avr: started reworking COM module.

- sending and receiving now basically works again, but too often the
  read buffer is in use when trying to receive a message.

avr/lcd.asm

@@ -134,39 +134,42 @@ LCD_Fini:
 
 LCD_SetCursor:
   in r15, SREG
-  cli
-  mov r1, r18
-  mov r2, r19
-  rcall twiStart             ; (R22)
-  ldi r16, (LCD_TWI_ADDRESS*2)
-  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
-  brcc LCD_SetCursor_error
-
-  ldi r16, LCD_CMD_MODE
-  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
-  brcc LCD_SetCursor_error
-  mov r16, r2
-  andi r16, 0x07
-  ori r16, 0xb0              ; Set Page Start Address for Page Addressing Mode
-  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
-  brcc LCD_SetCursor_error
-  mov r16, r1                
-  andi r16, 0x0f             ; Set Lower Column Start Address
-  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
-  brcc LCD_SetCursor_error
-  mov r16, r1
-  swap r16
-  andi r16, 0x0f
-  ori r16, 0x10              ; Set Higher Column Start Address
-  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
-  brcc LCD_SetCursor_error
-
-  rcall twiStop              ; (R22)
+  push r15
+    cli
+    mov r1, r18
+    mov r2, r19
+    rcall twiStart             ; (R22)
+    ldi r16, (LCD_TWI_ADDRESS*2)
+    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    brcc LCD_SetCursor_error
+  
+    ldi r16, LCD_CMD_MODE
+    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    brcc LCD_SetCursor_error
+    mov r16, r2
+    andi r16, 0x07
+    ori r16, 0xb0              ; Set Page Start Address for Page Addressing Mode
+    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    brcc LCD_SetCursor_error
+    mov r16, r1                
+    andi r16, 0x0f             ; Set Lower Column Start Address
+    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    brcc LCD_SetCursor_error
+    mov r16, r1
+    swap r16
+    andi r16, 0x0f
+    ori r16, 0x10              ; Set Higher Column Start Address
+    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    brcc LCD_SetCursor_error
+  
+    rcall twiStop              ; (R22)
+  pop r15
   out SREG, r15
   sec
   ret
 LCD_SetCursor_error:
-  rcall twiStop              ; (R22)
+    rcall twiStop              ; (R22)
+  pop r15
   out SREG, r15
   clc
   ret
@@ -295,23 +298,26 @@ LCD_PrintFromFlash_error:
 
 LCD_PrintChar:
   in r15, SREG
-  cli
-  rcall twiStart
-  ldi r16, (LCD_TWI_ADDRESS*2)
-  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
-  brcc LCD_PrintChar_error
-  ldi r16, LCD_DATA_MODE
-  rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
-  brcc LCD_PrintChar_error
-
-  rcall lcdPrintOneChar
-  brcc LCD_PrintChar_error
-  rcall twiStop
+  push r15
+    cli
+    rcall twiStart
+    ldi r16, (LCD_TWI_ADDRESS*2)
+    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    brcc LCD_PrintChar_error
+    ldi r16, LCD_DATA_MODE
+    rcall twiSendByteExpectAck ; (R16, R17, R18, R22)
+    brcc LCD_PrintChar_error
+  
+    rcall lcdPrintOneChar
+    brcc LCD_PrintChar_error
+    rcall twiStop
+  pop r15
   out SREG, r15
   sec
   ret
 LCD_PrintChar_error:
-  rcall twiStop
+    rcall twiStop
+  pop r15
   out SREG, r15
   clc
   ret