In our previous coverage of the build, the synth was monophonic, and the MIDI implementation was pretty shaky. After realizing the hard work was done, [Mich] re-wrote the MIDI interpretation module to keep 8 voices in memory. Now the synth can play 16th note arpeggios at 999bpm.
The original build used 8 pins to output the audio with an R/2R ladder for a digital to analog converter. This didn’t work well with a polyphonic synth (everything was clipped or noisy), so [Mich] moved to PWM output.
[Mich] plans on building a PCB for the PWM mixer circuit and adding the ability to receive velocity data from the sequencer. He’s also thinking about adding a sampler to the build, but isn’t quite sure about the best way to implement that. If you have an idea for [Mich], leave it for him in the comments. Check out the video below for a demo of the FPGA synth playing Popcorn.