Headless Dirtywave M8 embedded system client.
[!Important] Not yet functional - work in progress.
This project is comparable to laamaa/m8c except that it is based on an STM32 microcontroller running RTOS instead of microprocessor system that would be running standard OS like Linux, Windows or MacOS. Implementation on microcontroller enables creating a compact and power-efficient client system where the Teensy board, USB connection, display, keyboard and the audio interfaces could be fully integrated on a single board:
graph LR
D[Keypad matrix] ----|GPIO| B
H[PCM1802] ---|I2S| B
G --- I["Line Out (3.5mm TRS)"]
J["Line In (3.5mm TRS)"] --- H
B ----|SPI| C["Display (2.8'' TFT LCD)"]
B ---|I2S| G[PCM5102A]
A["M8 Headless (Teensy 4.1)"] ---|USB| B[STM32H7 MCU running m8ec firmware]
You could create custom hardware solutions where M8 headless would be integrated in an eurorack system in some interesting way...
Some pictures of my prototype hardware:
| Left Side View | Front View | Right Side View |
|---|---|---|
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- Video feed to the display.
- Keypad input.
- Audio input/output.
- MIDI input/output.
- PCB design with BOM list.
Some time around the spring of 2023, I discovered the M8 tracker on YouTube and immediately wanted to get one. As an embedded systems engineer, I was deeply impressed and inspired by what Timothy of Trash80 managed to create on the Teensy platform - huge respect for the guy!
Anyway, things like limited product availability, potentially high shipping costs to my country and my financial situation gave me doubts if I really buy the M8 🫠. These doubts lead me to experiment with the M8 headless firmware and the laamaa/m8c client software that is made to work with it. m8c is an open source project which got me curious how it interfaces with the M8 headless firmware, so I took a look at the code. I soon realized that making M8 headless client on a microcontroller might be feasible, and I already have basically all the hardware parts lying around. This seemed like a fun challenge, a great project to learn something new and also, potentially, a very exciting result for me personally - a portable M8 headless experience 😋.
Having said that, I understand that this project has the potential to do more harm than good to the Dirtywave and its creator(s). I'd be happy to discuss this project and its course with the creator(s) if it raises any concerns. I have no intention to compete or profit from this project and I want to be responsible and respectful to the original M8 hardware product.
I must admit, I really underestimated how difficult the USB par is going to be - it is not common to have a USB host on an embedded system especially with composite interface support for audio, CDC and MIDI.
First I tried the obvious, STM32's USB host library. It turns out it is quite limited and it basically has no proper documentation. I ended up modifying the library, for example, to support composite mode, and, later realized it's not worth the effort... Moreover, ST's state machine based USB stack implementation is quite inefficient so better use some more mature USB stack.
Moving on, there is this popular USB stack for embedded called TinyUSB, but it lacks the features needed to achieve full M8 headless functionality. So skipping that...
Next, I tried CherryUSB library and had some better luck with it. However, it lacks documentation and examples on how to implement audio class host applications.
So now I have kinda lost hope. So many hours spent on this thing...
There is maybe one more chance to get it all working - ThreadX's USBX stack which was made open source. There are these two guides on how to use it with STM32H7 (this and this). I guess I'm going to try that next if I will ever recover from the frustration of the previous attempts...