[SUGGESTION] Replace eor #$0f line with two nop instructions for buttons with pulldowns to keep addressing unchaged

[pawelsky]

Hi, thanks for this project, it makes loading programs to the 6502 so much easier!

For those who have the buttons with pulldowns by default I'd suggest to replace the eor #$0f line with two nop instructions rather than commenting it out. That way it will not mess up the addresses of the library functions.

Here are the proposed changes in the bootloader.asm file

555,557c555,557
<     eor #$0f                                    ; deactivate / comment this line, if your keyboard
<                                                 ; is built with buttons tied normal low, when
<                                                 ; pushed turning high (in contrast to Ben's schematics)
---
>     eor #$0f                                    ; deactivate / comment this line, and activate / uncomment two lines below if your keyboard
> ;   nop                                         ; is built with buttons tied normal low, when
> ;   nop                                         ; pushed turning high (in contrast to Ben's schematics)

and in the Readme.md file

53c53
< 2. Should your keyboard not be built according to the schematics (so the buttons are normally tied _low_ and when pressed turn _high_), then you need to adjust the routine `VIA__read_keyboard_input`. Simply comment out line 555 in `bootloader.asm`. This will disable the XOR of the read value with 0xf. This way the keystrokes will be interpreted correctly.
---
> 2. Should your keyboard not be built according to the schematics (so the buttons are normally tied _low_ and when pressed turn _high_), then you need to adjust the routine `VIA__read_keyboard_input`. Simply comment out line 555 in `bootloader.asm` and uncomment lines 556 and 557. This will disable the XOR of the read value with 0xf and replace it with two NOP instructions. This way the keystrokes will be interpreted correctly and the addresses of library functions will remain unchanged.