Velocity implementation in MIOS

[SounDuke]

When I began to work out my first MB64, I was surprised for the lack of the velocity implementation in MIOS. TK answered me that no code was written because if velocity is what you need, then the best solution in financial terms is to mod a casio and midi merge it through MB. Lately I have found a 8x8 button matrix cannibalized from a casio and I found out about the extraordinary possibilities which are now opened to build a full fledged controller in conjunction with all TK's efforts in developing SM driver. I need several 61 keys controllers, and the high cost/poor midi implementation of commercial ones is incredible. First of all, it is impossible to find master keyboards with split zones (with MB you can assign every key to send the event you desire! So 61 keys means 61 split zones :D). I'd like to know if someone is going to work about velocity implementation, I could lend an hand (not enough experience to work it by myself). Thanks for the attention

[TK.]

Hi,

I guess that you need at least a keyboard matrix with double pole switches at the hardware side, and n delay counters (n = number of keys) at the software side. This should allow to measure the time which passed when you started to press a key (upper contact gets deactivated), and reached the bottom of the key (lower contact gets activated)

The main reason why you cannot find an application which supports velocity is just, that I don't own such a keyboard which I could use for experiments

Best Regards, Thorsten.

[SounDuke]

As stated in the midi controller topic in design concepts, the required hardware to accomplish velocity sensing in most of economics keyboards is the use of a rubber membrane, the same used in computer keyboards. I managed to find a complete diode matrix from a roland e35 equipped with 61 keys, with the relative sets of rubber switches which (I suppose) work like a potentiometer due to conductive properties of the rubber. Is it useable to achieve velocity?

[TK.]

How are these rubber switches normaly adapted to a keyboard controller? I've no idea how the hardware looks like, do you have a schematic?

Best Regards, Thorsten.

[SounDuke]

Sure as soon as I can I'll draw a schematic. In the meantime, I'll try to explain how it works. The rubber switches (each set is a 11 switches rubber stripe) are positioned under the standard plastic keys (the black and the white ones :D) in little holes carved in a plastic structure. Each rubber switch stands over a contact on the printed circuit, which is screwed very near to the plastic structure with the holes, and connects the lines to the row. when a key is depressed, the rubber switch activates the contact, the current flowing through the contact changes depending on how much the rubber is compressed, so that the switch works as a variable resistance. However, it will be clearer as soon as I find the time to draw schematics. Thanks for the interest Thorsten, I'll post photos too