Hello ! I'm happy (maybe even proud ;-)) to share this project with you.
It's a new improved Dekrispator synth ported on a more powerful dual core mcu development board : Discovery Kit STM32H747I-DISCO from STMicroelectronics.
There's also a new instrument called Desynkator which is like three metronomic sound generators synchronized in rational ratios tempi with adjustable probabilities. It shares the same controls and FX as Dekrispator. CC78 enables toggling between the two instruments.
It's an expensive board but I had the opportunity to get one for free but with a damaged LCD, so I could work on a version which would clearly separate USB and audio with the two embedded cores.
Of course, at that cost (about 100€), maybe a raspberry Pi would be a better option (less hassle with hardware configuration) but it's another universe !
More info on this synth here (project started in 2012 on STM32F407 MCU) : https://github.com/MrBlueXav/Dekrispator_v2/tree/dekrispatorV3
Sound examples for Desynkator :
https://polymerickblue.bandcamp.com/track/desynkator-i
https://polymerickblue.bandcamp.com/track/desynkator-ii
https://polymerickblue.bandcamp.com/track/desynkator-iii
-
Patch memory in QSPI Flash (save/load/erase all) : 32 locations currently
-
M4 core (at 200 MHz) manages MIDI USB Host function (stable with my old Korg NanoKontrol !) sends debug infos on UART and LCD, manages patch memory. Use CN1 to connect your midi device.
-
M7 core (at 400 MHz) computes sound.
-
No RTOS
-
Samplerate is 48kHz and audio samples are 16 bits large
-
CPU load is displayed (CM7 only)
-
Each core communicates through openAMP infrastructure and shared memory, small messages are serialized with Binn library (probably overkill).
-
MIDI Control Changes definitions are in a table of functions "ControlChangeFunctionsTable[128]" in MIDI_application.c file.
-
AUDIO_BUFFER_SIZE is defined in audio_play.h file.
-
Very basic LCD use at the moment, no touch-screen.
-
LED information :
- The orange LED reflects the CPU usage : when it's weak CM7 CPU gets overloaded.
- The red LED lights on when a system error occurs.
- The green LED indicates a midi usb device is connected and recognized.
- The blue LED indicates midi activity.
-
Debug messages sent with virtual com port from STlink (USART1 --> USB CN2).
PC Terminal configuration is as follows:
- BaudRate = 115200 baud
- Word Length = 8 Bits
- Stop Bit = 1
- Parity = None
- Flow control = None
I encountered endless issues to make this project work and suffered a lot... ;-)) I hope some people will find it useful and could use it as an audio synth platform !
It was first a STM32CubeMX project (the only way I found to reach that point) but can't be regenerated now, be careful ! I left the .ioc file for info only.
You should be able to import the project in STM32CubeIDE, I think all necessary files are in the repository.
There are also makefiles in /Release/ folder.
The background image for LCD (QSPI_Flash/Dekrispator-screen.bin file) should be written in QSPI Flash device with STM32CubeProgrammer application at address 0x97E8 0000 which is 1.5MB before end of memory.
Be sure to power your board with good PSU (> 1.5 A ?) especially with use of a midi controller, I had USB unstabilities because of unsufficient power in my PC plugs!
-
monophonic
-
sound generators :
- oscillators with very low aliased analog waveforms with superb minBLEP oscillators (thanks to Sean Bolton)
- 4 operators basic FM generator
- multisaw (several saws with individual "drifters")
- 10 sine additive generator
- noise
-
16 step random sequencer with variable length, transpositions, various scales
-
2 parallel filters LP/BP/HP with LFOs
-
1 ADSR enveloppe
-
Effects :
- vibrato
- tremolo
- overdrive/distortion
- echo
- phaser
- stereo chorus/flanger
-
random sound and FX patch generator
Special thanks : Sean Bolton, Perry R. Cook and Gary P. Scavone, Gabriel Rivas, Ross Bencina, Julian Schmidt, GaryA, Thorsten Klose, erwincoumans, ElectroSmith/DaisySP, ST, openAMP, Binn