Don Iguano will be the most powerful pocket-format synthesizer yet

(while still running on batteries or Li-Po effectively)

Like his prehistoric predecessor, Don Iguano listens to the environment, able to recognize the faintest sounds. He knows which direction they come from. He collects those that sound interesting for later use in the composition. He howls and sings with you, creating a soundtrack of your day, and records everything digitally if you so wish.

What can it do?


Update August 2021

Testing the previous prototype revealed a few shortcomings. F1C200s does not have a FPU (floating-point unit, a co-processor that can perform fast mathematical calculations over decimal numbers with high precision), and it nees to use emulation. Or, all calculations must only use integer mathematics. And that's either slow, or cumbersome and limited.

There is a more advanced SoC in the family, V3s that features ARM Cortex-A7 running at 1.2GHz with NEON and VFPv4 extensions. And it has 64MB of DDR2 RAM, SPI bus for connecting display or external FLASH memory, plus two fast SD card interfaces. What's more to wish for?

Straying away from the Don Iguano concept, I decided to test the V3s in a slightly smaller pocket synth with the goal of emulating Mellotron and tape loops. It does not have a display or additional sound chip, the codec built in the SoC has very impressive specs: 16-32bit DAC with up to 192kHz sample rates, and 92dB SNR A-weight ADC running at 8-48KHz, with AGC & DRC. The sole disadvantage being that there is only a single ADC input channel. If this turns out to be a problem and we really want stereo sampling, we can add WM8988 for $3 extra.

This prototype keeps laser TOF ranging sensor VL53L0X, which is placed under two holes in top right corner, alongside the hand icon. The front panel is made from white enamel with HASL finish, in production it would be gold plated for higher contrast and better visibility of icons for connectors, which are under the solder mask and only add the texture (in these photos they are barely visible).

Because V3s uses a little bit more energy (~150-180mA), and requires 3 separate power domains from as low as 1.2V, instead of LDOs, DC/DC converters were used. Keyboard in this model has more keys than in Don Iguano. Four capacitive sensing ICs (ANSG08SH) were used, to which the CPU talks via I2C bus. These need to be configured for 4 different I2C addresses, and as I made error in wiring related to this, small corrections were required.

After assembling the capacitive sensors, accelerometer, LEDs and most of the other components, I2C test revealed that all peripherals are responding.


Update January 2021

In order to make it easier to work with the prototype, a front panel has been added. Below there is graphics design to compare with how it turned out in reality. A cheaper tin-plated option was selected, but in production it will of course be gold plated. Three status LEDs were moved to the upper left corner.

Sliders are now recessed too deep and hard to work with, they will need to be replaced as I don't see a feasible way how to add tiny knobs to them (stems are too short). Those two holes under the palm tree are openings for laser TOF ranging sensor VL53L0X (part number VL53L0CXV0DH/1), which was assembled and works very well.



Update December 2020

The F1C200s has internal codec, and the board has additional TLV320AIC3104 codec too, driven with I2S peripheral. I've added the headphones jack to test the internal codec first, the idea is that if it works well then the other one is redundant. I am often taking photos like this to remember which components exactly were used in which prototype board, it is invaluable later when comparing results and deciding what to use in production (and more reliable than random paper notes too! :)

Funny enough, in the default configuration the TLV codec and LIS3DH accelerometer ended up with the same I2C address, so the board had to be reworked a bit (to give the accelerometer an alternative address). One more mistake with the PCB design was forgetting to add two signals for status LEDs (SD activity and "heartbeat"), also what I thought was a "power good" signal from voltage regulator was actually "power error" so one more white LED was added to glow when powered on.


Update November 2020

The display was added, and seems to work. While I do not have selected a library for it yet, it can be tested simply by sending the initialization data and then some random patterns over SPI bus. Instead of I2C configuration, SPI was used as it is faster. Here you can see how fast can it refresh the first segment of the display.


Here is the back side, red wire is forgotten signal for Codec reset. You can also see how the display is configured for SPI (this is how it arrived, but if you have one configured for I2C it is easy enough to change it for 3 or 4 wire SPI. Also a microscopic detail of OLED pixels (a short video is here).


Update September 2020

I have assembled 3 of the prototype PCBs, to test alternative elements. It was easy enough apart from the CPU which was surprisingly reluctant to sit in its place, later I found out that the footprint is not perfect (lesson here is to never rely on someone else's libraries, always check everything! :) In the end, the first board appeared among USB devices as expected, waiting for the firmware (this is the FEL mode). I've uploaded an image taken from a Lichee Pi Nano board, just to see what happens, but as the linux there is not configured beyond the very basic functions, not much could be tested with it.


The second PCB was partially assembled too, and here it is being tested for booting from the SD card (which allows for more flexible and faster way for developing own applications). It took a few weeks to figure out how to compile own linux image, but in the end I was able to do it mainly thanks to these two great posts by George Hilliard and Nick Matantsev. The linux sources required a few patches to support F1C200s peripherals - which is easy thanks to good guys Icenowy Zheng and Mesih Kilinc - and the DTS file had to be updated too, to match pins assignment on my board.


On the third PCB a larger FLASH chip was assembled, with 128MB capacity. Although the very basic linux system can fit into 16MB, this should be enough for some samples storage too so the SD card is not needed all the time.


Update August 2020

PCBs have arrived! Ain't they beautiful :) Green solder mask was used (cheaper and faster) as this is the very first revision of the new circuit and it will surely contain some mistakes. All required elements are already here so the assembly should be straightforward.



Update July 2020

The previous design would end up being too complex and expensive to manufacture. I am trying to work with a more powerful chip to solve this problem.


Below is old information, last updated March 2019 (left here for comparison)

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Don Iguano is the world's first penta-core parallel polyphonic pocket synthesizer

Contrary to popular belief, the real Iguanodon didn't have a second brain. Our synth, however, does - which allows for some unique features.

Like his prehistoric predecessor, Don Iguano listens to the environment, capable of recognizing the faintest sounds. He even knows which direction they come from. He howls and sings with you, creating a soundtrack of your day, all the time... and records everything digitally, if you so wish.

What can it do?



Technical Specifications

Boasting an unprecedented 2500DMIPS of raw computational power, while maintaining the energy efficient operation, allows for development and application of strong DSP algorithms. Among the multiple features packed into the 67x39x20mm device you will find:

An open platform, featuring newest elements, driven by a well-maintained open-source software framework (ESP-IDF).


The Prototypes

Less than 7cm wide, fits comfortably into your pocket. Light enough to be worn on the neck too. Put it into a tiny trinket wooden box, Altoids can, or embed it into a 3D printed cyber brooch. By default, it is protected by a laser-cut Acrylic / Macrolon plate (photos coming soon).



Functional Block Diagram


Updated prototype

The newer, alternative prototype is larger. It features capacitive keyboard, speaker driver, two TOF laser distance measuring sensors and a 3D electrostatic sensor (which, as it turns out, does not work very well perhaps because the sensing area is very small). There are more buttons and LEDs, but the overall architecture is the same as previous iteration.

There were a few mistakes mainly with packages (some of these ICs come in more than one version), so the board will need to be revised once more.

This could be the future of pocket synth tech

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