tomas

For what it is worth, I am developing Teensy code on PC in Visual studio. I don't need fancy simulator. From audio library I am only using DMA streaming code, nothing else, on PC side I am using ASIO to get pretty much the same low latency...

Apparently you did not notice what I wrote before. Teensy never sees voltage above 2.5V in real life at the analog input. I would need to get the assembly completely wrong to get anything above 2.5V. Typically you don't protect circuits against...

You might consider using multiplying DAC. Such DAC has digital input and analog input. The analog input is multiplied by the result od digital to analog conversion. If you drive analog input of such DAC from Teensy digital output you would be...

You might consider using multiplying DAC. Such DAC has digital input and analog input. The analog input is multiplied by the result od digital to analog conversion. If you drive analog input of such DAC from Teensy digital output you would be...

As I wrote: spec say max voltage on any pin Vdd + 0.5V. I am within specs even under most extreme situation (wrong assembly, reverse orientation of magnets, keys with wrong orientation pressed to max). Under normal operation I am always below...

Yes, the purpose of those transistors is to allow to implement power saving. Since there are lots of Hall sensors their total power consumption might be >300mA. The idea for those was to enter power-saving mode when keyboard is not used for...

That is interesting. I bought a couple from various "shops" on Ali and they all had BB logo, and they sounded good, but I am wondering what stops fake makers from putting BB logo? And how do those "fakes" behave? They don't work at all? Or sound...

@Lawrence - just my 2 cents worth, I would highly recommend I2S sigma-delta DAC like cheap PCM5102A (something like $3 on Ali) it sounds 100x better than PT8211.

Your project looks fantastic and I admire your productivity. Arriving to finished version in so little time is an achievement. I wish I could motivate myself to do more 🙂

Thank you all for comments. I am not very surprised that Hall sensors are sensitive to magnetic fields - that's what they are made for. I am also not surprised that speakers produce magnetic fields, that's their principle of operation. With that...

I would say 2x longer is minimum :) In the past when I was asked to provide quote for the project I always multiplied my ballpark estimate by 2 :)

There is one thing I have noticed that I think is the reason why Hall sensors aren't used in commercial musical keyboards design. As it turned out during experiments, Hall sensors are susceptible to electromagnetic field (no surprise here really...

Yes I thought I needed extra protection, but then I checked 4067 analog multiplexer data sheet. https://www.ti.com/lit/ds/symlink/cd4067b.pdf Every input is protected internally (see below) and since I am using Vdd=3.3V supply for the analog...

OK, my calculations above are off by factor of 4.7 because I have 1kΩ resistor in series after multiplexer so actual time constant is 63ns and time required to charge ADC capacitor would be 1.4µs , but this does not change the fact that with 62...

Thank you for showing so much interest in my project! It is really appreciated! To quickly answer some of your most important questions: 1. I am currently using neodymium magnets with diameter of 6 mm and thickness of 2 mm. No I did not...

@Pio I just wanted to say that this is one of the most amazing projects on this forum. Congratulations! I am watching your progress, since some years ago I did a prototype of guitar FX box using STM32F401 which is nowhere near to Teensy 4 in...

Yes I noticed that. I am now thinking why it is so, but on the other hand it doesn't bother me that much, as I am using threshold to detect pressed key and currently I have set note-on threshold at level 2000, so it is far far away from any...

Yesterday I wired the keyboard to the controller and found one tiny error in the printed circuit. After fixing it I wrote the program that simply reads the Hall sensor values from all 48 sensors using three channel ADC and analog multiplexers on...

This is such a cool project. I'm also in the business of refurbishing an old keyboard - in my case, giving a toy keyboard with rubber dome switches nicer-feeling mechanical switches. Still only on/off. However, I've realised using hall effect...

I'd say you've done some GREAT homework. Bravo! Now, get coding and let us know how it goes.

That is even better. With (1/distance^3) interference between keys is much lower. And with very close distance to one of the poles (when key is pressed and one pole of the magnet nearly touches the sensor), I got more of 1/distance^2...

I wasn't aware of organforum. Thanks for the pointer. Before I wrote first post, I already made experiments with few keys. I am using really small magnets that are specifically selected to minimize effects of magnet interference. Magnetic drag...

Thank you for showing interest ! This is appreciated. I hope to report some more progress this week.