How to configure QR coder encoder (Lior Saphira)

I need to create a QR code of my binary data, I've tried Saphira's solution, but the code example creates a QR code with Low error correction, for a string and I don't know for how many characters.

I would know how to configure these parameters:

- Data type to encode/decode (ASCII, binary) - Error Correction (M, L, H, Q) - Size of QR code (Small, large, medium)

I need also to know how many data I can code/decode according to the size and error correction used.

I guess I need to modify Zxing java code, but I don't know which code and I don't know how to be able to use these modification (I don't know Java world...)

Thanks a lot