About Ronna Technologies

Hi, I’m Jeremy, founder of Ronna Technologies.

Making an affordable drum module has been one of my main projects since 2017.
Although making drum modules is not the sole purpose of the company, it is what started it.
So I’ll take a moment to explain how the company came into existence
But before I go into that, I have to explain how a drum module is made.

What’s in a drum module?

Essentially, a drum module converts sensors output voltages into sounds.
For instance, a snare drum contains at least one piezoelectric sensor. When the drum head is hit, this piezoelectric sensor (piezo) converts vibration of the drum head into a voltage. This is the de definition of piezoelectricity: it converts a mechanical stress into an electric charge.

But there’s a catch: the resulting voltage is very high, and goes from negative to positive values.
This is why the first piece of a drum module: a piezo signal conditioner interface.

Piezoelectric signal conditioner

A piezoelectric signal conditioner is an electronic circuit that constrains a piezo’s output voltage to a given range of values.
Most microcontrollers operate from 0V to 3.3V, or 0V to 5V.

There are many ways to make a piezoelectric signal conditioner, but the first stage is always used to scale down the voltage and protect the rest to of the circuit.

The rest usually depends on specifications. Especially regarding the use of a symmetric power supply.
But even if a symmetric power supply is used, at some point the mapped voltage will have to be within the [0, 3.3]V range.

This is what the first product of Ronna Technologies does.
EveryDrum is a drum trigger signal conditioner interface.
The piezos that are connected to the board are connected to an analogue electronic circuit that maps their output voltage to the [0, 3.3]V range.

Analogue to digital converter

Once it’s been scaled to the desired range, the output voltage of a piezo is digitized and processed in order to produce a sound.

In order to digitize the piezo voltage, an Analogue to Digital Converter (ADC) must be used.
It can be an external ADC, or a microcontroller’s integrated ADC.
In both cases, this steps allows processing the signal using various digital signal processing (DSP) algorithms.

Usually, it’s best to get about 10 samples of the piezo’s voltage every millisecond.
That leaves about 0.1 ms between each sample, so the DSP algorithms must be fast enough to process a sample in less than 0.1 ms.

Digital signal processor

Once the piezo’s voltage has been digitized, it can be processed.
At this point, all the electronics is done, it is now a matter of software and DSP algorithms.

Usually, the waveform is processed in order to find a peak velocity.
Depending on which instrument has been hit, a note is chosen, and a volume associated to that note is computed from the velocity.

Sound generator

This last step is optional, if it is ignored we don’t really talk about a drum module any more, but rather a trigger module.
However, if this step is not ignored, things can become tricky.

The goal is to generate sounds from the previously computed notes.
What makes this step tricky is that everything must be done in a few milliseconds, at most.
This is where performance really matters.

Past projects

Before Ronna Techologies, I have worked on a complete drum module: eXaDrums.
It includes all four steps mentioned above, even the sound generator.

eXaDrums

Initially called RaspiDrums, eXaDrums was created in 2015.
My main goal was to make a modern drum module with a touchscreen user interface.

In 2016, eXaDrums was the first drum module offering a touchscreen interface.
It used a Raspberry Pi 3, which was not a very powerful device, but allowed a latency as low as 6ms.

More info about the project here: exadrums.com.

eXaDrumino Nano Every

This project is closely related to eXaDrums, as the name suggests.
It’s also my first real Arduino project.

The goal was to make a drum module using an Arduino Nano Every.
With the Arduino’s ATMega4809, an 8-bit microcontroller running at 16MHz, it was quite a bit of a challenge, but it did work out pretty well.
More info about the project here and here.

For this project to work, I had to make an electronic board that maps the piezos voltages to the [0, 3.3]V interval.
I also had to ditch the Arduino libraries completely and write the firmware in bare C++17, using AVR GCC.

You’ll notice that I have used three of the four ingredients that make a drum module.
To get the fourth ingredient (sound generation), the Arduino needs to be plugged to a PC.
But guess what, exadrums is compatible with this board!

So, at this point, I was confident I could make a complete drum module, including the electronics.
Furthermore, the exadrumino’s performance was very good, given the hardware that I used.
I thought selling the board would make a lot of people’s lives easier.
But the thing is, in France you can’t really do that without creating a company, so I decided to start my own company.

Current projects

To be honest, I didn’t want to start a company to sell a single product.
As stated above, a drum module is made of four parts, so maybe it’s not a bad idea to have a product for the first part.

EveryDrum

EveryDrum is a drum trigger signal conditioner interface. It’s based on the board that I made for exadrumino.
Actually, it’s just an analogue electronic board that maps piezos voltages to the [0, 3.3]V range.
It has two female headers that are compatible with the Arduino Nano Every.
You can use any microcontroller you want, as long as the pinout is compatible with the Arduino Nano Every.

There is also an additional input for a hi-hat controller.
I will share more information about this project in a future post.

Other projects

Of course, I’m working on other projects than EveryDrum.
Right now, there are two projects I’m working on.

The first one is a trigger to MIDI module.
So far, I think it will have at least 12 inputs: 9 triggers, 1 force-sensing resistor (FSR), and a few switches, perhaps 3 or 4 of them.
A bigger version of the board will have more inputs. Probably something like 15 triggers, 1 FSR, and a few switches.

Before we continue, here’s a quick reminder about e-drum sensors:

• Trigger: basically a piezo sensor that “triggers” an event every time its voltage reaches a certain threshold. Used in snare drums, toms, etc.
• FSR: force-sensing resistor. It converts a force into a resistance, which can be converted to a voltage. Used in effect pedals, such as hi-hat controllers.
• Switch: simply a switch. It is open by default, closed if pressure is applied to it. Used in cymbals to determine if they are to be choked.

The other project I’m working on is a development board.
The goal is to have something better than an Arduino Nano Every to use with EveryDrum.
It will be based on a STM32, and have at least 12 inputs.
This is still a work in progress, so I can’t say more about the project right now.

Conclusion

Hopefully, now you know a bit more about Ronna Technologies.
Even though most projects are e-drum related, I’m interested in a lot of other things.
Electronics and programming are my passions, and using those skills to make e-drum products is very rewarding.

I believe that e-drum product are usually way too expensive for what they really are.
A piezoelectric sensor is so cheap, and electronic components are also quite affordable, so why not make e-drums cheaper?
That’s what I’m trying to achieve with Ronna Technologies.
Hopefully, I’ll succeed and make great and affordable e-drum devices.