Kerberos 2

[Frank Buss]

There are problems with some of the parts for the current version of the cartridge. For example the CPLD did cost $2.50 when I initially designed the cartridge. Nowadays it costs over $20, and no distributor has it in stock, with half a year lead time etc.

So I'm planning a more modern version currently with more memory, better FPGA etc. See the github page for the currently planned parts:
https://github.com/FrankBuss/kerberos
All parts are in stock with 1000 or more pieces, hopefully until I finish the prototype. The FPGA is also powerful enough to emulate the current MC6850, so no need anymore for this DIP IC, which makes production easier as well.

I imported my old Eagle project in KiCad for it, for the PCB outline and positions of the reset button, DIN connectors and LEDs, worked pretty well. Then I added the new parts for a placement test. Looks like there is still lots of space, but needs level converters and voltage regulators. But shouldn't be a problem. And all parts are easy to solder, in case someone wants to build their own cartridge, except for the microcontroller which is QFN, but can be done with solder paste and hot air gun for a prototype.

A major new feature is the USB port. This will allow easier and much faster transfer of data to the flash and the RAM than over MIDI, and will have less problems, unlike with the current version, which doesn't work with some MIDI adapters.

It will also have 16 MB RAM. In combination with the more powerful FPGA, it should allow to emulate a 16 MB REU, so it should be possible to play NUFLI movies with it, or to use it with Geos etc.

BTW, I used an USB-C connector. I like that it is rotational symmetric, easier to plugin a cable. Or is micro USB better?

I guess I can finish the circuit in a few weeks, and then maybe 1-2 months to update and enhance all the software. There will be a test phase as well, where I send prototypes to users who can test it on many different computers, or MIDI equipment. Production will need some more months, but maybe it will be available again end of this year.

Current version for a placement test:

[Matt McArdell]

Great news!

Regarding the USB port, any chance of this supporting midi over USB?

[Frank Buss]

What function do you need? It should be possible to make the Kerberos act as a MIDI device and I will test this. This means you could connect it to a desktop computer, like a PC or Mac, and then for example use a sequencer software on PC/Mac to play notes in cyntCART.

Not sure if the other way is possible, like connecting an USB MIDI keyboard to the Kerberos cartridge. If not, it would be still possible to route the keyboard input through a desktop computer to Kerberos, or with a Raspberry Pi etc.

[Matt McArdell]

Even as a usb device would be great - makes it simpler to connect up an ios device or other host for more complex sequencing without midi din. For my main setup, I do have a raspberry pi zero setup as an all pass through midi usb host which allowed me to avoid having to daisy chain about ten keyboards, controllers, and synths.

As a USB host would be nice however - being able to just connect a compact a midi keyboard controller (which are often USB only), would be handy, but I note that USB host capability isn't that common in smaller "synths". As you say, you can always use some other usb host, but it just requires more parts to connect up and configure. Or else just just us a larger midi din keyboard/controller.

[Frank Buss]

Looks like host mode is possible:
https://forums.raspberrypi.com/viewtopic.php?t=305467
But I would build the cartridge like the Pico, so it can't power USB devices and would need an external powered USB hub, because USB can source up to 500 mA, and this is too much for a C64 to be safe. But at least better than some big Raspberry Pi or PC.

[Matt McArdell]

Yeah, my rpi zero host has all the devices plugged into a powered usb hub and it would be fine for the C64 just to add to that as another device - for a permanent setup, the device mode would be great! FYI Here's the rpi setup instructions I followed: https://github.com/sinedied/pi-midi-host/blob/main/README.md

It's pretty compact, but just another little box to connect up or move around.

The main benefit of the kerberos acting as a host is probably more for ease of use with a single low power keyboard/controller. The kind you'd normally plug into an iphone without needing external power. I agree though, if it was "easy" enough to add host capability to the kerberos, then all you'd need externally is the powered usb hub and no raspberry pi/other box and this would make it easier to connect keyboard and knob controllers etc. at the same time.

I'm planning on using the future kerberos with an Ultimate64 elite (I likely have a bit of a wait on that) which I'm thinking of putting into a custom 3D printed case to make it masquerade as a smaller synth/cyberdeck, possibly integrating my small encoder controller (for midi CCs), and the little usb midi keyboard. I can dream of course :)

[Frank Buss]

I think the circuit diagram is mostly done now. Here are the KiCAD files:

https://github.com/FrankBuss/kerberos

Export as PDF:

https://github.com/FrankBuss/kerberos/raw/master/kicad/kerberos2.pdf

It is a lot of parts, looks like this:

Wouldn't fit on one side, but this is mostly because of all the test headers, and for example I added a current measurement circuit, and can decide with the jumpers if I want to measure the current of the 3.3 V voltage, or for the 1.2 V core voltage of the FPGA, to check if the voltage regulators are sufficient, and if it doesn't damage the C64. The OpAmp and hall effect current sense chip will not be on the final board.

I think I will create a bigger board for testing and developing the new firmware for it, usually the first board after so many changes has bugs anyway. Will finish it in one week, next weekend. Feel free to take a look at it, write here if you find some bugs, or if I can improve things.

[Richard Faulkner]

Can't tell you what's right or wrong - just a friendly note of encouragement. Love your first kerberos!

[Merlin Massart]

Off all the midi/synth cart for the c64, this one is the most interesting. Hope it will go to an end!

Are the actual files already working as they are? In other word, could I order a pcb as it is to build my own right now?

[Frank Buss]

It is the first prototype with the new parts, has probably still some bugs. I'll get it in a few days, then I can testing and developing the new software with it.

[olivier bernhard]

I really hope you can get a final working version ! I have been chasing this fantastic device since a very long time on Protovision web site :)

[John Anderson]

I love my Kerberos - just learned about this, V2 seems amazing for music and more.

[Alf Marius Foss Olsen]

Any news on this Frank?

Whenever this is ready I'll be first in line, along with a good bunch of people I recon. Can't wait! :)

[Joss Wright]

Just another desperate C64 user wondering what the status of the new Kerberos cart is! I'd love to get my hands on one of these!

[James Hleba]

I am very excited for these to be available as well. I have been hoping to purchase the 1st version for almost a year now.

[hExx]

Count me in too!  I've been keeping my eyes peeled for the v1 cartridge.  Willing to buy a v1 cart if anyone is selling. :)

[Chuck Itall]

I am salivating over this to be available....Any news??? I have PROJECTS to create!!!!!!

[Nils Köpke]

Hope you are well and the project still going well. Really looking forward to get the Kerberos V2. Whenever I planned to get the V1, it was sold out or still not available. Maybe a chance to be on a preorder list for V2? I would even love to pay early, to help to get it "done".

[Frank Buss]

I'm still working on it, but pretty busy with my main job and other work, so I don't think I can finish it this year.

[metro_]

Thank you for responding!  

Despite the time that has passed I'm happy to read that you still intend to carry on. I'm also one of those at the edge of my seat hoping for this to materialize :)

Are there any areas where the community could be of help?

All the best ~

[Who Cares]

Ooooooh waaaw. I've been searching everywhere for one of these. I do hope a new batch is in the offing. Cheers from Belgium.