6502 QR Code Generator - (C)2021 Thomas Jentzsch

Instructions:

1. Include QRCodeGen.inc into the code area of your own code

2. Define the following constants:
   - QR_VERSION     = 1..3  ; QR code size (21, 25, 29)
   - QR_LEVEL       = 0..3  ; error correction levels L, M, Q, H
   - QR_SINGLE_MASK = 0|1   ; use only the 1st of the 8 mask pattern
   - QR_PADDING     = 0|1   ; add padding bytes add the end of test message text
   - QR_GENERATE    = 0|1   ; generate Reed-Solomon ECC generator polynomial on-the-fly
                            ;   else use built-in table

3. Define memory for code generation and displayed bitmap:
   - qrTmpVars      ds 9
   - qrData         ds QR_TOTAL
   - qrPattern      ds 1
   - qrGenerator    ds QR_DEGREE (only required if QR_GENERATE = 1)
   - bitmap         depends on platform

4. Implement two subroutines:
   - GetPixel: checks the pixel at position x (Y), y (X), returns Z = 1 if not set
   - InvertPixel: inverts the pixel at position x (Y), y (X)
   Note: Both routines MUST NOT change X and Y registers!

5. Add message text using macros
   - first START_MSG
   - then for each byte ADD_MSG_BYTE
   - finally STOP_MSG

6. Set qrPattern to 0..7 (chosing a mask pattern)

7. Use the GEN_QR_CODE and QR_CODE_DATA macros

8. Draw the generated QR code bitmap

That's all! :)