Basically, we are going to use 2 controls, instead of one. One control for the positive sliding, another for the negative.
Heres the example and work around incase it helps someone, if anyone can add any tips, please do, Im new to MD2.
The Sysex command for an E-mu Master Tuning Offset parameter (37h, 01h) is as follows :-
F0 18 21 00 55 01 02 37 01 00 00 ** F7
The * is a standard Roland checksum (you can use F7h to ignore checksum), the green is the parameter ID (Tuning Offset), the blue is the data needed to change the tuning. (LSB first)
A data value of 01 00 sent to the sampler changes the Tuning offset from 0 up to 1, a value of 02 00 changes it to 2 etc etc simple enough.
But if I want to change it to -1 (negative) I have to send a data packet of 7F 7F (2s complement). If I want to change it to -2, its 7E 7F, -3 is 7D 7F etc etc
So to do this we can use two dial controls. Set them both to send Sysex and load the commands. One control should be named Positive, the other Negative. One control will slide from 0 through to 24 the other will slide from -1 to -24
We simply set the fist controls sysex V (value) to one byte, enter V 00 for the data packet (as its always 2 bytes for E-mu, you could set the V (value) to 2 bytes, but, for this example, I'll leave it as 1 because when we do the negative control we will be forced to use only one V byte). Set the controls Midi Min Max to 0 - 23, set up a Named Ticks for pretty UI if needed and it will work fine.
For the Negative control, set it up the same (Copy Similar) but we are going to change a couple of values.
First, set the data portion of our Sysex to V 7F (2s complement) and set the Midi Min Max to 127 - 104 (this will output 7Fh to 68h) , recreate/number your UI (tick lists etc) and now turning the knob sends the E-mu 14 bit signed numbers and we can dial from -1 though to -24.
To the MD2 team, I love this app, its sooooo cooool!! Keep up the great work!