Thoughts on the µPF--2 Z80 kit dev board.

 

In fact, when I look at the system I built, even though I did it based on compatibility with the original µPF--1 kit at the time, I realize that my version looks more like a microcomputer than a development board.

https://collection.onceuponabyte.org/ident/COMP-0156

At the time, when I studied with this machine, in 1987 I think, the PC was not yet very widespread. There was no adequate development software and furthermore the µPF - 1 did not even allow program loading through a communication port.

It was therefore necessary to provide all the hardware and software functions to allow the entry of mnemonics in assemblers, live editing and correction, memory modification, program launch etc etc ...

As my kit works, in fact I realize that I am exclusively using the C language, a PC text editor, and the SDCC compiler. Then, once the program is completed, I download it directly into the µPF - 2 and start the execution. I absolutely do not use the basic functions of the system.

So I made the decision to convert this set into a modern Arduino style development system but still keep the 'retro' side thanks to the Z80 hardware emulation. The entire development process will take place through the serial port via the standard tools available for PC.

The objective is to be able to train easily and in a fun way, not only in programming, but also in interaction with the outside world and finally that real applications can be managed by this system.

Multitech IOM board

I am therefore going to develop a first interface board like the IOM original board which will allow the µPF - 2 to be autonomous, capable of loading its application program itself, launching it and of interacting with the outside world in the manner of an automat. 

Do not hesitate to send me your comments.

Best to you.

Back to the 90s

At the time, I saw this kind of covers on certain magazines. There was something other than the extreme and boring standardization of Apple and Microsoft. 30 years of crossing the desert! A new start, I hope, for other things more eclectic and more interesting...

A SMALL MIDI TOOL (next)

Another problem that really annoys me when I want to quickly jump to a patch on a specific synth. is that it is never easy. You have to go to the PC to play with the mouse, or type on the series of control keys of a particular hardware sequencer. Or more simply, get up from your seat to change the patch directly on the machine.

I decided to create a small simple module allowing to select a MIDI channel as well as a change of patch on the selected channel.

Here is the result of my thoughts on the subject:

Unlike the Midi Merge Box project, here, the system must fit into the MIDI chain. The system cannot therefore be passive and must insert the patch change commands only when the MIDI 'network' is available.

The second challenge consists in power the Patch selector from the MIDI bus. Indeed, such a device which must be inserted in a MIDI chain can be very quickly painful to use if in addition it is necessary to manage the power supply unit.

To do that, it is necessary to develop a system whose power consumption remains below 20mA, ideally below 15mA. this time, I chose a microcontroller that I haven't used for over 15 years but which turns out to be very energy efficient and above all very easy to program / debug.

At the stage where I am developing my little studio, I have now to decide for a mixing console. I would go for a RACK version because I don't have a lot of room in my studio!

What do you think of Yamaha's TF-R rack console?

Tell me if you have any comments on this console ...

Time for the µPF--2

 The µPF--2 

When I developed this µPF - 1 / B compatible board, I wanted from the start to add a specialized time management circuit. So I installed a DS3231. This circuit is interesting because it is very precise. It also offers RESET management that I used as a master reset of the board. 

This DS3231 operates using the I2C bus. Obviously, this bus must be implemented in the FPGA. That shouldn't be a problem. I thought I would find a usable 'piece of code' on the web. In fact it was not a good idea. The codes found are often complex and above all undocumented.

Therefore, the best solution was to implement the I2C protocol myself. That's what I did. It is not very complicated, but not necessarily straightforward.

After a short period of development, I got the bus to work perfectly and was able to configure and read this real time clock circuit:

At this point, I have tested all the hardware functionality of this project. I also rewrote a lot of the system. It only remains for me to integrate all these developments in a 'clean' way.

I am beginning to see the end of this subject ...

A SMALL MIDI TOOL!

 A few days after having ordered the realization of my printed circuit board, it has just arrived:

A very easy to assemble midi merge box

Unlike usual, I chose not to use SMD components but only through hole components. This will make it easier to assemble the circuit. I could even offer the circuit to be assembled as a kit if that interests some...

I am still waiting for the components, especially the switches and connectors, to carry out the first tests.

A SMALL MIDI TOOL!

A midi merge box

• Current synthesizers are now often equipped with software allowing their setting from a PC / MAC.
• For those who prefer hardware sound generators rather than software, the number of machines to be controlled tends to increase over the years.
• The topology of the MIDI network is not efficient when it is necessary to connect several MIDI out to a single MIDI in.
• Several solutions are available to overcome this problem but often it does not work well but still costs a 'certain' price.

In order to meet all these challenges, a few years ago I bought a USB / MIDI interface with 8 MIDI IN / OUT ports. Unfortunately, the management of MIDI information passing from external machines to the PC / MAC was buggy. Only 16 bytes were correctly treated. Longer messages were not transmitted correctly. Impossible then to download a complete set of patches.

Since I'm tired of buying unreliable devices, I decided to create my own very simple interface:

This interface is passive. That is to say that it does not control the MIDI packets arriving on the inputs to transmit them on the single output. 

This implies a single operating constraint: a single external device must send data at a given time to this interface. If the connected devices don't emit anything until you ask them to, that's okay. 

If a device continuously emits real-time information for example, and it is impossible to prevent it to do that, it is sufficient to easily disconnect it from the box, using the corresponding switch.

And the MIDI DIN5 sockets... I hate them. So I installed 3.5mm jacks for easier handling. It will obviously be necessary to make suitable cables but it is easy to do.

RETRO ][ : A Retro Apple 2

The adventure goes on. After having assembled an Omega MSX2 computer, an Easy Z80 under CP / M and a Maximite under Basic, this time I am attacking a clone of APPLE2, the RETRO] [ :

https://www.hackster.io/news/capture-apple-nostalgia-with-the-retro-computer-f0fc0ffda886

After starting by mounting the power supply, I actually noticed a problem with the two negative voltages of -12V and -5V. 

Both of these power supplies have a small design error. Nothing very bad but this implies on the one hand not to mount the two regulators concerned, as can be seen on the previous picture, and on the other hand to make the corrections to the printed circuit board.

This considered, nothing prevents continuing to build what will ultimately only be a prototype since a final version involves making corrections :

Nice board however!