After my implementation of an SPI controlled DAC i was searching for an 14+ Bit Multiplying DAC. There were some from Linear but not available for an good price.
So here is my try to build an DAC in CS Style. (YM26600). This DAC creates an voltage output for each semitone. For the octaves there is an similar circuit with 6 switches (nit built yet).
For the first tests I started with 12 selected standard 100 Ohms Resistors. The 28.94k resistors are a combination of an 27k and a 25 turn 5k trimpot. I trimmed the pots as calculated in the simulation and it and the voltages where spot on. The switches are cheap CD4066s. To control them from my Arduino board i build the TTL to CMOS converters.
Here is a picture of the Digital Board with output Buffers an TTL to CMOS converter.
This is the Resistor Network.
This is the output Voltega for the Note B with a 4V Octave input voltage.
Here is the Schematic:
Discret DAC Schematic
I finished the Wiring to the DAC Board and the Arduino
Here a picture of the whole Setup
I wrote a little programm to test the whole circuit. It creates voltage steps in halftones.
Now i have built the Octave DAC. Schematic and coding will follow soon.
Here a short Video.
Source Code here
MidiToVoltage as .txt File
or on sourceforge.net
Added first polyphonic code
Midi to Voltage poly 1.05 as .txt File
This picture shows the multiplexed analog Voltage output. I am not sure with the timing for the following S/H stages. I think is code is not the best but it works.
Made PCB Layout in KiCad and thanks to the members of the mikrocontroller.net Forum for their help.http://www.mikrocontroller.net/topic/331468#new
Here is my last version:
will do some changes and will make one next weekend.
It is a single sided PCB. I will upload the final Version incl. KiCAD files if it all works fine.
Here the Schematic:Discrete DAC Schematic
Connection to the Arduino Board
- Building a Gate Out Circuit
Writing the Basic Midi to Voltage code
- Building an S/H circuit