diff --git a/avr/devices/t03/boot.asm b/avr/devices/t03/boot.asm
index 870c910..3f3d730 100644
--- a/avr/devices/t03/boot.asm
+++ b/avr/devices/t03/boot.asm
@@ -245,3 +245,97 @@ debugWriteString_done:
 debugString: .db "Hello", 13, 10, 0
 
 
+
+debugPrintLoop:
+  sbi LED_PORT, LED_PINNUM ; off
+  ; enable transceiver
+  lds r17, UCSR1B
+;  cbr r17, (1<<UDRIE1)  ; disable DRE interrupt
+  ori r17, (1<<RXEN1) | (1<<TXEN1)   ; enable transmit and receive
+  sts UCSR1B, r17
+
+debugPrintLoop1:
+  push r16
+    rcall debugPrintHexByte
+    ldi r16, 13
+    rcall debugPrintOneChar    ; (r17)
+    ldi r16, 10
+    rcall debugPrintOneChar    ; (r17)
+    ldi r16, 10
+    rcall flashWaitForMulti100ms
+  pop r16
+  rjmp debugPrintLoop1
+
+
+
+; ---------------------------------------------------------------------------
+; @routine debugPrintHexByte
+;
+; Convert a give byte into HEX and write it to USART1.
+;
+; @return CFLAG set if okay, cleared on error
+; @param  R16 byte to convert to print
+; @clobbers r16, r20 (r17)
+
+debugPrintHexByte:
+  mov r20, r16
+  swap r16
+  rcall debugNibbleToAscii ; write high nibble (r17)
+  rcall debugPrintOneChar  ; (r17)
+  brcc debugPrintHexByte_error
+  mov r16, r20
+  rcall debugNibbleToAscii ; write low nibble (r17)
+  rcall debugPrintOneChar  ; (r17)
+  brcc debugPrintHexByte_error
+  sec
+  ret
+debugPrintHexByte_error:
+  clc
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine debugNibbleToAscii
+;
+; Convert a nibble to an ASCII char.
+; @return R16 ASCII representation of that nibble (e.g. '0' for 0)
+; @param  R16 byte (in bits 0-3)
+; @clobbers r17
+
+debugNibbleToAscii:
+  andi r16, 0xf
+  cpi r16, 10
+  brcs debugNibbleToAscii_l1
+  ldi r17, 7
+  add r16, r17
+debugNibbleToAscii_l1:
+  ldi r17, '0'
+  add r16, r17
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine debugPrintOneChar
+;
+; Write one byte to UART1.
+; @param  R16 byte to send
+; @clobbers r17
+
+debugPrintOneChar:
+    lds r17, UCSR1A
+    sbrs r17, UDRE1
+  rjmp debugPrintOneChar
+  sbr r17, (1<<TXC1)
+  sts UCSR1A, r17
+  sts UDR1, r16
+  sec
+  ret
+; @end
+
+
+
+