CSQ-600.

 A few years ago, I acquired a Roland CSQ-600 sequencer in very poor condition and downright out of order.

I have been troubleshooting this machine for some time. After some investigation I have only found one broken LED so far. 

However, I still find it completely impossible to start the CSQ-600. On the oscilloscope, the processor seems totally frozen. No scanning is performed on the buttons for example. So I suspected a problem with the processor.

I therefore bought on eBay a new processor equipped with the correct firmware. After replacing the old processor with the new one, the result is the same. The CSQ does not start.

So I wondered if the processor bought on eBay was indeed well programmed. But how do you know?

After some research, I discovered that someone had developed a small board capable of programming and reading this type of CPU.

All the information for the realization of this board is available here. So I made a copy of this programmer. The author has slightly modified the layout of the components but the operation remains the same. 

This material is used with a small software allowing to read and program a certain number of old circuits of which the 8048.

So I performed a memory dump of the two processors, the original one, and the one bought on eBay. What was the result?

Well the dump of these two circuits is strictly identical.

However, I noticed a rather strange phenomenon. After a few tens of seconds, the original 8048 of the CSQ-600 gave absolutely anything during new dumps.

While researching CSQ-600 troubleshooting info, I had occasion to read comments that the processor seemed to have this kind of problem. That is to say that when it was powered, a few tens of seconds later, the dump began to 'spin'.

I performed the test myself by cooling down the CPU and then testing it again. Indeed, after a few tens of seconds, the dump is no longer valid.

Ok, I've made some progress on the subject but... that still doesn't tell me why the CSQ-600 won't start!!! I got a disassembler, so I'm going to study the ASM source to see if the CPU does any test before starting the application. I will also try to test its start cycle with the logic analyzer.

What seems obvious now is that it is useless to perform these tests with the original processor. It definitely looks faulty!

And in fact, I also now own the binary code of the processor....

Gowin FPGA

 I just received the PCBs for testing the Gowin 144 pin FPGA :

Yes, seen like that, it's not very 'sexy'. But hey, it will be, I hope...

The problem of front panel prototyping.

With the development of my MIDI switch, I am as always confronted with the mechanical realization of the case. The problem is that I have made good progress in the development of the MIDI switch and I would like to put it in a box. It would be much easier to develop the software, rather than having a whole bunch of modules on the workbench.

But it is not at all easy to find a manufacturer able to produce a front panel at an acceptable cost. In fact, I never found one. 

So, I decided to see if I could use the CNC that I own but have never used. I have owned this Colinbus since 2007, following an article by Elektor :

In fact, for lots of reasons, I never assembled this machine until 2016 or 2017, I'm not sure, where I started assembling it. And then I found myself confronted with the problem of the electronic control board. It was a proprietary board, so you had to get the proprietary software, which I couldn't do. 

It must be said that this machine was no longer offered for a long time and that its electronic board was no longer able to communicate with the manufacturer's current software. So I decided to switch to a more current and above all more standard control board, I opted for a TinyG board from Synthetos :

And, in 2020, thanks to the first confinement in France, I took the opportunity to finalize the assembly of the machine with this new control board I wrote an article about it in French here. I was able to test the machine with the new board, as well as control software whose name I no longer remember. 

But it wasn't working correctly. the X and Y movements were unable to realize the extent of their theoretical displacement. 

Despite a whole series of tests, I was not able to find the cause of this malfunction. I assumed then that it was either the software, or the power of the laptop used, or mechanical alignment problems that prevented the correct operation of the CNC.

I dropped the case again until a few days ago. It must be said that I am really motivated to create a correct front panel for my MIDI switch. This time I used CNCjs. And I also changed the USB cable that I originally installed in the CNC :

And then, I don't know why, everything started working fine. I was able to move all three axes with no problem. The use of the keys of the keyboard for that allows precise and fast test. The only small problem is that I found that the machine generated a lot of extraneous noise, some of which seemed to me to resonate. Which is not good for the precision of the machine.

But, after having checked and perfected the tightening of all the screws of the machine, these parasitic noises have disappeared. So it looks like I am now able to perform drill tests with this machine. I still have to find suitable end mills as well collet chuck for the milling motor. 

Because when ordering the machine, I also asked for a slightly more serious motor than the original one, but was obviously delivered without collet chuck : Optionnal :-(

In short, fifteen years later it seems to me that I have never been so close to finally using this CNC. Hoping that the final precision is correct, even if for my work on the front panel I don't need great precision. 

The CNC, once well adjusted and tested with CNCjs:

MIDI SWITCH.

We do tests on prototype boards, we develop ideas that don't always work. And then at some point, when the concept is in place, you have to connect everything to check that the general idea can work.

what is called a 'noodle dish'

Between the different programming systems, those allowing various logging methods, the USB hub is very busy. And finally, the realization of the first MIDI 'ping'.

The principle is simple:

- We start from the PC in MIDI.
- We enter the MIDI information to the SWITCH.
- We continue from the SWITCH in MIDI to a synthesizer.

And yes: it works!

At the same time, on this path, various changes of media type and communication speed are performed. This is the principle. And the general principle is to make a machine that facilitates MIDI interconnections. 

I seem to be on the path I have set myself. Obviously, there will be 16 channels to manage. For the moment I am not yet able to know if the power of the integrated processor will be sufficient but I think so, it works at a fairly high frequency...

Shortage of components :-(

It is clear that, although the economy has supposedly recovered, the availability of certain components is still uncertain. As for those that are available again, prices have increased significantly.

This is the case with FPGAs. However, for particular creations, I appreciate the use of FPGAs. I intend to develop my Drumulator clone with this type of circuits. 

And, suddenly, I'm not really sure I can get the modules that I use. So I decided to make an FPGA module myself with a circuit made in China by Gowin.

For now, the goal is to create a test module that can allow me to discover these new circuits. They are not really comparable to Altera (Intel) or Xilinx circuits. They offer less possibility, a priori, but should perfectly suit my basic applications which do not require large resources.

So I chose to use the GW1N-LV4-LQ144 component. It offers 4608 LUTs, 180Kb (22.5 KB) of BSRAM and 256Kb (32KB) of FLASH. I think this should be enough for a minimal Z80 system implementation like that of the Drumulator.

But, to be clear, I'm not sure of anything at the moment... So, as I like to experiment, I developed a small module-type board which, if my tests are conclusive, can be used for a few applications:

Front

Back

The board seems more 'simple' than what we are used to seeing with classic FPGAs. It is precisely that Gowin circuits allow this simplicity. And I like it when it's simple ;-)

I still have the silkscreen to be placed correctly and I will have some printed circuits made.

That's good, I received a Gowin programming dongle this morning:

Let's go for adventure ;-)

OMEGA MSX : Other projects

Around this OMEGA computer project initiated by Sergey Kiselev, there are other contributions that I think are worth mentioning. 

First, a series of expansions made by Msxmakers, including a 4Mb static memory expansion card. This extension is intended to take place directly on the OMEGA connector, in the space provided for this purpose:

This extension seems interesting to me because it offers enough memory for the development of ambitious projects.

And now a new version of the original Omega board, this time made by Merlinkv and available on the dedicated Github page. The main purpose of this new edition consists mainly in improving the routing of tracks, especially those dedicated to the video part. The goal is to significantly improve the quality of the video output:

Other significant points: The original ROM slot in DIP version has been replaced by two slots in PLCC format, allowing the selection of several types of capacity. All of the decoupling capacitors and other non-chemical capacitors have been converted to CMS format on the back side of the board. Finally, a number of additional connectors allowing the selection of the ROM, the external Reset of the system, and other possibilities of power supply and connection of fan were added.

You can find this information on the Spanish forum: https://www.winuaespanol.com/

If you are interested in MSX type machines, I recommend that you subscribe to the associated Facebook page: https://www.facebook.com/groups/msxhomecomputers

I haven't tried these two projects since I'm currently working on an MSX-ROM type cartridge project that can be downloaded by USB. And this kind of project already takes quite a bit of time...

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...