I am Rezzonics, the creator of DMFX-1, thank you for the interest you showed on DMFX-1 Digital Multi FX guitar pedal.
I think Axoloti is a great piece of equipment keeping a good balance of performance and simplicity. I think it's great that there is an effervescence of open source HW/SW initiatives like this and I hope there is plenty of room for other players because it can only enrich the DSP and Audio DIY community. I hope we don't see each other as competitors and I would like that some collaboration could be reached in the future.
I understand this is a community forum devoted to Axoloti but since there are several questions regarding DMFX-1 I would like to provide some answer to them, and I will be glad to answer any additional questions you may have.
DMFX-1 is based on TI TMS320C55xx 16-bit fixed point DSP. By playing with the ezDSPC5535 kit, which actually is quite compatible with DMFX-1 and allows doing many things, I realized that LCD and user interface limited a lot the audio capabilities of the DSP, that's why I decided to use two of them, one dedicated exclusively to audio tasks and the other dedicated to user interface, tuner, noise suppression and other no real time tasks. I could have chosen a cheap MCU instead of a DSP for doing this but that would require an additional development environment, so why not use an identical DSP, which cost less than 5$ that is able to deal with LCD, GPIOs, interrupts, I2C bus, digital potentiometers and everything required to manage the user interface?
Development environment is TI Code Composer Studio. License is free for XDS100v2 emulator environment that is what is actually used.
Code is developed in C language (or assembler if you are brave enough). By using good practice techniques, C optimizer can get good code efficiency results.
TI offers DSPlib with plenty of assembler routines for IIR, FIR filters and mathematical functions like sine, exp, log...
TI also offers a CSL library with lots of examples to implement peripheral interface control functions: SPI, I2C, LCD, GPIO, SAR ADC, interrupts...
DMFX-1 also uses DSP/BIOS provided by TI to deal with real time task management.
DMFX-1 will be certainly more expensive than Axoloti, I think it could be sold at 100€ to 125€, it consists of a 6-layers PCB main board and a 2-layer PCB daughter board.
It includes a preamp to allow direct connection of a guitar, output buffers and filters.
I also found that non-linear processing like distortion, overdrive and fuzz are difficult to implement in the digital domain, and not very efficient, so analog distortion circuitry is added.
Data can be routed via USB. The kit could include up to two SD cards.
I conceived this kit for DSP educational purposes or just have fun creating your own digital effects. Programming in fixed point may be more challenging, but I think that's actually part of the fun.
Latency on DMFX-1 will most probably be very similar to Axoloti: ADC/DAC codec latency plus the internal ping-pong buffer latency.
It would be interesting to see performance benchmarks: STM32F427 has 168MHz frequency while C55 has 100MHz, I guess performance will be mostly related with code efficiency more than processor speed. In terms of audio quality I think that 16-bits is more than enough, specially if final use is for guitar effects.
DMFX-1 is using 48kHz sampling, but I think that sampling frequency could be reduced without affecting a lot audio quality (for guitar effects at least) which could greatly improve efficiency.
Sorry for the spam and the long speech, I really enjoy this subject.