Hey, I’m super new to DIY synths, but I ordered a couple Fart Box pcbs in an attempt to make Christmas gifts. I see the board has inputs for cv1, cv2, and gate. Is there a relatively simple way to add a usb midi to cv conversion circuit with an arduino and wire it to the existing cv and gate? Usb is much more convenient for the friends I’m building these for and I’d like build to just have power, line out, and a usb port on the back. Any help would be greatly appreciated.
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A standard 5pin midi in would be ok too, but ideally I could do USB instead
Hi there, welcome!
Yes, it is possible. There are many ways to use an arduino to make a USB MIDI to CV and Gate. This is usually done by using an external DAC (Digital to Analogue Converter). Work out how many CV and gate you need and then choose a project from the many midi to cv examples on instructables (for example)
The Teensy 2.0 board may be the best place to start.
Do keep us posted.
An Arduino pro micro (based on an ATmega32U4 like the Leonardo) can be programmed to appear as a MIDI device over USB. I use one in my homebrew Eurorack MIDI interface, based on the original by Larry McGovern. It’s pretty easy to have both USB and 5-pin DIN MIDI, though you can’t use both at the same time. I think this original project just used DIN MIDI, but you can use the USB-MIDI library on a pro micro instead of the ‘normal’ MIDI library.
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You guys rock! thanks so much. I’ll research and get to work while my pcbs ship (5-20 days). I’m excited!
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Mcp4822 spi DAC has two outputs and plenty of Arduino support, or mcp4922 i2c DAC also has two outputs to control CV. What is the voltage range required for the fartbox as a DAC will only supply 0-5v without extra opamp multiplier and a higher voltage like +12v.
Also you could use PWM outputs from the Arduino to generate simple CV voltages without a DAC and just use an opamp to smooth and buffer the outputs, you can also level convert before or after the opamp buffer.
Also what are you going to send over midi to control the fartbox, I presume you need to generate a gate and two control voltages, CC messages are obviously ideal for the control voltages and maybe a note on/off to generate the gate.
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