jtadams

Hi all! In further analyzing the ability to MIDIfy an old Allen MOS-1 console in-place, i.e. without dismantling the existing electronics, I realized it is using some form of keyboard diode switch matrix. Hence the following questions. I apologize if this is already documented somewhere, but I did look around and did not find any answers. I'm somewhat familiar with electronics and with the design of the DIN module, but not with the details of the Allen design nor with MIOS or MIDIO128. 1. Can I assume that the existing electronics are polling the matrix and that I can determine whether a key is pressed by performing a logical XOR against the two inputs representing the two switch contacts? (If a key is pressed at any given moment in time, thus closing the switch, then both voltages must be high, or both must be low, at least if I'm understanding correctly.) 2. I understand that MIOS can poll a DIN module once each millisecond . . . won't the probability of the existing organ's scan rate being much higher make this too slow? (I assume it is a supersonic frequency, so as to avoid interfering with the actual signal, and if so then the state of these pins will change many times within that millisecond.) 3. Is there any functionality already in MIOS and/or MIDIO128 that I'm somehow missing that would allow me to interact with the keyboard matrix? 4. Is there an easy way to scan the matrix if the organ is turned off, without any risk of damaging the existing electronics? (I wouldn't think so since we'd have to apply some voltage to one side of the diode array in order to read the outputs and I have no idea what effect that would have on the organ's electronics, but again maybe I'm missing something.) Thanks!

Thank you for your reply! I hope to be able to use MIDIO128, perhaps with similar modifications so as to accommodate the 7-8 DIN modules. I'm not quite ready to write my own app yet but I can probably figure out the necessary modifications to MIOS and MIDIO128 as long as there's some reason to think that - with the STM32 based core - it is likely to work and not run into timing or other similar issues. Thanks again!

Given how much faster the new STM32 core should be, compared to the old PIC based cores, is it now potentially feasible to support more than 4 DIN modules using the same core? If so, would any modifications to MIOS be required? (Most likely I need 7 or 8 - this is for MIDIfication of a medium sized organ.) Thanks!