Drumulator Clone...

That's it, I've pretty much placed all of my ideas regarding my recreation of the Drumulator. I obviously added some goodies compared to the original machine.

Now I have all these components to place on a PCB:

Hmm, that's not my favorite part of the job...

[06/09] After a few hours of work, here is the general idea of ​​the front panel:

You will have understood, it's new, but old style version, because... I like that too.

[06/15] There's always a moment when you wonder if you're going to make it!

Anyway, I continue to place the components. It only remains for me to place those dedicated to the 'simple' output filters and as well as those dedicated to the commands/display of the machine :

Like that, it seems clear and well arranged, but what will be the routing with all these signals!!!

[06/16] After a few more hours of work, it becomes clearer...

3D visualization, even if it is not perfect, still allows you to get a fairly close idea of ​​what the printed circuit board will look like:

All you have to do is try to route all the connections. It might be 'sporty'!

Drumulator : It's progressing

There it's done. The audio output tests I'm preparing for my Drumulator clone works fine.

I present to you the prototype of the audio output of my new Drumulator:

And, in order to demonstrate the perfect functioning of the board, here are a few seconds of video. 

(Click on Youtube to have more details)

For the moment I don't have a suitable camera but I was able to use DaVinci to select only the clearest part of the video, and export it to Youtube. You have to start by testing the tools at least before embarking on large publications...

Drumulator in FPGA & OMEGA MSX computer.

THE DRUMULATOR

I continue the experiments of recreating the audio outputs of the Drumulator.

At this stage, I know that I am able to read all the Drumulator sounds correctly with the digital/analog converter used, once the data has been passed through the decompression table to the µLAW standard.

But, for the moment I reproduce the sound directly at the output of the audio converter. I now have to test on the one hand the individual volume adjustment part then the sample&hold outputs, in order to verify that the reproduction is going well on all the outputs.

It's a bit complicated because in order to minimize the need for board routing, I opted for serial interfaces for all the commands. Originally, the interfaces are of the parallel bus type with all that this implies of buffer circuits and bus locking.

And above all, I like to condense ;-)

Apart from the analog converter and the serial control circuit, I use the same components as those present in the Drumulator, just to preserve as much as possible the sound signature of this machine.

THE MSX OMEGA

This morning I received a package directly from Poland. Even if I blurred some information on my home address, I note that the French postal service still retains within it, some real clairvoyant eyes. I doubt that it happened correctly in the machine-reading system... Long live to the world of real people!

And what's beautiful inside this 'survivor' package? 

Everything you need to build a great case for the OMEGA board. All I have to do is find the few screws needed to fix the board to the bottom of the case. Interesting thing: I find that my USB to OMEGA keyboard conversion interface fits perfectly inside the box without any problem. I should even have room to attach a USB connector to the front panel. From the cutout informations, I thought my interface wasn't going to fit inside. In fact, it does it very well and I'm very satisfied!

The difference in this version is that there is no cutout for the Omega keyboard as originally planned since I am replacing it with a USB keyboard. I indeed thought that it was not going to be practical to type on the keyboard placed in the high position. I was right. It will be much more practical with a 'normal' keyboard.

So, I'm thinking about building a cartridge to easily develop software for the Omega. I know that there are many solutions, including the one that consists of using a ROM cartridge of the MSXROM512 type from Raphnet, on which we place an EPROM emulator to easily upload the code, once validated in the emulator,

but I am going to try to develop a cartridge that can be loaded natively via a USB port and also equipped with a serial port. 

Because in fact, I'm not very 'games' with computers but rather communication. I would love to connect this Omega somehow to the NET.

Many thanks to Krzysztof Odachowski for the realization of this enclosure...

Drumulator in FPGA & MSX news &...

It's been a few weeks since I posted anything. However, I worked on four simultaneous subjects.

• Troubleshooting the CSQ600.
• The development of the MIDI switch.
• The finalization of the USB keyboard converter for Omega.
• The test of the audio output of my future Drumulator. 

CSQ-600: 

Unfortunately, I couldn't get the machine to work. However, I installed a new processor, but the result is strictly identical to that of the original processor. I just managed to have a different start of the machine by replacing the original oscillator with a signal generator. The result is insufficient for me to get an idea of ​​the problem for now. After a few days of intense investigation, I momentarily put the subject on hold.

MIDI SWITCH :

I made some progress on the subject. I mounted a module with four RJ45 inputs/outputs as well as a small conversion 'pod' to MIDI IN/OUT. I'm currently stuck because I can't get my hands on the small processor used on the PODs. Fortunately, I recently found availability for this processor and ordered a few copies. I am awaiting delivery.

USB KEYBOARD CONVERTER :

I am pleased to announce that the development of this interface is finished. I finalized the code for 'AZERTY' and 'QWERTY' type keyboards. As a reminder, this converter allows you to connect a standard USB keyboard to the MSX OMEGA microcomputer. Also, I'm waiting for some components to manufacture a few copies that I will make available for sale for those who wish to go through this solution rather than building the OMEGA keyboard entirely.

The Omega computer

AUDIO OUTPUT FOR MY FPGA DRUMULATOR :

I completely coded the processor part as well as the waveform sequencer in VHDL. The goal is to fit as many logic elements of a Drumulator as possible within an FPGA. So I still had to study the audio output. 

The problem is of course, that the kind of digital to analog converter used in the Drumulator is absolutely no longer available. The solution adopted therefore consisted in using an available 12-bit converter, and in coding the system making it possible to reproduce the logarithmic transfer function of the original converter.

For this, I started to mount a copy of my analog output prototype:

Quick & dirty test plateform but sound very good!

To do my tests, I used a development board from STmicro equipped with a fairly powerful STM32 processor. This kind of board associated with the ST development software is really ideal. Once the system was set up, I encoded a square signal at 1KHz using Audacity which I exported in µ-LAW format to the development board. The result gives what was expected:

For this kind of test, low precision required and low frequency, the (toy) FNIRSI-1014D is ideal because it does not generate any fan noise. This allows you to leave it on for hours without wanting to throw it out the window at the end of the day ;-).

Finally, I replaced the sinusoid definition file with the one from the copy of the original Drumulator ROM to see the scrolling of all the sounds of the machine, given that I scan the whole 64K of ROM.

In fact I obtained the same result as that obtained by testing the waveform sequencer implemented within an FPGA, by directly sending the addresses to the ROMs present on the motherboard of the Drumulator test:

Basically, I have 'proof' of all the important parts of the Drumulator working. It only remains for me to test the analog output filters, knowing that there are recent components to replace the old SSM present in this section of the Drumulator. Each part works 'in its own corner'. Now it's all about putting it all together on a large prototype board.

I left my job with the madmen of the French national education since a few weeks, and life is much more pleasant now. I develop what I like, at my speed... Peace for ALL!