The 9 volt battery holder sucks :< I’m now using tape to hold it in place since it’s not possible to change batteries (how did I use all that juice!) when it’s affixed. Well, unless you take midiboy apart.
I really like how the Kastle (from bastl) synth solved the battery compartment problem. But thats a 3+ volt solution.
Aside from that, audio out plug 
I’ve hacked one on:)
Hey! Could you share a picture or more details on your audio out modification?
We tried many battery holder solutions, given all the design constraints of the form factor of the device, 5V being required for steady operation, parts count and the cost of the design, we arrived at the 9V battery holder on a separate PCB, but we’ll keep our mind open if it can be improved.
Oh, it’s a nasty hack But after initially wanting to mount a jack, I decided to put a pin header on since I’m testing with bread board.
And a short video in action at: https://poetaster.de/media/midiboy.mp4
I have a bunch of 4 piece AAA holders that I use in Altoid tin builds. They would ‘about’ work, but that would not solve the problem. I also have some 9 volt enclosures designed to slide out. That’d work, but they cost double, and I can’t even source one at the moment. hmmm.
Hi there. Another version 2 suggestion would be to make the design expandable/modular. Something like adding an i/o pin header for attaching rotary encoders and keys (custom) breakout boards. Which then can be fixed to the either sides & the bottom of main board. I guess following something like this could be done.
All the very best.
I’ve built a more general purpose 328p based solution (without display) at https://github.com/poetaster/rampart
It’s kind of agnostic but for signal processing rather than midi.
But for the midiboy, I’m still working on what I purchased it for. midi arps.
is the source of my inspiration. The arpi is a nice piece of kit, but too much for my needs.
I’m always a bit confounded about whether to add more or just see the device for what it is.
This week I finished to build my midiboy. A nice little peace of hardware.
For an improved layout, it would be nice to have some I/O-pins available on a header.
Currently all analog inputs of the 328P are used by the buttons. Some pins for this inputs would be handy, if I want to use potentiometers instead of the buttons, e.g. use only A- and B- button and 4 pots as controllers instead of the up-/down/left-/right-quartet or replace some buttons by a rotary encoder.
Same for the speaker ouput. If I don’t use the speaker, this would give 2 programmable I/O pins. May be together with the SPI-signals this can be used as an SPI-expansion with 2 independent CS-pins, for external ADCs, DACs, shift registers, multiplexers etc.
Roman
hey good day! did you ever get that midi arpeggiator working!?
No, I’ve been too busy with my own kit. I also got hung up on how much fun the simple note mutliplier (in the demo apps on the patch pages for midiboy) is:
But distracting as you know what.
I’ll report as soon as I find some time.
awesome… sounds kind of neat. I bought a reface cs and wish it had some arp function, and im trying to seek out a simple function. seems most devices are overkill for that function
