slider synth

Created by [@Danny] • Started on July 23, 2025

A esp32 based synth that uses a touch pot and fsr.

Total time take: 15 hours

June 23rd: Planning + Schematic

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I used some of my own references as well as these ones below. I was able to setup a lot of essential features like usb c flashing, 5v to 3v3, uart, and boot/reset buttons. * devkit schematics * esp32-s3-wroom datasheet * user guide

Total time spent: ~4 hours

June 24th: Adding more features

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I finished all of the audio circuit above and added more features like led indicators and a rotary encoder for extra control.

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Total time spent: ~6 hours

June 25th: Placement, Routing, CAD, and everything else

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For placement, I had a solid plan of selecting an entire box/feature in my schematic and seperating that to then place.

After everything was placed, I can finally route and rotate any components if needed for better routing.

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I made a simple case that would press fit onto my plywood strip and pcb. I wanted it to be flush with the thickness of the plywood to not add any extra height.

Total time spent: ~5 hours

MILESTONE: MY PROJECT WAS APPROVED!!!!

Time to wait for the grant and everything to be shipped.

Total time spent: ~0 hours

August 4th: PCB Assembly

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My pcbs arrived! I chose to not to include some parts as it would cost more to assemble. I have some on hand already, like the esp32-s3-wroom.

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I also did not order a stencil, so I had to manually apply and shape the solder paste to each pad. It was okay.

Total time spent: ~4 hours

August 5th: Finished Assembly, now Debugging

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I am so glad I connected my UART to these headers for debugging on my oscilliscope. For some reason, I can't get platformio to read any serial.

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I am so stupid. I did not check if the pinout i chose for my force sensitive resistor supported adc. (IO38) I had to solder a jumper wire to fix this issue.

Moving onto the code part, something is not right. I am using mozzi which is a dsp library for synths. For some reason, it either outputs nothing or strange frequencies. Hopefully its not my schematic that is wrong.

Total time spent: ~6 hours

August 6th: Finished!!!

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I found out the original reason why my synth sounded strange. It was because i was calculating my hz wrong for my scale, as the numbers were very large/wrong.

I put four leds and a encoder with a button to cycle through modes that modify the synth's sound.

After making sure everything was programmed right with little bugs left, it sounded neat and has tons of possibilities now.

Total time spent: ~4 hours