Adding a 49 keyboards directly to the Shruthi (no midi) by chaining 74LS165?

Hi every one !

I was wondering if it could be possible (I mean , if my Shruthi could handle this… ) to add a 49 notes keyboard directly connected to some 74LS165 chained with the one used by the 4 switches. In fact, I would like to add a keyboard to my Shruthi but not via midi !
Software has to be updated but does it sounds feasible ? (in term of microprocessor timing etc etc).
If not, does removing some functionalities like the sequencer for example could improve the speed and the overall calculation ?

What do you think ?

If you play very slowly…

As Frank said, the 74hc165 is scanned rarely (I think the refresh rate is way slower than 100 Hz) - which is enough for reading panel switches but not enough for scanning a keyboard and accurately reproduce your virtuoso timing.

What eats CPU time is the sound synthesis itself, the sequencer takes at most 1% of the CPU and 0% when not in use.

The best option is to use a cheap MCU (Picaxe, ATTiny) and run a simple MIDI merger + keyboard scanner on it.

Or just get any 49€ masterkeyboard…

The thing is , I don’t want to have to set midi channel on the keyboard side AND in the Shruthi …
Using a merger would imply that the Shruthi is in midi omni mode “on” …
May be redesigning the “switch interface” (mix interface switch and keyboard switch - like it is on 80s synth like the prophet 5) and having a higher refresh rate ?

I don’t see why using a midi merger would imply that the shruthi should be in Omni mode…
What is the problem your are trying to solve here? What exactly do you need from your shruthi?

I think his problem is that whenever he will change the MIDI channel on the Shruthi, the MIDI keyboard will have to be reconfigured so that it sends notes on the same channel.

Much much work to avoid setting a MIDI channel from time to time…

The “problem” I would like to solve is exactly the one describes by Olivier. My main target would be a “all-in-one” shruthi (ala synth project) without the need to configure midi.
May be the key would be to move up to a more powerful CPU like the SMT32 series … but I don’t think I’m ready, have enough knowledge, to do the step.

But why would you constantly change the midi channel used by the keyboard attached to the shruthi? It doesn’t make any sense to me… Why not set the keyboard+shruthi to something like channel 15, and leave it there?

yep, I think exactly like V’cent.
Plus, if you have a keyboard permanently assigned to one shruthi and you don’t plan to use incoming midi messages, you can just leave it ‘permanently’ on any channel. You know that you can save the boot midi channel in the setup of the shruthi right?

K. Let’s take an example. When you buy a “Mopho keyboard” from DSI, you don’t set the keyboard midi channel and the "synthesis part " midi channel ? You expect to change channel in one place right ?
May be, what I should have mention is that I wanted to build a “all-in-one” shruthi with dedicated potentiometer, keyboard, pitch bend wheel, mod wheel etc …

Personally i have on all Keyboards Local Off and different Send and Receive Channels as i route everything MIDI (and CV :wink: ) thru the Device with the big C in the Name…

Doepfer MKE

I don’t understand why it is so painful to change MIDI channel. It only takes a second.

but with a merger inside, can’t you just assign 2 input channels and simply route them both to the same output channel?

BTW, I’m curious how many daisy-chained ICs like 74HC165 & 74HC595 can be connected to the same AVR’s pin (a “clock” pin) and not get it damaged?

depends an your power supply…

Why would they damage the AVR pin?

Because of excessive current draw…?
I need to make something like this:

According to the datasheet, the 165 inputs take only a few µA. So you’ll need A WHOLE LOT to reach the 20mA per pin or so you can do with an ATMega.