A while back I received a lot of helpful guidance from KermMartian when I asked him about my idea for this project. It's not complete so far but I'm really happy with the progress of all of this.
I wanted to be able to control my DAW with my calculator because I felt like I could genuinely create a replacement for an expensive drum pad. You can see my progress here:



The main calculator part ends at the 1 minute mark so you can skip the rest if you're uninterested in my clock MIDI device.

So far it's worked out really well with very unnoticeable latency but there are still flaws because I'm really new to coding in z80 and such:
1. I cannot simultaneously press multiple buttons at the same time, which is a necessity in all drum pads. This is really important but I'm not sure where to go with my current knowledge of z80. If you think you can help me answer some questions, please post a response here

The rest of these issues are pretty menial:
2. The battery runs out quickly whenever I have this on for a while. I intend on fixing this by modifying the back of it so the calculator can take power straight from my computer rather than depending on batteries.

3. The device doesn't send an "off" signal when we've released the button that we've pressed. This is kind of important for a drum pad, but not a necessity for my purposes.

Once I solve this first issue I have with z80 I'll try to finalize this project and give an update on a more polished version of all of this with code and maybe some instructions on how to set up loopbe1/hairless midi/ableton.

Resources Used
ArTICL
loopbe1
hairless midi
and Ableton Live 9. You can use a free trial of it or any other DAW that accepts MIDI input

That's pretty cool. Nice work

As far as the battery situation goes, you might want to look at these.

This is a great idea! Thank you for the suggestion.

Very neat! What exactly does the clock do?

Nice! (Or should I say, NAS!) Multiple keypresses is definitely doable with addition direct key port reads.

Looks (and sounds) great! So is the calculator producing the MIDI signals, and the arduino just being used as a serial <-> usb device, or are you sending a special format to the arduino, which then turns it into proper midi? Also, what language on the calculator did you use? You mention ArTICL, which is generally for BASIC, but earlier talk about your "knowledge of z80", indicating you are using z80 assembly.

utz, the clock is attached to two potentiometers in the back that go to the second hand gear and the minute hand gear. I had to measure each potentiometer to see where it crosses the tick marks on the clock so if I passed each mark with the second hand moving clockwise from 12 to 5, I would trigger a midi note. The minute hand on the clock is just to change the type of values that I would trigger with the second hand.

Ivoah, the calculator just used BASIC right now because as you said ArTICL is generally for it. However, I'd really like to learn how to use z80 in conjunction with ArTICL or maybe see some example code using it because of the first issue I'm having with this project. Also, the calculator sends the values of the keys that are pressed and then I use the arduino to convert that into midi messages that are sent through the serial port and interpreted by hairless midi.