LCD_PrintChar_error:
 ; IN:
 ; - R16: char
 ; OUT:
-; REGS: r16, r17, Z
+; REGS: r16, r19, Z (R17, R18, R22)
 
 lcdPrintOneChar:
-  rcall lcdGetCharMatrix
+  rcall lcdGetCharMatrix       ; (r16, r17, Z)
   ldi r16, 0                   ; spacing between chars
   rcall twiSendByteExpectAck   ; (R16, R17, R18, R22)
   brcc lcdPrintOneChar_error
@@ -348,6 +535,7 @@ lcdPrintOneChar_error:
 ; OUT:
 ; - Z: pos of character matrix (ready for LPM)
 ; REGS: r16, r17, Z
+
 lcdGetCharMatrix:
   cpi r16, 95+32
   brcc lcdGetCharMatrix_l1
@@ -378,17 +566,12 @@ lcdGetCharMatrix_l2:
 lcdInitCommandsBegin:  ; 28 bytes
    .db LCD_CMD_MODE, 0xa8, ((LCD_PAGE_COUNT*8)-1), 0x8d, 0x14, 0xaf, 0xa1, 0xc8
 lcdInitCommandsEnd:
-  .db 0xae, 0x00, 0x10, 0x40, 0x81, 0xcf, 0xa1, 0xc8
-  .db 0xa6, 0xa8, 0x3f, 0xd3, 0x00, 0xd5, 0x80, 0xd9
-  .db 0xf1, 0xda, 0x12, 0xdb, 0x40, 0x20, 0x02, 0x8d
-  .db 0x14, 0xa4, 0xa6, 0xaf
 
-lcdHelloMsg1: .db "ILD :-)", 0
-;lcdHelloMsg2: .db "1234567890ABCDEFGH", 0, 0
-lcdHelloMsg2: .db "ICH LIEBE DICH!", 0
-lcdHelloMsg3: .db "abcdefghijklmnopqr", 0, 0
-lcdHelloMsg4: .db "abcde", 0
+lcdHelloMsg: .db "AqHOME 2023", 0
 
+
+; font taken from Tiny4kOLED (https://github.com/datacute/Tiny4kOLED/tree/master/src) by Stephen Denne (MIT license),
+; original by Neven Boyanov
 lcdFont6x8:
   .db 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 ;   0 
   .db 0x00, 0x00, 0x00, 0x2f, 0x00, 0x00 ; ! 1