Several months ago I asked you guys to help on a DX7's sysex formatting. The help I received was incredible.
Now I'm here again, with another sysex midi implementation question. I've got this old Roland MC-303 whose sysex I'd love to fiddle with. After perusing the manual, it seems that there are sound parameters you can control via sysex that aren't accessible on the interface.
The problem: I've never worked with checksums before.
The DX7 sysex messages were shorter (like 7 bytes or something). The sysex messages on The Roland are typically longer, including the checksum, for instance:
| F0 41 10 00 03 12 | 00 40 18 02 | 07 | 1F | F7 |
Header | Address | Data | Chksum | End
In the sxformat example in max, the example message seems to be for a DX7. The checksum on the MC-303 adds the address and data together, and subtracts it from 80(hex). How do you write a function that calculates this kind of message?
In short, I just wanna be able to fiddle with sysex parameters through max via a midi controller.
My apologies if this has been answered elsewhere; I was unable to find anything particularly specific to this question.