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Raspberry Pi & MCP4922 Based Sequencer

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I have combined the 555 Oscillator with a sequencer. The RPi outputs a value between 0 and 1023 over SPI to the MCP4922, a DAC which creates a voltage in the range 0-5v. The code is designed to conver a MIDI not number from 0 - 127 to the value output over SPI, so this is effectively 1 volt per octave (obviously there is no MIDI yet, but this is in preparation for what is to come). The As mentioned, the oscillator has a CV input. However, it does not respond to 1v/oct, so it is not at all musical. It is actually inverse and linear, so it is more akin to the Korg standard, but is not calibrated to that either so would still sound terrible with an Korg sequencer. Here is the schematic: Here is the link to the 555 Oscillator Here is the source code on Github. Here it is in action:
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Simple 555 Based Oscillator

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I'm just starting out, so I wanted to build the simplest CV controlable oscillator. Here is the schematic: I could go into the details of the workings of the 555, but that has been covered in depth elsewhere on the internet. You can hear the results in the next post when it is combined with the sequencer>
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