Motivation
This is the software driven replacement for my all hardware pitch to voltage converter (link) from my Shakuhachi to Synth project. The software driven approach has the advantage of easily adaption for different frequency ranges. In my case it is the range of the Shakuhachi. To change the range just adapt the software. It is completely temperature independent. The needed input is a pulse train derived from your original signal. You can use my Signal to Trigger converter to provide the pulse train. An offset voltage is added to the V/Oct output to fit the needs of your VCO (Synthesizer).
Specs and features
- Software driven pitch to voltage converter
- 12bit resolution
- V/Oct output
- Offset CV Fine and coarse adjustment
- Runs on +/-15V and +/-12V
- Power consumption around 45mA positive rail, 15mA negative rail
Implementation
Schematic
Pitch to voltage converter: Microprocessor board schematic
Pitch to voltage converter: Control board schematic
Description:
The incoming pulse train is feed to the microprocessor. IC1 (301-F) prevents the microprocessor from negative inputs. Zener D2 prevents from overvoltage. The trigger starts an internal timer of the microprocessor in input capture interrupt mode. The ticks are counted and the count is then looked up in a table. The lookup table provides the values for the V/Oct conversion. The read value is the send to the DAC MCP4921 which is follwed by a low pass (IC1A, 301-B)). IC2A (301-F) adds the offset voltage and IC2B (301-F) corrects the phase.
Calibration
- None
Building hints
- The AtMega 328p is running on 20MHz. You have to set the right fuses.
- - avrdude -p m328p -c avrisp2 -U lfuse:w:0xe7:m
- - avrdude -p m328p -c avrisp2 -U hfuse:w:0xd9:m
Special parts
- None
Download
Pitch to voltage converter control board documentation downloadPitch to voltage converter control board Gerber files download
Pitch to voltage converter microprocessor board documentation download
Pitch to voltage converter microprocessor board Gerber files download
Pitch to voltage converter *.fpd file download
Pitch to voltage converter software files download
Pitch to voltage converter: Front view
Pitch to voltage converter: Populated PCB
