Keymatrix to single input

I have wired the keyboard as a CV monophonic keyboard. The output from the keyboard goes to an analogpin on the Arduino.

I wont even nee…

I wont even need a DAC on the Arduino.

I’ll run PWM on port pin11 with 60KHz to get 8-bit analog output.

So still no extra hardware on the duino.

I have a couple of digital filters but I think they will be unused.

Just get the right waveform and we will have the SuperSaw.

The keys

The keyboard I’m going to attach to this baby Arduino Nano is a 37 mini-keyboard with a 5 x 8 matrix.

What is a SuperSaw wave or sound?

Well, there are as many answers as people answering the question.

The basics is called phase desync or simply chorus and there are many ways to achieve the same result.

The simplest is to use a number of detuned oscillators.

You can use a tight chorus modulated by an LFO.

It can be done with PWM of a sawtooth.

I havent decided yet on the method but I’ll do it for sure.

SuperSaw Synth with the Arduino

Hi all.

I’m back after 3years of writing firmware for heatpumps.

Got tired and wanted to do a synth again.

I have always liked the Roland SuperSaw trancesound of the JP-8000.

As I already have a lot of synthesizers I just need that small tabletop synth to give med those nice leads and pads.

How do I get that?

The Arduino

Back in business

So after having a lot of other things that had to be done, I got some time over to continue the project. First I had to cut the 29 potaxels down to 12mm (1/2 inch) to fit the knobs.

I then started to mount them one by one on the frontpanel.

As I tightened the nuts I managed to make some small scratches in the panel but I can live with them as they are not that obvious.

Whohaa! A whole forest of pots. This will require some amount of wiring I guess.

And finaly the pots and knobs mounted.

This time the pictures are not a simulation but the real thing.

The next update will be the LCD-display and a rotary knob for patch/parameter change.

Until then…

/Jan

Cold in the north

Sorry for not making any updates lately but I have to work on the house heating and it’s getting quite cold here in Sweden. I promise I’ll be back as soon as I have a warm home.

/Jan

Some progress and a binary tutorial

Ok, while waiting for the hardware to arrive, i’ve made some progress.

I had a comment regarding my schematics and how come both the left MUX, the right MUX and the LCD are all connected to the same wires in the LPT port. Is that gonna work?

Yes it will, it’s all down to binary numbers and how computers “talk” to different chips on the same wires (in parallel). It’s called a databus.

But if they are all on the same wires, won’t there be collisions? No, because we have something called a chip select (CS or E signal).

All the chips listen to the same bussignals in parallel but only the chip that receives the chip select signal will use the data on the bus and the A/D converter and the LCD have their chip select on different lines.

There was also a question about how an Inverter can be used to select between the left and the right MUX.

A value of 0-15 are represented with 4 binary digits (A0-A3 in the schematics)  so we can use that to select one of 16 inputs in both multiplexers in parallel.

What happens when we output the number 16? Well the 5th line goes to a logic 1. This means that the left MUX will be disabled because the E input of the MUX needs to be a logic 0 (or off) for the MUX to let anything through. So by putting out the number 16-31, the left MUX will disconnect but at the same time the Inverter will “Invert” that logic 1 to a logic 0 so that the right MUX will put it’s voltages through instead.

This means that from 0-15 the left MUX delivers and from 16-31 the right MUX takes over. Easy or what

Then for you that understands exactly how it works also know that when putting out values to the LCD the MUXing will jump around like crazy but that doesn’t really matter as we are not reading any values from the A/D converter because it’s chip select line is off.

I know this is technical but if you build it like this there will be a minimum of wires to connect and it will just be a matter of putting out the right values to the LPT port.

/Jan

Analog scanning and display hardware

These are the hardware chips that will be responsible for scanning the potentiometers.

2 x  CD4067 16 to 1 Analog Multiplexer

1 x TLC549 8-bit Serial A/D Converter.

The multiplexers will enable the PC to choose 1 of 32 analog inputs for A/D conversation by the TLC549 A/D converter. The endpoints of the potentiometers are tied to +5v and Ground and the center of each are routed to an analog input of the CD4067. The frontpanel program scans through each of the pots and registers any changes, transmitting these as MIDI-CC.

The display part is a standard 20×4 LCD with a yellow backlight connected to the PC with a 4-bit interface enabling the frontpanel program to display any characters or graphic on it.

The display is very easy to interface with thousands of examples on the Internet.

The frontpanel buttons are connected to the standard PC-keyboard scanner resulting in normal keypresses to the frontpanel program.

Here is the complete schematics with the 4 chips and display connected to the parallelport.

The 4th chip is just an 74LS04 Inverter used to extend the adress range for the multiplexers to 5bit linear adress  instead of 4bits per chip.

There is actually a bonus using an A/D converter, it converts analog voltage to a MIDI-CC so if we would like to have a CV input, no problem, just connect a jack to one of the multiplexer inputs. It’s that easy.

/Jan

Measuring the Panel

I have been busy printing and cutting out the panel vinyl. Actually it’s mostly CAD work, making sure that the finished vinyl keeps the original measures.

The blue spots represents a 10mm potentiometer and the orange spots a 6mm button. I also have to make a large hole for the 20×4 LCD display.

I still don’t like the compact-flash sticking out so I’ll just ignore it. When I’m done I’ll mount it inside and patch up the hole.

/Jan