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Testbild-synth / Hagiwo_009_030_sequencer

A through-hole PCB conversion of HAGIWO's 6 channel eurorack gate sequencer. Includes Gerbers, Code and building instructions.
MIT License
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Please move outputs 2,4,6 to PWM pins and add optional LPFs #4

Open BenignCremator opened 1 year ago

BenignCremator commented 1 year ago

What I would like to be able to do is write alternative code for this module that would group pairs of outputs (1 and 2, 3 with 4, 5 with 6) into gate and CV pairs, allowing the module to output three tonal channels instead of six atonal ones. For this, output 2, 4, and 6 need to be moved onto PWM pins. If I am reading the schematic correctly, outputs 2 and 6 are currently on PWM pins, and only D4 needs to be changed. One way to do this is by swapping D8 and D9, or moving outputs 4, 5, and 6 to D9, D10, and D11. Also, since this would require using PWM output to generate a CV signal, low pass filters would be a good idea on those pins. A simple resistor-capacitor filter should suffice, though adding an on-board op-amp for buffering would be a nice to have. Is this a do-able and reasonable? Please let me know and thanks in advance.

Testbild-synth commented 1 year ago

hi, first of all thank you for your interest in the module and willingness to contribute!

since I planned to do a redesign of this anyway I might as well do that. keep in mind that running the PWM loops with an I2C screen connection at the same time might get a bit iffy in terms of programming it (I have used SPI screens before and had quite a few problems with audio artifacts/noise being introduced.) If you want we can coordinate on this, I'd be happy to give you other contact details :)

My main constraint here is I wanna keep it to one PCB and fully through hole so I'll try to make it work

BenignCremator commented 1 year ago

First off, my apologies for the delay in replying. I got wrapped up in end-of-semester reports and finals. At any rate....

Keeping it one PCB and through hole is a good idea. Not certain if a TL074 with some additional passives will fit on the board as is, considering any op-amp will need the +/- 12v traces routed to it. I assume that this is a 2 layer board and moving to 3 or 4 layers is also off of the table. Another option is to use transistor buffers instead of op-amps, that may take up less room. And the goal is to output CV, not audio, so low pass filters should be able to take the noise from the I2C out of the outputs. The big concern there is the time for the CV signal to settle. There is some discussion about this out there. Hope this helps, and if it is not feasible, no worries. Will just build whatever the result is, already have components for it. Thanks in advance.

https://electronics.stackexchange.com/questions/354405/converting-pwm-to-analog-voltage https://forum.arduino.cc/t/arduino-pwm-to-cv-for-analogue-synth-using-max-msp/352602