2 replies to this topic

[Per]

Hello
Can anyone tell me how to find the checksum (the byte before F7) in FmBox voice/drum or ensemble files?
Is it 7bit or 8bit notation, and from where to where will i have to count?
Regards Per

[TK.]

Hi Per,

the checksum is calculated over the data part only (256 bytes)

Calculation (pseudo code):

    // data block is located in data[] array
    // create sysex string:

    Array<uint8> sysEx;

    sysEx.add(0xf0);
    sysEx.add(0x00);
    sysEx.add(0x00);
    sysEx.add(0x7e);
    sysEx.add(0x49);
    sysEx.add(deviceNumber);
    sysEx.add(0x02);
    sysEx.add(type);
    sysEx.add(bank);
    sysEx.add(patch);

    uint8 checksum = 0x00;
    for(int i=0; i<256; ++i) {
        uint8 b = data[i];
        sysEx.add(b);
        checksum += b;
    }

    sysEx.add(-(int)checksum & 0x7f); // 7bit !!!
    sysEx.add(0xf7);

Best Regards, Thorsten.

[Per]

Thank you Thorsten it was just what i needed
and thanks for the Fm Synth its a fantastic piece of work, and what a sound
Best regards Per