Pio

A guitar with active pickups will have the buffer is already built in. Otherwise, i'd recommend a HiZ buffer. Plenty projects are available online. I've made a simple stereo buffer project which can be soldered on a perf board...

If this means that you are connecting the jack on the AudioAdaptorBoard to an external device, like an amplifier or an audio interface, then it might be the problem. This Jack is a headphone output, referenced to a virtual ground (which is not...

It is not that bad as it sounds. Understanding what the capacitor does and which parameters are critical allows to use the X7Rs without problems. They work in millions of devices. To test, i've picked up two 0603 caps made by muRata, both...

Schematic: got last small changes: in the gain setting area I've moved the digital pot to the feedback loop of the opamp. This way the gain control will be linear with the correct range. Switched all decoupling caps to 0603 1uF to minimize the...

One small thing: according to the simulation the max gain needed when the Expression Pedal pot is 10k is 11x. Right now U1 provides the 11x gain when the digital pot is fully shorted (1+(R4/R5)). In practice the digital pot will have some series...

Latest schematic:

Looks like it's the same part, different manufacturer. Should work fine.

This way: It's a fun project, close to what i have been doing for the last ~30 years. Happy to help or just throw ideas in. Hope you will document it with nice pictures! :)

The built in zener diode is rated for 5V, with 3.3V it will work below the reverse breakdown voltage, maybe pulling a tiny current only. The two pairs of clamping diodes (instead of 2xBAT54S) will work. I'm trying to use parts available at LCSC...

There are dual footswitches with stereo TRS jack output, like the Hotone Ampero FS-1 Making one is also trivial. The dual jack ones would have to use an 2xTS -> TRS adapter. With the TRctrl signal low: Plugging a dual footswitch using a TRS...

D1 clamps the voltage coming into the opamp. For the ring, you are right, RC filter does provide some protection for the Teensy GPIO, combining R9 + Teensy's internal clamping diodes. I think, since there are two signals, i could throw an USB ESD...

A few points about the PCB design: Layers and stack up. This is a simple circuit, it is possible to route it on 2 layers only. Using 4 layers and with unconventional stack up - no dedicated ground plane, but the whole bottom layer is 3.3V...

Another option could be a HW Timer + Input Capture, which often already have glitch filters built in. Chapter 56 in the https://www.pjrc.com/teensy/IMXRT1060RM_rev3_annotations.pdf The quadrature decoder logic can be bypassed (bit 9 in the CTRL...

Is the "PEDAL" connector keyed, like the JST ones? Or just a pin header? Having the Vcc and GND as 1st and last pin will create short of someone accidentally plugs the cable backwards. Putting GND right after VCC will be safer. I can take a look...

Bottom row of 10k resistors + MCP4018 needs power. Add VCC to the left side of C4. C4 should be placed close to the pin1 of U3.

Here is a new, updated with the suggestions version, KiCad8. I haven't touched the PCB or footprint associations. It's schematic only. I have used a simpler variant of this circuit in the 1st prototype of the TGX4 pedal. Using it on daily basis...

Looks good. Ring will be exposed to the outside world, i would add at least a simple RC protection (1k + 100n, same as R3+C2) plus an internal pull-up enabled. The ADC2 can be any logic input, not an ADC one. You can use ADC to sense digital...

Maybe it will provide some inspiration. In one of my projects i've used an adjustable power distribution switch (BL2555) + comparator to limit the inrush current while charging a 1000uF cap: https://github.com/hexeguitar/4WD_UART BL2555...

You can actually omit the R7 + R8 if minimizing the part count has a high priority. I tend to use an external pull up + one small series resistor for signals that connect to the outside world. Sure. it's not directly connected, the S -switch gets...

Opamp is powered from the same 3.3V as the Teensy. If the gain is too high the signal will be simply clipped at that level. The amp can't produce an output voltage that is higher than it's power rail. At least not in this application. In practice...

Mono jack will not work with this socket configuration. A mono jack has the Sleeve+Ring as one contact. The jack socket in the circuit above has the T+R shorted = all three contacts will be shorted to GND, no matter what the switch position is...

R+T tied together - this is what i have been trying to explain in the previous posts. Maybe this picture will explain it better. Let assume we have the Exp pedal jack configured as: T=signal/wiper, R=toe position/pot top setting, S=heel...

with the input connection as in the posted schematic, where R+T are tied together, there is no need to swap the polarity. The pot acts as a single variable resistor in both configurations. I would advice against it. It looks like the MCU used in...

I think i deleted it, wasn't anything spectacular. Just a "hey! it works" kind of riff ;)

explained in the comment directly above that function. What it takes as delay time parameter is not the time in ms, but scaled to 0.0-1.0 range value which is mapped to the max available delay length. It's just a design approach which i use in...

OK, so quite a bit later than advertised, but I've made some progress. Prior to doing a PR I want to sort out an example showing how to access the SD card while streaming audio from it, and update various bits of documentation, but the current...

Made this simulation: https://www.desmos.com/calculator/ycpupbbkec It shows another drawback of this solution: R1 + pot inside the Expression pedal create a voltage divider with the variable bottom resistor. This changes the taper of the pot...

Disconnect the MISO signal from the ADC and short it to GND. Does the SPI test return 0s instead of 0xFF? It will tell if the issue is with : - ADC chip, it's config, wiring etc if the SPI reads 0s. - Teensy SPI side or the library if the value...

Simplest way, which is safe and handles both plug polarities would be to use the pot as a rheostat: Downside is it requires calibration for the max range and depending on the pot resistance the range will be different.

Up and running on my multi synth sequencer, and sounds very lush. Not sure why the shimmer does not have much of a tail to it, but I've found that using reverb pitch shift gives me the shimmer effect I was after so not a dealbreaker :-) Many...

We have the amp module, powered from the power bank and with inputs shorted being silent. Noise is there if the R+GND are connected to the TeensyAudioBoard, am i correct? I2S is relatively high speed interface, MCLK clocks everything inside the...

Ok, if the module, with it's inputs tied to GND still produces the noise, it is either: a bad board or dirty 5V supply rail. More tests: Disconnect the 5V line from the Teensy and try to power it from another source (powerbank maybe?) Teensy +...

If you disconnect the input signal and short both L and R inputs on the PAM8403 module to GND, is the noise still there? If yes, the source is the amp and most likely the 5V power bus. The output signal from the Audio board should be the Line OUT...

Transdimensional is a fancy name for a way to simplify the use of very complicated synthesis algorithm. It is a kind of morphing that takes care of navigating through the synthesis parameter hyperspace. This first synth navigates in a 54...

https://docs.arduino.cc/software/ide-v1/tutorials/installing-libraries/ Scroll down to the Manual Installation section and follow the steps. Works with the IDE v2, too: