#e-drum

Attach ordinary header pins to the shield.

Use it like a photo. Please note that if you put the shield down, you can not use it with breadboard.

This time, only piezo is connected.

Details are written on the following page, but using this audio shield will reduce the number of pins that can be used with Teensy. https://www.pjrc.com/store/teensy3_audio.html

As you can see from the above figure, pins 14 to 23 are analog pins, but if you use a shield, 14, 15, 18, 19, 22, 23 cannot be used.

The available analog pins are 16,17,20,21. If many piezos are connected, a multiplexer is required.

Teensy can be developed using arduinoIDE by using software called Teensyduino. Installation is easy if you follow the official procedure.

※For Mac, Catalina still seems to be in beta.

Teensyduino - Add-on for Arduino IDE to use Teensy USB development board

First, watch this video because Audio features are too rich.

It’s long, but you can see most of the features.

As mentioned in the tutorial video above, Teensy provides a special tool called the Audio System Design Tool. Build an audio environment with visual programming.

This time, the audio environment was constructed as shown below.

The “playSdWav” on the left is the Wav player. The reason why there are as many as 16 is that the number of sounds played simultaneously is the same as the number of playSdWav. For example, if you want to make the next sound while playing the previous sound when hitting repeatedly, if there is only one playSdWav, the previous sound will be stopped and the next sound will be played. That’s why it may be a bit more for the time being, but I’m preparing 16 for the time being. The mixer in the middle is a mixer as the name suggests. Each mixer has 4 channels, so you need 10 units to connect all as shown in the figure. “I2s” on the right is the audio output on the shield.

The sgtl5000 below is the chip on the shield. Although it is not connected to anything in the figure, it is necessary as a magic to use a shield.

You can build an audio environment like this by connecting patches. These can be exported as code.

I wrote a code that senses the piezo and changes the sound source according to the velocity. As always, I use my own library for piezo sensing.

https://gist.github.com/RyoKosaka/1399dd99065e2668f99befba74239ed2

playSdWav can determine whether it is playing with isPlaying (), so if there is a response to piezo, the sound source is played with playSdWav where inPlaying () is false.

Here is the video.

It corresponds to velocity. The reaction speed is very fast, but the choice of the sound source was not good or the dynamics could not be expressed much. Well, I only used only 5 wav files.

Regarding the sound source used, there is an open source VST plug-in called DrumGizmo, and I used a sound source called DRS Kit by DRS Drums released there. License is CC BY 4.0. Thank you.

Here are the wav files I used.

It works fine in the video, but sometimes it becomes unusable because it sometimes becomes unresponsive or crashes with the worst sound. It is easy to crash if you hit repeatedly. The cause is unknown at the moment … Is it possible to solve it with Teensy4.0?

What’s different is the resistor and the diode. In the past, only one resistance of 1 MΩ was connected to one piezo. Like this.

However, I connected this same circuit to the 74HC4051, and when I hit 1 piezo it all reacted and it was useless. Recalling that MegaDrum used the 74HC4051, I tried the circuit and found it somewhat better.

MegaDrum is MIDI trigger module has been under development since 2007. The main IC is ATmega 324 p. You can download the schematics and firmware and create a parts list, but the firmware source code is not available. You can just make your own. But the schematics are helpful. According to a Vdrum forum thread, MegaDrum’s input analog circuitry is very similar to Roland’s TD-10.

Now, the code. There is nothing particularly difficult. The Sparkfun tutorial is easy to follow. If you just want to read the value, you can use the following code. It just switches with the for statement.

https://gist.github.com/RyoKosaka/cac5935d894f208e4c32fe6a13e8e573

Now you can read the eight piezo values.

I could read the value, so I could sense it using my old code and send a MIDI signal. But I want to use my own library for the sensing part.

So I made my library compatible with ESP32 and analog multiplexers. But I need to adjust the codes and circuits more.

Here’s a video of a test using the library.

First of all, initial setup is necessary to use ESP32. It is explained in detail on this site. please refer.

https://randomnerdtutorials.com/installing-the-esp32-board-in-arduino-ide-windows-instructions/

Refer to the figure below for the circuit. Since it can also feed from USB, the battery box is not necessarily required.

Remove the battery box when writing the code.

Next is the code. This thread is helpful.

https://github.com/nkolban/esp32-snippets/issues/510

I merged the code at the beginning of this thread with the piezo sensing code I made earlier.

https://gist.github.com/RyoKosaka/1f488427e02054422966fb9625c9f8e5

Unfortunately neither arudino midi library nor hellodrum library is currently available for BLE MIDI.

I plan to make the hellodrum library correspond to ESP32 either.

Finally, connect ESP32 and PC.

Is this your first time using BLE MIDI? Do not worry. KORG makes a very easy-to-understand manual in multiple languages.

https://www.korg.com/us/support/download/product/1/305/

How is it? I was surprised at the low latency. BLE MIDI is very useful.

It's a brilliant solution. I have not tried the easiest way to make it with flexible filaments.

You can purchase ninjaFlex from the adafruit.

https://www.adafruit.com/product/1690

Unfortunately, in Japan, it was sold at a very expensive price, so I bought a TPU filament.

https://www.sainsmart.com/products/all-colors-tpu-flexible-filament-1-75mm-0-8kg-1-76lb

It is very soft. I can bind it.

I measured the dimensions of the trigger cone and modeled it and printed it with TPU.

The setting of infill is 20%, 10%, 0%.

At 20%, the cone was too hard. At 0%, the cone was too soft.

The center of cone is just good hardness, but the wall of cone is conical so it is strong against the force from the top.

Clearly the feel was different from sponge form, but when we tested it by connecting to Roland's TD-10 it was able to be used without problem.

Unfortunately, with the library I wrote, it could not sense the vibration of piezo better than sponge form. It seems that the power is too strong and the noise of the signal is too much.

By improving the shape of the cone, it may be possible to sense well. I will try it.

By the way he also uploaded the mount parts for roland.

https://www.thingiverse.com/thing:2924429

I just designed it and I have not printed it yet. I will try to print in my spare time.

These images are rendered images of Fusion 360.

The model data is here.

https://www.thingiverse.com/thing:2644566

And I also updated the mount parts so that it can be used for these models.