A typical complete example of a QR bill generation can be found here:
Typical example of a QR bill generation
Building the QrInvoice object.
QR Invoice without amount
Structured vs. Combined Addresses
Bill Information (e.g. Swico S1)
Creating output: Strings, QR images, PDF payment parts and receipts.
Payment Part & Receipt
Swiss QR Code
Swiss Payments Code
Parse output into data objects: Strings, QR images.
Validate strings and objects.
IBAN String Formatting
QR Reference Checksum calculation